Lysine-ε-acetylation (Kac) is a post-translational modification (PTM) that is critical for metabolic regulation and cell signaling in mammals. However, its prevalence and importance in plants remain to be determined. Employing high-resolution tandem mass spectrometry, we analyzed protein lysine acetylation in five representative Arabidopsis organs with 2 ~ 3 biological replicates per organ. A total of 2887 Kac proteins and 5929 Kac sites were identified. This comprehensive catalog allows us to analyze proteome-wide features of lysine acetylation. We found that Kac proteins tend to be more uniformly expressed in different organs, and the acetylation status exhibits little correlation with the gene expression level, indicating that acetylation is unlikely caused by stochastic processes. Kac preferentially targets evolutionarily conserved proteins and lysine residues, but only a small percentage of Kac proteins are orthologous between rat and Arabidopsis. A large portion of Kac proteins overlap with proteins modified by other PTMs including ubiquitination, SUMOylation and phosphorylation. Although acetylation, ubiquitination and SUMOylation all modify lysine residues, our analyses show that they rarely target the same sites. In addition, we found that “reader” proteins for acetylation and phosphorylation, i.e., bromodomain-containing proteins and GRF (General Regulatory Factor)/14-3-3 proteins, are intensively modified by the two PTMs, suggesting that they are main crosstalk nodes between acetylation and phosphorylation signaling. Analyses of GRF6/14-3-3λ reveal that the Kac level of GRF6 is decreased under alkaline stress, suggesting that acetylation represses plant alkaline response. Indeed, K56ac of GRF6 inhibits its binding to and subsequent activation of the plasma membrane H+-ATPase AHA2, leading to hypersensitivity to alkaline stress. These results provide valuable resources for protein acetylation studies in plants and reveal that protein acetylation suppresses phosphorylation output by acetylating GRF/14-3-3 proteins.
Agricultural production is hampered by disease, pests, and environmental stresses. To minimize yield loss, it is important to develop crop cultivars with resistance or tolerance to their respective biotic and abiotic constraints. Transformation techniques are not optimized for many species and desirable cultivars may not be amenable to genetic transformation, necessitating inferior cultivar usage and time-consuming introgression through backcrossing to the preferred variety. Overcoming these limitations will greatly facilitate the development of disease, insect, and abiotic stress tolerant crops. One such avenue for rapid crop improvement is the development of viral systems to deliver CRISPR/Cas-based genome editing technology to plants to generate targeted beneficial mutations. Viral delivery of genomic editing constructs can theoretically be applied to span the entire host range of the virus utilized, circumventing the challenges associated with traditional transformation and breeding techniques. Here we explore the types of viruses that have been optimized for CRISPR/Cas9 delivery, the phenotypic outcomes achieved in recent studies, and discuss the future potential of this rapidly advancing technology.
Nutrient availability is a determining factor for crop yield and quality. While fertilization is a major approach for improving plant nutrition, its efficacy can be limited and the production and application of fertilizers frequently bring problems to the environment. A large number of soil microbes are capable of enhancing plant nutrient acquisition and thereby offer environmentally benign solutions to meet the requirements of plant nutrition. Herein we provide summations of how beneficial microbes enhance plant acquisition of macronutrients and micronutrients. We also review recent studies on nutrition-dependent plant-microbe interactions, which highlight the plant’s initiative in establishing or deterring the plant-microbe association. By dissecting complex signaling interactions between microbes within the root microbiome, a greater understanding of microbe-enhanced plant nutrition under specific biotic and abiotic stresses will be possible.
Nitrogen is one of the most important nutrient for plant growth and development; it is strongly associated with a variety of abiotic stress responses. As sessile organisms, plants have evolved to develop efficient strategies to manage N to support growth when exposed to a diverse range of stressors. This review summarizes the recent progress in the field of plant nitrate (NO3 -) and ammonium (NH4 +) uptake, which are the two major forms of N that are absorbed by plants. We explore the intricate relationship between NO3 -/NH4 + and abiotic stress responses in plants, focusing on stresses from nutrient deficiencies, unfavorable pH, ions, and drought. Although many molecular details remain unclear, research has revealed a number of core signaling regulators that are associated with N-mediated abiotic stress responses. An in-depth understanding and exploration of the molecular processes that underpin the interactions between N and abiotic stresses is useful in the design of effective strategies to improve crop growth, development, and productivity.
While conventional chemical fungicides directly eliminate pathogens, plant immunity inducers activate or prime plant immunity. In recent years, considerable progress has been made in understanding the mechanisms of immune regulation in plants. The development and application of plant immunity inducers based on the principles of plant immunity represent a new field in plant protection research. In this review, we describe the mechanisms of plant immunity inducers in terms of plant immune system activation, summarize the various classes of reported plant immunity inducers (proteins, oligosaccharides, chemicals, and lipids), and review methods for the identification or synthesis of plant immunity inducers. The current situation, new strategies, and future prospects in the development and application of plant immunity inducers are also discussed.
Mitogen-activated protein kinase (MAPK) cascades are activated by external stimuli and convert signals to cellular changes. Individual MAPKs have been characterized in a number of plant pathogenic fungi for their roles in pathogenesis and responses to biotic or abiotic stresses. However, mutants deleted of all the MAPK genes have not been reported in filamentous fungi. To determine the MAPK-less effects in a fungal pathogen, in this study we generated and characterized mutants deleted of all three MAPK genes in the wheat scab fungus Fusarium graminearum. The Gpmk1 mgv1 Fghog1 triple mutants had severe growth defects and was non-pathogenic. It was defective in infection cushion formation and DON production. Conidiation was reduced in the triple mutant, which often produced elongated conidia with more septa than the wild-type conidia. The triple mutant was blocked in sexual reproduction due to the loss of female fertility. Lack of any MAPKs resulted in an increased sensitivity to various abiotic stress including cell wall, osmotic, oxidative stresses, and phytoalexins, which are likely related to the defects of the triple mutant in environmental adaptation and plant infection. The triple mutant also had increased sensitivity to the biocontrol bacterium Bacillus velezensis and fungus Clonostachys rosea. In co-incubation assays with B. velezensis, the Gpmk1 mgv1 Fghog1 mutant had more severe growth limitation than the wild type and was defective in conidium germination and germ tube growth. In confrontation assays, the triple mutant was defective in defending against mycoparasitic activities of C. rosea and the latter could grow over the mutant but not wild-type F. graminearum. RNA-seq and metabolomics analyses showed that the MAPK triple mutant was altered in the expression of many ATP-binding cassette (ABC) and major facilitator superfamily (MFS) transporter genes and the accumulation of metabolites related to arachidonic acid, linoleic acid, and alpha-linolenic acid metabolisms. Overall, as the first study on mutants deleted of all three MAPKs in fungal pathogens, our results showed that although MAPKs are not essential for growth and asexual reproduction, the Gpmk1 mgv1 Fghog1 triple mutant was blocked in plant infection and sexual reproductions. It also had severe defects in responses to various abiotic stresses and bacterial- or fungal-fungal interactions.
Conserved effectors produced by phytopathogens play critical roles in plant-microbe interactions. NIS1-like proteins represent a newly identified family of effectors distributed in multiple fungal species. However, their biological functions in a majority of pathogenic fungi remain largely elusive and require further investigation. In this study, we characterized two NIS1-like proteins VmNIS1 and VmNIS2 from Valsa mali, the causal agent of apple Valsa canker. Both of these two proteins were predicted to be secreted. Using agroinfiltration, we found that VmNIS1 induced intense cell death, whereas VmNIS2 suppressed INF1 elicitin-triggered cell death in Nicotiana benthamiana. Treatment of N. benthamiana with VmNIS1 recombinant protein produced by Escherichia coli activated a series of immune responses and enhanced plant disease resistance against Phytophthora capsici. In contrast, VmNIS2 suppressed plant immune responses and promoted P. capsici infection when transiently expressed in N. benthamiana. Both VmNIS1 and VmNIS2 were shown to be highly induced at late stage of V. mali infection. By individually knocking out of these two genes in V. mali, however, only VmNIS2 was shown to be required for pathogen virulence as well as tolerance to oxidative stress. Notably, we further showed that C-terminal extension of VmNIS1 was essential for plant recognition and VmNIS2 may escape plant detection via sequence truncation. Our data collectively indicate that VmNIS1 and VmNIS2 play distinct roles in plant recognition and pathogen virulence, which provided new insights into the function of NIS1-like proteins in plant-microbe interactions.
Species of wild rice (Oryza spp.) possess a wide range of stress tolerance traits that can be potentially utilized in breeding climate-resilient cultivated rice cultivars (Oryza sativa) thereby aiding global food security. In this study, we conducted a greenhouse trial to evaluate the salinity tolerance of six wild rice species, one cultivated rice cultivar (IR64) and one landrace (Pokkali) using a range of electrophysiological, imaging, and whole-plant physiological techniques. Three wild species (O. latifolia, O. officinalis and O. coarctata) were found to possess superior salinity stress tolerance. The underlying mechanisms, however, were strikingly different. Na+ accumulation in leaves of O. latifolia, O. officinalis and O. coarctata were significantly higher than the tolerant landrace, Pokkali. Na+ accumulation in mesophyll cells was only observed in O. coarctata, suggesting that O. officinalis and O. latifolia avoid Na+ accumulation in mesophyll by allocating Na+ to other parts of the leaf. The finding also suggests that O. coarctata might be able to employ Na+ as osmolyte without affecting its growth. Further study of Na+ allocation in leaves will be helpful to understand the mechanisms of Na+ accumulation in these species. In addition, O. coarctata showed Proto Kranz-like leaf anatomy (enlarged bundle sheath cells and lower numbers of mesophyll cells), and higher expression of C4-related genes (e.g., NADPME, PPDK) and was a clear outlier with respect to salinity tolerance among the studied wild and cultivated Oryza species. The unique phylogenetic relationship of O. coarctata with C4 grasses suggests the potential of this species for breeding rice with high photosynthetic rate under salinity stress in the future.
Arsenic is a metalloid toxic to plants, animals and human beings. Small ubiquitin-like modifier (SUMO) conjugation is involved in many biological processes in plants. However, the role of SUMOylation in regulating plant arsenic response is still unclear. In this study, we found that dysfunction of SUMO E3 ligase SIZ1 improves arsenite resistance in Arabidopsis. Overexpression of the dominant-negative SUMO E2 variant resembled the arsenite-resistant phenotype of siz1 mutant, indicating that SUMOylation plays a negative role in plant arsenite detoxification. The siz1 mutant accumulated more glutathione (GSH) than the wild type under arsenite stress, and the arsenite-resistant phenotype of siz1 was depressed by inhibiting GSH biosynthesis. The transcript levels of the genes in the GSH biosynthetic pathway were increased in the siz1 mutant comparing with the wild type in response to arsenite treatment. Taken together, our findings revealed a novel function of SIZ1 in modulating plant arsenite response through regulating the GSH-dependent detoxification.
Both viruses and host cells compete for intracellular polyamines for efficient propagation. Currently, how the key polyamine-metabolizing enzymes, including ornithine decarboxylase 1 (ODC1) and its antizyme 1 (OAZ1), are activated to co-ordinate viral propagation and polyamine biosynthesis remains unknown. Here, we report that the matrix protein of rice stripe mosaic virus (RSMV), a cytorhabdovirus, directly hijacks OAZ1 to ensure the proper assembly of rigid bacilliform non-enveloped virions in leafhopper vector. Viral matrix protein effectively competes with ODC1 to bind to OAZ1, and thus, the ability of OAZ1 to target and mediate the degradation of ODC1 is significantly inhibited during viral propagation, which finally promotes polyamines production. Thus, OAZ1 and ODC1 are activated to synergistically promote viral persistent propagation and polyamine biosynthesis in viruliferous vectors. Our data suggest that it is a novel mechanism for rhabdovirus to exploit OAZ1 for facilitating viral assembly.
Temperature, water, and light are three abiotic stress factors that have major influences on plant growth, development, and reproduction. Plants can be primed by a prior mild stress to enhance their resistance to future stress. We used an untargeted metabolomics approach to examine Arabidopsis thaliana 11-day-old seedling’s abiotic stress responses including heat (with and without priming), cold (with and without priming), water-deficit and high-light before and after a 2-day-recovery period. Analysis of the physiological phenotypes showed that seedlings with stress treatment resulted in a reduction in fresh weight, hypocotyl and root length but remained viable. Several stress responsive metabolites were identified, confirmed with reference standards, quantified, and clustered. We identified shared and specific stress signatures for cold, heat, water-deficit, and high-light treatments. Central metabolism including amino acid metabolism, sugar metabolism, glycolysis, TCA cycle, GABA shunt, glutathione metabolism, purine metabolism, and urea cycle were found to undergo changes that are fundamentally different, although some shared commonalities in response to different treatments. Large increases in cysteine abundance and decreases in reduced glutathione were observed following multiple stress treatments highlighting the importance of oxidative stress as a general phenomenon in abiotic stress. Large fold increases in low-turnover amino acids and maltose demonstrate the critical role of protein and starch autolysis in early abiotic stress responses.
Plant innate immunity begins with the recognition of pathogens by plasma membrane localized pattern-recognition receptors (PRRs) and intracellular nucleotide-binding domain leucine-rich repeat containing receptors (NLRs), which lead to pattern-triggered immunity (PTI) and effector-triggered immunity (ETI), respectively. For a long time, PTI and ETI have been regarded as two independent processes although they share multiple components and signal outputs. Increasing evidence shows an intimate link between PTI and ETI. PTI and ETI mutually potentiate each other, and this is essential for robust disease resistance during pathogen infection. An ancient class of NLRs called RNLs, so named because they carry a Resistance to Powdery Mildew 8 (RPW8)-like coiled-coil (CC) domain in the N terminus, has emerged as a key node connecting PTI and ETI. RNLs not only act as helper NLRs that signal downstream of sensor NLRs, they also directly mediate PTI signaling by associating with PRR complexes. Here, we focus on Activated Disease Resistance 1 (ADR1), a subclass of RNLs, and discuss its role and mechanism in plant immunity.
Maintenance of root elongation is beneficial for the growth and survival of plants under salt stress, but currently the cellular components involved in the regulation of root growth under high salinity are not fully understood. In this study, we identified an Arabidopsis mutant, rres1, which exhibited reduced root elongation under treatment of a variety of salts, including NaCl, NaNO3, KCl, and KNO3. RRES1 encodes a novel mitochondrial protein and its molecular function is still unknown. Under salt stress, the root meristem length was shorter in the rres1 mutant compared to the wild type, which was correlated with a reduced auxin accumulation in the mutant. Reactive oxygen species (ROS), as important signals that regulate root elongation, were accumulated to higher levels in the rres1 mutant than the wild type after salt treatment. Measurement of monosaccharides in the cell wall showed that arabinose and xylose contents were decreased in the rres1 mutant under salt stress, and application of boric acid, which is required for the crosslinking of pectic polysaccharide rhamnogalacturonan-II (RG-II), largely rescued the root growth arrest of the rres1 mutant, suggesting that RRES1 participates in the maintenance of cell wall integrity under salt stress. GUS staining assay indicated that the RRES1 gene was expressed in leaves and weakly in root tip under normal conditions, but its expression was dramatically increased in leaves and roots after salt treatment. Together, our study reveals a novel mitochondrial protein that regulates root elongation under salt stress via the modulation of cell wall integrity, auxin accumulation, and ROS homeostasis.
The circadian clock, a time-keeping mechanism, drives nearly 24-h self-sustaining rhythms at the physiological, cellular, and molecular levels, keeping them synchronized with the cyclic changes of environmental signals. The plant clock is sensitive to external and internal stress signals that act as timing cues to influence the circadian rhythms through input pathways of the circadian clock system. In order to cope with environmental stresses, many core oscillators are involved in defense while maintaining daily growth in various ways. Recent studies have shown that a hierarchical multi-oscillator network orchestrates the defense through rhythmic accumulation of gene transcripts, alternative splicing of mRNA precursors, modification and turnover of proteins, subcellular localization, stimuli-induced phase separation, and long-distance transport of proteins. This review summarizes the essential role of circadian core oscillators in response to stresses in Arabidopsis thaliana and crops, including daily and seasonal abiotic stresses (low or high temperature, drought, high salinity, and nutrition deficiency) and biotic stresses (pathogens and herbivorous insects). By integrating time-keeping mechanisms, circadian rhythms and stress resistance, we provide a temporal perspective for scientists to better understand plant environmental adaptation and breed high-quality crop germplasm for agricultural production.
Phosphorus (P) is obtained by plants as phosphate (Pi) from the soil and low Pi levels affects plant growth and development. Adaptation to low Pi condition entails sensing internal and external Pi levels and translating those signals to molecular and morphophysiological changes in the plant. In this review, we present findings related to local and systemin Pi sensing with focus the molecular mechanisms behind root system architectural changes and the impact of hormones and epigenetic mechanisms affecting those changes. We also present some of the recent advances in the Pi sensing and signaling mechanisms focusing on inositol pyrophosphate InsP8 and its interaction with SPX domain proteins to regulate the activity of the central regulator of the Pi starvation response, PHR.
STOP1 (sensitive to proton rhizotoxicity1) is a master transcription factor that governs the expression of a set of regulatory and structural genes involved in resistance to aluminum and low pH (i.e., proton) stresses in Arabidopsis. However, the mechanisms and regulatory networks underlying STOP1-mediated resistance to proton stresses are largely unclear. Here, we report that low-pH stresses severely inhibited root growth of the stop1 plants by suppressing root meristem activities. Interestingly, the stop1 plants were less sensitive to exogenous cytokinins at normal and low pHs than the wild type. Significantly, low concentrations of cytokinins promoted root growth of the stop1 mutant under low-pH stresses. Moreover, lateral and adventitious root formation was stimulated in stop1 and by low-pH stresses but suppressed by cytokinins. Further studies of the expression patterns of a cytokinin signaling reporter suggest that both the loss-of-function mutation of STOP1 and low-pH stresses suppressed cytokinin signaling outputs in the root. Furthermore, the expression of critical genes involved in cytokinin biosynthesis, biodegradation, and signaling is altered in the stop1 mutant in response to low-pH stresses. In conclusion, our results reveal a complex network of resistance to low-pH stresses, which involves coordinated actions of STOP1, cytokinins, and an additional low-pH-resistant mechanism for controlling root meristem activities and root growth upon proton stresses.
Tomato is an important vegetable crop and fluctuating available soil phosphate (Pi) level elicits several morpho-physiological responses driven by underlying molecular responses. Therefore, understanding these molecular responses at the gene and isoform levels has become critical in the quest for developing crops with improved Pi use efficiency. A quantitative time-series RNA-seq analysis was performed to decipher the global transcriptomic changes that accompany Pi starvation in tomato. Apart from changes in the expression levels of genes, there were also alterations in the expression of alternatively-spliced transcripts. Physiological responses such as anthocyanin accumulation, reactive oxygen species generation and cell death are obvious 7 days after Pi deprivation accompanied with the maximum amount of transcriptional change in the genome making it an important stage for in-depth study while studying Pi stress responses (PSR). Our study demonstrates that transcriptomic changes under Pi deficiency are dynamic and complex in tomato. Overall, our study dwells on the dynamism of the transcriptome in eliciting a response to adapt to low Pi stress and lays it bare. Findings from this study will prove to be an invaluable resource for researchers using tomato as a model for understanding nutrient deficiency.
Tomato yellow leaf curl virus (TYLCV) is known to encode 6 canonical viral proteins. Our recent study revealed that TYLCV also encodes some additional small proteins with potential virulence functions. The fifth ORF of TYLCV in the complementary sense, which we name C5, is evolutionarily conserved, but little is known about its expression and function during viral infection. Here, we confirmed the expression of the TYLCV C5 by analyzing the promoter activity of its upstream sequences and by detecting the C5 protein in infected cells by using a specific custom-made antibody. Ectopic expression of C5 using a potato virus X (PVX) vector resulted in severe mosaic symptoms and higher virus accumulation levels followed by a burst of reactive oxygen species (ROS) in Nicotiana benthamiana plants. C5 was able to effectively suppress local and systemic post-transcriptional gene silencing (PTGS) induced by single-stranded GFP but not double-stranded GFP, and reversed the transcriptional gene silencing (TGS) of GFP. Furthermore, the mutation of C5 in TYLCV inhibited viral replication and the development of disease symptoms in infected plants. Transgenic overexpression of C5 could complement the virulence of a TYLCV infectious clone encoding a dysfunctional C5. Collectively, this study reveals that TYLCV C5 is a pathogenicity determinant and RNA silencing suppressor, hence expanding our knowledge of the functional repertoire of the TYLCV proteome.
Common in Fungal Extracellular Membrane (CFEM) domain proteins are considered to be unique to fungi and closely related to pathogenicity. However, the Puccinia striiformis f. sp. tritici (Pst) effector containing the CFEM domain has not been reported. Here, we obtained an effector, PstCFEM1, containing a functional N-terminal signal peptide sequence and the CFEM domain from Pst race CYR31. qRT-PCR assay indicated that the transcript levels of PstCFEM1 were highly induced during the early stages of infection. Overexpression of PstCFEM1 suppressed Pst322 (an elicitor-like protein of Pst)-trigged cell death, reactive oxygen species (ROS) accumulation and callose deposition. Host-induced gene silencing (HIGS) experiments showed that knockdown of PstCFEM1 decreased the virulence of Pst, while ROS accumulation in silenced plants increased near the infection site. In addition, wheat containing the PstCFEM1-silenced construct increased resistance to multiple races of Pst. Our data suggest that PstCFEM1 suppresses wheat defense by inhibiting ROS accumulation and contributes to increased virulence of Pst.
Bacteria and fungi are dominant members of environmental microbiomes. Various bacterial-fungal interactions (BFIs) and their mutual regulation are important factors for ecosystem functioning and health. Such interactions can be highly dynamic, and often require spatiotemporally resolved assessments to understand the interplay which ranges from antagonism to mutualism. Many of these interactions are still poorly understood, especially in terms of the underlying chemical and molecular interplay, which is crucial for inter-kingdom communication and interference. BFIs are highly relevant under agricultural settings; they can be determinative for crop health. Advancing our knowledge related to mechanisms underpinning the interactions between bacteria and fungi will provide an extended basis for biological control of pests and pathogens in agriculture. Moreover, it will facilitate a better understanding of complex microbial community networks that commonly occur in nature. This will allow us to determine factors that are crucial for community assembly under different environmental conditions and pave the way for constructing synthetic communities for various biotechnological applications. Here, we summarize the current advances in the field of BFIs with an emphasis on agriculture.
Low molecular weight protein tyrosine phosphatase (LWM-PTP), also known as acid phosphatase, is a highly conserved tyrosine phosphatase in living organisms. However, the function of LWM-PTP homolog has not been reported yet in plants. Here, we revealed a homolog of acid phosphatase, APH, in Arabidopsis plants, is a functional protein tyrosine phosphatase. The aph mutants are hyposensitive to ABA in post-germination growth. We performed an anti-phosphotyrosine antibody-based quantitative phosphoproteomics in wild-type and aph mutant and identified hundreds of putative targets of APH, including multiple splicing factors and other transcriptional regulators. Consistently, RNA-seq analysis revealed that the expression of ABA-highly-responsive genes is suppressed in aph mutants. Thus, APH regulates the ABA-responsive gene expressions by regulating the tyrosine phosphorylation of multiple splicing factors and other post-transcriptional regulators. We also revealed that Tyr383 in RAF9, a member of B2 and B3 RAF kinases that phosphorylate and activate SnRK2s in the ABA signaling pathway, is a direct target site of APH. Phosphorylation of Tyr383 is essential for RAF9 activity. Our results uncovered a crucial function of APH in ABA-induced tyrosine phosphorylation in Arabidopsis.
Plant vascular pathogens are one kind of destructive pathogens in agricultural production. However, mechanisms behind the vascular pathogen-recognition and the subsequent defense responses of plants are not well known. A recent pioneering study on plant vascular immunity discovered a conserved MKP1-MPK-MYB signaling cascade that activates lignin biosynthesis in vascular tissues to confer vascular resistance in both monocot rice and the dicot Arabidopsis. The breakthrough provides a novel view on plant immunity to vascular pathogens and offers a potential strategy for the future breeding of disease-resistant crops.
As sessile organisms, plants have to cope with environmental change and numerous biotic and abiotic stress. Upon perceiving environmental cues and stress signals using different types of receptors, plant cells initiate immediate and complicated signaling to regulate cellular processes and respond to stress. Receptor-like cytoplasmic kinases (RLCKs) transduce signals from receptors to cellular components and play roles in diverse biological processes. Recent studies have revealed the hubbing roles of RLCKs in plant responses to biotic stress. Emerging evidence indicates the important regulatory roles of RLCKs in plant responses to abiotic stress, growth, and development. As a pivot of cellular signaling, the activity and stability of RLCKs are dynamically and tightly controlled. Here, we summarize the current understanding of how RLCKs regulate plant responses to biotic and abiotic stress.
Plants are sessile organisms that evolve with a flexible signal transduction system in order to rapidly respond to environmental changes. Drought, a common abiotic stress, affects multiple plant developmental processes especially growth. In response to drought stress, an intricate hierarchical regulatory network is established in plant to survive from the extreme environment. The transcriptional regulation carried out by transcription factors (TFs) is the most important step for the establishment of the network. In this review, we summarized almost all the TFs that have been reported to participate in drought tolerance (DT) in plant. Totally 466 TFs from 86 plant species that mostly belong to 11 families are collected here. This demonstrates that TFs in these 11 families are the main transcriptional regulators of plant DT. The regulatory network is built by direct protein-protein interaction or mutual regulation of TFs. TFs receive upstream signals possibly via post-transcriptional regulation and output signals to downstream targets via direct binding to their promoters to regulate gene expression.
Rice (Oryza sativa L.) is a staple crop that feeds over half the world’s population. High temperature stress is a great threaten to sustainable agriculture and leads to yield loss and impaired grain quality in major crops. Rice is sensitive to heat stress at almost all the growth stages and the molecular mechanisms underlying responses to heat stress in rice is emerging. Through quantitative trait locus (QTL) mapping, a recent study conducted by Zhang et al. shows that one genetic locus Thermo-tolerance 3 (TT3) contains two genes that are required for thermotolerance in rice. The TT3.1–TT3.2 genetic module in rice links the plasma membrane to chloroplasts to protect chloroplasts from heat stress damage and increases grain yield under heat stress conditions. This breakthrough provides a promising strategy for future breeding of high temperature resilient crops.
The deficient agricultural water caused by water shortage is a crucial limiting factor of horticultural production. Among many agricultural water-saving technologies, regulated deficit irrigation (RDI) has been proven to be one of the effective technologies to improve water use efficiency and reduce water waste on the premise of maintaining the quality of agricultural products. RDI was first reported more than 40 years ago, although it has been applied in some areas, little is known about understanding of the implementation method, scope of application and detailed mechanism of RDI, resulting in the failure to achieve the effect that RDI should have. This review refers to the research on RDI in different crops published in recent years, summarizes the definition, equipment condition, function, theory illumination, plant response and application in different crops of RDI, and looks forward to its prospect. We expect that this review will provide valuable guidance for researchers and producers concerned, and support the promotion of RDI in more horticultural crops.
DNA methylation is an important epigenetic marker for the suppression of transposable elements (TEs) and the regulation of plant immunity. However, little is known how RNA viruses counter defense such antiviral machinery. In this study, the change of DNA methylation in turnip mosaic virus (TuMV)-infected cells was analyzed by whole genome bisulfite sequencing. Results showed that the total number of methylated sites of CHH and CHG increased in TuMV-infected cells, the majority of differentially methylated regions (DMRs) in the CHH and CHG contexts were associated with hypermethylation. Gene expression analysis showed that the expression of two methylases (DRM2 and CMT3) and three demethylases (ROS3, DML2, DML3) was significantly increased and decreased in TuMV-infected cells, respectively. Pathogenicity tests showed that the enhanced resistance to TuMV of the loss-of-function mutant of DRM2 is associated with unregulated expression of several defense-related genes. Finally, we found TuMV-encoded NIb, the viral RNA-dependent RNA polymerase, was able to induce the expression of DRM2. In conclusion, this study discovered that TuMV can modulate host DNA methylation by regulating the expression of DRM2 to promote virus infection.
Plant intracellular nucleotide-binding leucine-rich repeat (NLR) receptors with an N-terminal Toll/Interleukin-1 receptor (TIR) domain detect pathogen effectors to produce TIR-catalyzed signaling molecules for activation of plant immunity. Plant immune signaling by TIR-containing NLR (TNL) proteins converges on Enhanced Disease Susceptibility 1 (EDS1) and its direct partners Phytoalexin Deficient 4 (PAD4) or Senescence-Associated Gene 101 (SAG101). TNL signaling also require helper NLRs N requirement gene 1 (NRG1) and activated disease resistance 1 (ADR1). In two recent remarkable papers published in Science, the authors show that the TIR-containing proteins catalyze and produce two types of signaling molecules, ADPr-ATP/diADPR and pRib-AMP/ADP. Importantly, they demonstrate that EDS1-SAG101 and EDS1-PAD4 modules are the receptor complexes for ADPr-ATP/diADPRp and Rib-AMP/ADP, respectively, which allosterically promote EDS1-SAG101 interaction with NRG1 and EDS1-PAD4 interaction with ADR1. Thus, two different small molecules catalyzed by TIR-containing proteins selectively activate the downstream two distinct branches of EDS1-mediated immune signalings. These breakthrough studies significantly advance our understanding of TNL downstream signaling pathway.
Two-pore cation channel, TPC1, is ubiquitous in the vacuolar membrane of terrestrial plants and mediates the long distance signaling upon biotic and abiotic stresses. It possesses a wide pore, which transports small mono- and divalent cations. K+ is transported more than 10-fold faster than Ca2+, which binds with a higher affinity within the pore. Key pore residues, responsible for Ca2+ binding, have been recently identified. There is also a substantial progress in the mechanistic and structural understanding of the plant TPC1 gating by membrane voltage and cytosolic and luminal Ca2+. Collectively, these gating factors at resting conditions strongly reduce the potentially lethal Ca2+ leak from the vacuole. Such tight control is impressive, bearing in mind high unitary conductance of the TPC1 and its abundance, with thousands of active channel copies per vacuole. But it remains a mystery how this high threshold is overcome upon signaling, and what type of signal is emitted by TPC1, whether it is Ca2+ or electrical one, or a transduction via protein conformational change, independent on ion conductance. Here we discuss non-exclusive scenarios for the TPC1 integration into Ca2+, ROS and electrical signaling.
Rice sheath blight pathogen, Rhizoctonia solani, produces numerous sclerotia to overwinter. As a rich source of nutrients in the soil, sclerotia may lead to the change of soil microbiota. For this purpose, we amended the sclerotia of R. solani in soil and analyzed the changes in bacterial microbiota within the soil at different time points. At the phyla level, Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chloroflexi and Firmicutes showed varied abundance in the amended soil samples compared to those in the control. An increased abundance of ammonia-oxidizing bacterium (AOB) Nitrosospira and Nitrite oxidizing bacteria (NOB) i.e., Nitrospira was observed, where the latter is reportedly involved in the nitrifier denitrification. Moreover, Thiobacillus, Gemmatimonas, Anaeromyxobacter and Geobacter, the vital players in denitrification, N2O reduction and reductive nitrogen transformation, respectively, depicted enhanced abundance in R. solani sclerotia-amended samples. Furthermore, asymbiotic nitrogen-fixing bacteria, notably, Azotobacter as well as Microvirga and Phenylobacterium with nitrogen-fixing potential also enriched in the amended samples compared to the control. Plant growth promoting bacteria, such as Kribbella, Chitinophaga and Flavisolibacter also enriched in the sclerotia-amended soil. As per our knowledge, this study is of its kind where pathogenic fungal sclerotia activated microbes with a potential role in N transformation and provided clues about the ecological functions of R. solani sclerotia on the stimulation of bacterial genera involved in different processes of N-cycle within the soil in the absence of host plants.
As sessile organisms, plants encounter diverse invasions from pathogens including viruses. To survive and thrive, plants have evolved multilayered defense mechanisms to combat virus infection. RNAi, also known as RNA silencing, is an across-kingdom innate immunity and gene regulatory machinery. Molecular framework and crucial roles of RNAi in antiviral defense have been well-characterized. However, it is largely unknown that how RNAi is transcriptionally regulated to initiate, maintain and enhance cellular silencing under normal or stress conditions. Recently, insights into the transcriptional and post-transcriptional regulation of RNAi-related genes in different physiological processes have been emerging. In this review, we integrate these new findings to provide updated views on how plants modulate RNAi machinery at the (post-) transcriptional level to respond to virus infection.
Alternative splicing (AS) regulation of pre-mRNA has been proven to be one of the fundamental layers of plant immune system. How pathogens disrupt plant AS process to suppress plant immunity by secreted effectors remain poorly understood. In the recent study, Gui et al. revealed that a previously identified effector PSR1 of Phytophthora interferes with host RNA splicing machinery to modulate small RNA biogenesis, leading to compromised plant immunity. The study provided a novel insight into the importance of AS process during pathogen-host interactions.
Plants have to cope with the surrounding changing environmental stimuli to optimize their physiological and developmental response throughout their entire life cycle. Light and temperature are two critical environmental cues that fluctuate greatly during day-night cycles and seasonal changes. These two external signals coordinately control the plant growth and development. Distinct spectrum of light signals are perceived by a group of wavelength-specific photoreceptors in plants. PIFs and COP1-HY5 are two predominant signaling hubs that control the expression of a large number of light-responsive genes and subsequent light-mediated development in plants. In parallel, plants also transmit low or warm temperature signals to these two regulatory modules that precisely modulate the responsiveness of low or warm temperatures. The core component of circadian clock ELF3 integrates signals from light and warm temperatures to regulate physiological and developmental processes in plants. In this review, we summarize and discuss recent advances and progresses on PIFs-, COP1-HY5- and ELF3-mediated light, low or warm temperature signaling, and highlight emerging insights regarding the interactions between light and low or warm temperature signal transduction pathways in the control of plant growth.
Plants face a constantly changing environment, requiring fine tuning of their growth and development. Plants have therefore developed numerous mechanisms to cope with environmental stress conditions. One striking example is root response to water deficit. Upon drought (which causes osmotic stress to cells), plants can among other responses alter locally their root system architecture (hydropatterning) or orientate their root growth to optimize water uptake (hydrotropism). They can also modify their hydraulic properties, metabolism and development coordinately at the whole root and plant levels. Upstream of these developmental and physiological changes, plant roots must perceive and transduce signals for water availability. Here, we review current knowledge on plant osmotic perception and discuss how long distance signaling can play a role in signal integration, leading to the great phenotypic plasticity of roots and plant development.
Global food production is at risk from many abiotic and biotic stresses and can be affected by multiple stresses simultaneously. Virus diseases damage cultivated plants and decrease the marketable quality of produce. Importantly, the progression of virus diseases is strongly affected by changing climate conditions. Among climate-changing variables, temperature increase is viewed as an important factor that affects virus epidemics, which may in turn require more efficient disease management. In this review, we discuss the effect of elevated temperature on virus epidemics at both macro- and micro-climatic levels. This includes the temperature effects on virus spread both within and between host plants. Furthermore, we focus on the involvement of molecular mechanisms associated with temperature effects on plant defence to viruses in both susceptible and resistant plants. Considering various mechanisms proposed in different pathosystems, we also offer a view of the possible opportunities provided by RNA -based technologies for virus control at elevated temperatures. Recently, the potential of these technologies for topical field applications has been strengthened through a combination of genetically modified (GM)-free delivery nanoplatforms. This approach represents a promising and important climate-resilient substitute to conventional strategies for managing plant virus diseases under global warming scenarios. In this context, we discuss the knowledge gaps in the research of temperature effects on plant-virus interactions and limitations of RNA-based emerging technologies, which should be addressed in future studies.
The phytohormone abscisic acid (ABA) plays important roles in plant growth, development and adaptative responses to abiotic stresses. SNF1-related protein kinase 2s (SnRK2) are key components that activate the ABA core signaling pathway. NUCLEAR PORE ANCHOR (NUA) is a component of the nuclear pore complex (NPC) that involves in deSUMOylation through physically interacting with the EARLY IN SHORT DAYS 4 (ESD4) SUMO protease. However, it is not clear how NUA functions with SnRK2 and ESD4 to regulate ABA signaling. In our study, we found that nua loss-of-function mutants exhibited pleiotropic ABA-hypersensitive phenotype. We also found that ABA-responsive genes remarkably up-regulated in nua by exogenous ABA. The nua snrk2.2 snrk2.3 triple mutant and nua abi5 double mutant partially rescued the ABA-hypersensitive phenotype of nua, thereby suggesting that NUA is epistatic to SnRK2s. Additionally, we observed that esd4-3 mutant was also ABA-hypersensitive. NUA and ESD4 were further demonstrated to physically interact with SnRK2s and negatively regulate ABA signaling by reducing SnRK2s stability. Taken together, our findings uncover a new regulatory mechanism that can modulate ABA signaling.
Salt stress causes osmotic stress, ion toxicity and oxidative stress, inducing the accumulation of abscisic acid (ABA) and excessive reactive oxygen species (ROS) production, which further damage cell structure and inhibit the development of roots in plants. Previous study showed that vitamin B6 (VB6) plays a role in plant responses to salt stress, however, the regulatory relationship between ROS, VB6 and ABA under salt stress remains unclear yet in plants. In our study, we found that salt stress-induced ABA accumulation requires ROS production, in addition, salt stress also promoted VB6 (including pyridoxamine (PM), pyridoxal (PL), pyridoxine (PN), and pyridoxal 5′-phosphate (PLP)) accumulation, which involved in ROS scavenging and ABA biosynthesis. Furthermore, VB6-deficient maize mutant small kernel2 (smk2) heterozygous is more susceptible to salt stress, and which failed to scavenge excessive ROS effectively or induce ABA accumulation in maize root under salt stress, interestingly, which can be restored by exogenous PN and PLP, respectively. According to these results, we proposed that PN and PLP play an essential role in balancing ROS and ABA levels under salt stress, respectively, it laid a foundation for VB6 to be better applied in crop salt resistance than ABA.
Wheat is one of the most important cereal crops, and it is essential for worldwide food security. However, wheat production is threatened by various diseases, including wheat stripe rust caused by the fungus Puccinia striiformis f. sp. tritici (Pst). The development of plant resistance against disease is usually challenged by potential reduction in crop yield due to the enhancement of plant immunity. In a recent article, Wang et al. found that TaPsIPK1 is a susceptibility gene targeted by rust effectors. Editing of TaPsIPK1 increases resistance to stripe rust without any developmental effects or yield penalty, providing an exceptional resource for developing disease resistance in wheat.
The mitotic exit network (MEN) pathway is a vital kinase cascade regulating the timely and correct progress of cell division. In the rice blast fungus Magnaporthe oryzae, the MEN pathway, consisting of conserved protein kinases MoSep1 and MoMob1-MoDbf2, is important in the development and pathogenicity of the fungus. We found that deletion of MoSEP1 affects the phosphorylation of MoMob1, but not MoDbf2, in contrast to what was found in the buddy yeast Saccharomyces cerevisiae, and verified this finding by in vitro phosphorylation assay and mass spectrometry (MS) analysis. We also found that S43 residue is the critical phosphor-site of MoMob1 by MoSep1, and proved that MoSep1-dependent MoMob1 phosphorylation is essential for cell division during the development of M. oryzae. We further provided evidence demonstrating that MoSep1 phosphorylates MoMob1 to maintain the cell cycle during vegetative growth and infection. Taken together, our results revealed that the MEN pathway has both distinct and conservative functions in regulating the cell cycle during the development and pathogenesis of M. oryzae.
The plant vacuole plays a fundamental role in cell homeostasis. The successful application of patch-clamp technique on isolated vacuoles allows the determination of the functional characteristics of tonoplast ion channels and transporters. The parallel use of a sensor-based fluorescence approach capable of detecting changes in calcium and proton concentrations opens up new possibilities for investigation. In excised patch, the presence of fura-2 in the vacuolar solution reveals the direct permeation of calcium in plant TPC channels. In whole-vacuole, the activity of non-electrogenic NHX potassium proton antiporters can be measured by using the proton sensitive dye BCECF loaded in the vacuolar lumen by the patch pipette. Both vacuolar NHXs and CLCa (chloride/nitrate antiporter) are inhibited by the phosphoinositide PI(3,5)P2, suggesting a coordinated role of these proteins in salt accumulation. Increased knowledge in the molecular mechanisms of vacuolar ion channels and transporters has the potential to improve our understanding on how plants cope with a rapidly changing environment.
This brief article highlights the results of Fu et al. (Proc Natl Acad Sci USA 119:e2204574119, 2022), who recently found that manganese (Mn) deficiency triggers long-lasting multicellular Ca2+ oscillations in the elongation zone (EZ) of Arabidopsis roots and revealed a Ca2+-CPK21/23-NRAMP1 axis as an important mechanism for plant tolerance and adaptation to low Mn.
The sucrose non-fermenting 1 (SNF1)-related protein kinase 2 (SnRK2) family members have been discovered to regulate abiotic stress response via the abscisic acid (ABA)-independent and dependent signaling pathways. SnRK2.6, also known as Open Stomata 1 (OST1), is a serine/threonine protein kinase that plays critical roles in linking ABA receptor complexes and downstream components such as transcription factors and anion channels to regulate stress response. Asides from its well-known regulatory roles in stomatal movement and cold stress response, OST1 has also been demonstrated recently to modulate major developmental roles of flowering and growth in plants. In this review, we will discuss about the various roles of OST1 as well as the ‘doors’ that OST1 can ‘open’ to help plants perform stress adaptation. Therefore, we will address how OST1 can regulate stomata apertures, cold stress tolerance as well as other aspects of its emerging roles such as balancing flowering and root growth in response to drought.
Potassium (K) is the most abundant cation in the vast majority of plants. It is required in large quantities which, in an agronomic context, typically necessitates application of K in the form of potash or other K fertilisers. Recently, the price of K fertiliser has risen dramatically, a situation that is paralleled by increasing K deficiency of soils around the globe. A potential solution to this problem is to reduce crop K fertiliser dependency by replacing it with sodium (Na) fertiliser which carries a much smaller price tag. In this paper we discuss the physiological roles of K and Na and the implications of Na fertilisation for crop cultivation and soil management. By using greenhouse growth assays we show distinct growth promotion after Na fertilisation in wheat, tomato, oilseed and sorghum. Our results also show that up to 60% of tissue K can be substituted by Na without growth penalty. Based on these data, simple economic models suggest that (part) replacement of K fertiliser with Na fertiliser leads to considerable savings.
Salinity is a global issue limiting efficient agricultural production. Nanobiotechnology has been emerged as an effective approach to improve plant salt tolerance. However, little known is about the shared mechanisms between different nanomaterials-enabled plant salt tolerance. In this study, we found that both PNC [polyacrylic acid coated nanoceria (CeO2 nanoparticles)] and PMO (polyacrylic acid coated Mn3O4 nanoparticles) nanozymes improved rapeseed salt tolerance. PNC and PMO treated rapeseed plants showed significantly fresh weight, dry weight, higher chlorophyll content, Fv/Fm, and carbon assimilation rate than control plants under salt stress. Results from confocal imaging with reactive oxygen species (ROS) fluorescent dye and histochemical staining experiments showed that the ROS over-accumulation level in PNC and PMO treated rapeseed was significantly lower than control plants under salt stress. Confocal imaging results with K+ fluorescent dye showed that significantly higher cytosolic and vacuolar K+ signals were observed in PNC and PMO treated rapeseed than control plants under salt stress. This is further confirmed by leaf K+ content data. Furthermore, we found that PNC and PMO treated rapeseed showed significantly lower cytosolic Na+ signals than control plants under salt stress. While, compared with significantly higher vacuolar Na+ signals in PNC treated plants, PMO treated rapeseed showed significantly lower vacuolar Na+ signals than control plants under salt stress. These results are further supported by qPCR results of genes of Na+ and K+ transport. Overall, our results suggest that besides maintaining ROS homeostasis, improvement of leaf K+ retention could be a shared mechanism in nano-improved plant salt tolerance.
Current measures mainly focus on how melatonin reduces physiological heat stress in animals, but its effects on reproductive damage to male dairy goats have been neglected. This study aimed to determine the protective effect of melatonin on male reproduction during heat stress in dairy goats and to further explore its mechanisms. A natural heat stress model of Saanen dairy goats was used to assess testicular tissue damage 7 days after heat stress and to examine semen quality changes during a spermatogenic cycle. RNA-seq, Western blot, RT–qPCR, and immunofluorescence staining were used to explore the mechanism by which melatonin protects against heat stress-induced reproductive damage and to validate the results. The data suggested that melatonin significantly alleviated the heat stress-induced decrease in sperm quality, protected varicose tubule structure, reduced the levels of heat shock proteins and apoptotic proteins and protected the spermatocytes and round spermatozoa, which are mainly affected by heat stress. RNA-seq results suggest that melatonin inhibits the PI3K/AKT signaling pathway, reduces the level of p-AKT, and promotes elevated BCL-2. In addition, melatonin treatment could upregulate the gene expression of MT2 which was downregulated by heat stress and improve the change in extracellular matrix components and restore serum testosterone levels. Our results suggest that melatonin can protect against testicular and spermatogenic cell damage and improve semen quality in male dairy goats under heat stress. This study provides an important reference for subsequent studies on the molecular mechanisms of melatonin in protecting male reproductive processes under heat stress and using exogenous melatonin to prevent heat stress.
This paper reported a wine-derived lactic acid bacterium, Lactiplantibacillus plantarum XJ25, which exhibited higher cell viability under acid stress upon methionine supplementation. Cellular morphology and the composition of the cytomembrane phospholipids revealed a more solid membrane architecture presented in the acid-stressed cells treated with methionine supplementation. Transcriptional analysis showed L. plantarum XJ25 reduced methionine transport and homocysteine biosynthesis under acid stress. Subsequent overexpression assays proved that methionine supplementation could alleviate the cell toxicity from homocysteine accumulation under acid stress. Finally, L. plantarum XJ25 employed energy allocation strategy to response environmental changes by balancing the uptake methionine and adjusting saturated fatty acids (SFAs) in membrane. These data support a novel mechanism of acid resistance involving methionine utilization and cellular energy distribution in LAB and provide crucial theoretical clues for the mechanisms of acid resistance in other bacteria.
Corynebacterium glutamicum is a promising chassis microorganism for the bioconversion of lignocellulosic biomass owing to its good tolerance and degradation of the inhibitors generated in lignocellulosic pretreatments. Among the identified proteins encoded by genes within the C. glutamicum genome, nearly 400 are still functionally unknown. Based on previous transcriptome analysis, we found that the hypothetical protein gene cgl2215 was highly upregulated in response to phenol, ferulic acid, and vanillin stress. The cgl2215 deletion mutant was shown to be more sensitive than the parental strain to phenolic compounds as well as other environmental factors such as heat, ethanol, and oxidative stresses. Cgl2215 interacts with C. glutamicum mycoloyltransferase A (MytA) and enhances its in vitro esterase activity. Sensitivity assays of the ΔmytA and Δcgl2215ΔmytA mutants in response to phenolic stress established that the role of Cgl2215 in phenolic tolerance was mediated by MytA. Furthermore, transmission electron microscopy (TEM) results showed that cgl2215 and mytA deletion both led to defects in the cell envelope structure of C. glutamicum, especially in the outer layer (OL) and electron-transparent layer (ETL). Collectively, these results indicate that Cgl2215 can enhance MytA activity and affect the cell envelope structure by directly interacting with MytA, thus playing an important role in resisting phenolic and other environmental stresses.
To cope with fluctuating light conditions, terrestrial plants have evolved precise regulation mechanisms to help optimize light capture and increase photosynthetic efficiency. Upon blue light-triggered autophosphorylation, activated phototropin (PHOT1 and PHOT2) photoreceptors function solely or redundantly to regulate diverse responses, including phototropism, chloroplast movement, stomatal opening, and leaf positioning and flattening in plants. These responses enhance light capture under low-light conditions and avoid photodamage under high-light conditions. NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3) and ROOT PHOTOTROPISM 2 (RPT2) are signal transducers that function in the PHOT1- and PHOT2-mediated response. NPH3 is required for phototropism, leaf expansion and positioning. RPT2 regulates chloroplast accumulation as well as NPH3-mediated responses. NRL PROTEIN FOR CHLOROPLAST MOVEMENT 1 (NCH1) was recently identified as a PHOT1-interacting protein that functions redundantly with RPT2 to mediate chloroplast accumulation. The PHYTOCHROME KINASE SUBSTRATE (PKS) proteins (PKS1, PKS2, and PKS4) interact with PHOT1 and NPH3 and mediate hypocotyl phototropic bending. This review summarizes advances in phototropic growth and chloroplast movement induced by light. We also focus on how crosstalk in signaling between phototropism and chloroplast movement enhances weak light capture, providing a basis for future studies aiming to delineate the mechanism of light-trapping plants to improve light-use efficiency.
Ultraviolet-B (UV-B) light is an intrinsic part of sunlight that reaches the earth’s surface, and affects plant survival and adaptation. How plants respond to UV-B light is regulated by the wavelength, intensity and duration of UV-B radiation, and is also regulated by photosynthetically active radiation perceived by phytochrome and cryptochrome photoreceptors. Non-damaging UV-B light promotes plant photomorphogenesis and UV-B acclimation which enhances plant tolerance against UV-B stress. However, high-level UV-B radiation induces DNA damage, generates reactive oxygen species (ROS) and impairs photosynthesis. Plants have evolved efficient mechanisms to utilize informational UV-B signal, and protect themselves from UV-B stress. UV RESISTANCE LOCUS8 (UVR8) is a conserved plant-specific UV-B photoreceptor. It interacts with CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) to initiate UV-B-specific light signaling and regulate UV-B responsive gene expression. A set of transcription factors such as ELONGATED HYPOCOTYL5 (HY5) function downstream of the UVR8-COP1 module to promote seedling de-etiolation for photomorphogenic development and biosynthesis of sunscreen flavonoids for UV-B stress tolerance. In addition to UVR8 signaling pathways, plants subjected to damaging UV-B radiation initiate stress protection and repair mechanisms through UVR8-independent pathways. In this review, we summarize the emerging mechanisms underlying UV-B stress acclimation and protection in plants, primarily revealed in the model plant Arabidopsis thaliana.
Potassium (K) is a major essential element in plant cells, and KUP/HAK/KT-type K+ transporters participate in the absorption of K+ into roots and in the long-distance transport to above-ground parts. In Arabidopsis thaliana, KUP9 is involved in the transport of K+ and Cs+ in roots. In this study, we investigated KUP9 function in relation to the K+ status of the plant. The expression of KUP9 was upregulated in older leaves on K+-depleted medium, compared to the expression of the other 12 KUP genes in the KUP/HAK/KT family in Arabidopsis. When grown on low K+ medium, the kup9 mutant had reduced chlorophyll content in seedlings and chlorosis in older rosette leaves. Tissue-specific expression of KUP9 determined by KUP9 promoter:GUS assay depended on the K+ status of the plants: In K+ sufficient medium, KUP9 was expressed in the leaf blade towards the leaf tip, whereas in K+ depleted medium expression was mainly found in the petioles. In accordance with this, K+ accumulated in the roots of kup9 plants. The short-term 43K+ tracer measurement showed that 43K was transferred at a lower rate in roots and shoots of kup9, compared to the wild type. These data show that KUP9 participates in the distribution of K+ in leaves and K+ absorption in roots under low K+ conditions.
Growing concern around global warming has led to an increase in research focused on plant responses to increased temperature. In this review, we highlight recent advances in our understanding of plant adaptation to high ambient temperature and heat stress, emphasizing the roles of plant light signaling in these responses. We summarize how high temperatures regulate plant cotyledon expansion and shoot and root elongation and explain how plants use light signaling to combat severe heat stress. Finally, we discuss several future avenues for this research and identify various unresolved questions within this field.
Microbial species often occur in complex communities and exhibit intricate synergistic and antagonistic interactions. To avoid predation and compete for favorable niches, bacteria have evolved specialized protein secretion systems. The type VI secretion system (T6SS) is a versatile secretion system widely distributed among Gram-negative bacteria that translocates effectors into target cells or the extracellular milieu via various physiological processes. Pseudomonas aeruginosa is an opportunistic pathogen responsible for many diseases, and it has three independent T6SSs (H1-, H2-, and H3-T6SS). In this study, we found that the H3-T6SS of highly virulent P. aeruginosa PA14 is negatively regulated by OxyR and OmpR, which are global regulatory proteins of bacterial oxidative and acid stress. In addition, we identified a H3-T6SS effector PA14_33970, which is located upstream of VgrG3. PA14_33970 interacted directly with VgrG3 and translocated into host cells. Moreover, we found that H3-T6SS and PA14_33970 play crucial roles in oxidative, acid, and osmotic stress resistance, as well as in motility and biofilm formation. PA14_33970 was identified as a new T6SS effector promoting biofilm formation and thus named TepB. Furthermore, we found that TepB contributes to the virulence of P. aeruginosa PA14 toward Caenorhabditis elegans. Overall, our study indicates that H3-T6SS and its biofilm-promoting effector TepB are regulated by OxyR and OmpR, both of which are important for adaptation of P. aeruginosa PA14 to multiple stressors, providing insights into the regulatory mechanisms and roles of T6SSs in P. aeruginosa.
In nature, organisms face multiple abiotic stress concurrently. Our previous study has indicated how threshold level of lethality depends on the type and combination of stressors. Many mechanisms exist by which organisms respond to stressors and maintain homeostasis. We examined the homeostatic pliability in an extremophilic oriental midge Chironomus ramosus larvae under various combinatorial stress conditions of desiccation (DS), heat (HS) and starvation (SS). Exposure to these stressors led to activation of a common response pathway of oxidative stress. Abundance of antioxidant enzymes like superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase along with selective as well as stressor specific increase in total antioxidant capacity were reflected from the corresponding level of reactive oxygen and nitrogen species (RONS) in larvae exposed to various combinatorial stress. Additionally, we found stressor specific increment in lipid peroxidation level, protein carbonyl content and advanced oxidative protein products during the stress regime. Further investigation revealed a sharp decline in the activity of mitochondrial aconitase enzyme activity in response to abiotic stress induced oxidative stress. The combinatorial stressor specific comparative study based on biochemical and fluorescence based redox-endpoint assays confirmed that the generation of oxidative stress is the consequential convergent pathway of DS, HS and SS, but the quantum of RONS decides the redox potential of homeostatic response and survival rate.
Heat stress has multiple potential effects on the brain, such as neuroinflammation, neurogenesis defects, and cognitive impairment. β-hydroxybutyric acid (BHBA) has been demonstrated to play neuroprotective roles in various models of neurological diseases. In the present study, we investigated the efficacy of BHBA in alleviating heat stress-induced impairments of adult hippocampal neurogenesis and cognitive function, as well as the underlying mechanisms. Mice were exposed to 43 ℃ for 15 min for 14 days after administration with saline, BHBA, or minocycline. Here, we showed for the first time that BHBA normalized memory ability in the heat stress-treated mice and attenuated heat stress-impaired hippocampal neurogenesis. Consistently, BHBA noticeably improved the synaptic plasticity in the heat stress-treated hippocampal neurons by inhibiting the decrease of synapse-associated proteins and the density of dendritic spines. Moreover, BHBA inhibited the expression of cleaved caspase-3 by suppressing endoplasmic reticulum (ER) stress, and increased the expression of brain-derived neurotrophic factor (BDNF) in the heat stress-treated hippocampus by activating the protein kinase B (Akt)/cAMP response element binding protein (CREB) and methyl-CpG binding protein 2 (MeCP2) pathways. These findings indicate that BHBA is a potential agent for improving cognitive functions in heat stress-treated mice. The action may be mediated by ER stress, and Akt-CREB-BDNF and MeCP2 pathways to improve adult hippocampal neurogenesis and synaptic plasticity.