RNA interference (RNAi) has emerged as a key molecular tool in various commercially important decapod crustaceans, offering potential biotechnological applications in aquaculture. However, in the tropical rock lobster Panulirus ornatus, gene silencing through RNAi has proven difficult to achieve despite the availability of extensive omics data. This study investigates the RNAi response across life stages in P. ornatus, focusing on larvae and juveniles to determine when the species is most receptive to RNAi. Late-stage phyllosoma larvae and early juveniles were microinjected with dsRNA for the insulin-like growth factor binding protein encoding gene to determine silencing efficiency. Our results show that while juveniles exhibit an efficient systemic RNAi response with robust silencing across tissues, larvae display limited silencing capacity. A key finding is the differential expression of RNAi pathway components, including SID1, which facilitates dsRNA uptake in juveniles but is less active in larvae. Fluorescent microscopy revealed that dsRNA is rapidly sequestered and expelled by the antennal gland in larvae, potentially limiting RNAi efficacy. To further explore the mechanisms underlying RNAi in P. ornatus, RNA-seq analysis was conducted on pleopods collected across time points after dsRNA exposure in juvenile lobsters. Transcriptomic analysis identified significant upregulation of RNAi machinery, including Dicer-2, Argonaute-2, and SID1, which are critical for silencing. Additionally, several genes associated with antiviral responses were differentially expressed, suggesting broader involvement of RNAi in immune regulation. These findings highlight the potential to enhance RNAi strategies in P. ornatus juveniles, advancing the development of RNAi-based tools for disease resistance and productivity in aquaculture.

Dicyemids (phylum Dicyemida), primarily found in the renal organs of coleoid cephalopods, are a unique group of morphologically simple parasites with global distribution. Here, we investigated the diversity and prevalence of dicyemid communities in a wide range of cephalopod hosts across four geographic zones (the North East Atlantic, Mediterranean Sea, China Sea in the Western North Pacific, and Australia in the South Pacific) using Illumina sequencing of the 18S rDNA amplicons. Across 227 host samples, we identified 482 amplicon sequence variants, which clustered into 95 genetic types. The results indicated a higher number of distinct genetic types within Dicyemida than those currently identified through morphology-based taxonomy. Our finding of 46 dicyemid types in the common cuttlefish (Sepia officinalis) contrasts sharply with the previous records of a maximum of four species in this host. Furthermore, only a few host species exhibited a single dicyemid type, while most harbored multiple types; several types were distributed worldwide. Additionally, we identified eight new cephalopod hosts in the Pacific. Analyses of community (α) diversity suggested the unique character of certain geographical areas, such as the Bass Strait (Australia). β-diversity analyses confirmed that geographic location and host species were significant determinants of the dicyemid community composition. These results suggest that current species classifications may underestimate the true diversity of dicyemids. They emphasize the intricate interplay between geography, host specificity, and dicyemid community diversity.

Ribonucleotide reductase large subunit (RRM1) functions as the catalytic subunit of ribonucleotide reductase (RR), which is a rate-limiting enzyme involved in DNA synthesis and repair. In this study, an RRM1 gene was identified from Macrobrachium nipponense and designated as MnRRM1. Its complete cDNA sequence was 2941 bp, encoding 812 amino acids. Quantitative real-time PCR (qRT-PCR) indicated that MnRRM1 expression was most pronounced in stage V of ovary development compared to the other stages. Fluorescence in situ hybridization localized the MnRRM1 mRNA to the oocyte cytoplasm and to the follicular cells surrounding the oogonia and previtellogenic oocytes. Immunohistochemistry (IHC) localized the MnRRM1 protein to the nucleus of oogonia, as well as the cytoplasm and nucleus of oocytes. Ovarian explant incubation with AICA riboside (AICAR) and in vivo injection with 5-hydroxytryptamine (5-HT) upregulated the expression of the cell cycle protein B (MnCYCLIN B), cell division cyclin 2 (MnCDC2), and mitogen-activated protein kinase (MnMAPK) genes. In contrast, the wee1 protein (MnWEE1) and nm23 nucleoside diphosphate kinase (MnNM23) genes were downregulated. However, the outcomes of gemcitabine (GEM) incubation and RNA interference (RNAi) demonstrated an inverse pattern. Furthermore, RNAi-based MnRRM1 knockdown delayed oocyte maturation. These findings imply that MnRRM1 plays a potentially crucial role in promoting ovarian maturation in M. nipponense by facilitating DNA synthesis and energy provision during oocyte development and maturation.

Chitons, known as marine living fossils, have retained their ancestral traits for approximately 300 million years. The genus Acanthochitona (Polyplacophora: Acanthochitonidae), characterized by the presence of 9 pairs of sutural tufts on a well-expanded girdle, is distributed across the intertidal zones of South Korea, Japan, China, and the Indo-Pacific. This study examined five Acanthochitona species from South Korea: A. achates, A. circellata, A. defilippii, A. rubrolineata, and A. feroxa sp. nov. Their mitochondrial genome sequences ranged from 14,986 to 15,006 bp in length and with a gene content typical for Polyplacophora. Genetic (including a transitive consistency score [TCS] genetic network), principal coordinate, phylogenetic network, and CO1-based barcoding gap analyses confirmed a new species, A. feroxa sp. nov., which exhibited morphologically distinct dorsal spicules and radulae. Maximum likelihood (ML) and Bayesian inference (BI) trees were constructed based on the CO1 sequences of 28 polyplacophoran species belonging to 9 families, which placed these five Acanthochitona species within a monophyletic family, Acanthochitonidae. The analyses also indicated the polyphyletic nature of Mopaliidae, recommending a reclassification. Divergence time estimation revealed that Acanthochitona deviated during the Late Cretaceous (ca. 83.94 mya), with continued speciation occurring in the Paleogene and Neogene periods. Additionally, we constructed a pictorial key based on the ML tree for morphologically identifying the five Acanthochitona species. This study contributes to the understanding of speciation and phylogenetic relationships within the Acanthochitonidae, offering valuable insights into the classification scheme and mitochondrial genome evolution of chitons in the western Pacific.

Transcription factor IIIA (TFIIIA) is a zinc finger protein that facilitates the assembly of a transcription complex by recruiting transcription factors TFIIIB and TFIIIC, along with RNA polymerase III, to initiate the transcription of 5S rRNA genes. However, the effects of TFIIIA knockout in vertebrates remain unclear. To address this, we investigated the function of a homologous general transcription factor IIIAa, gtf3aa, identified as a maternal factor in zebrafish. During early embryonic development, gtf3aa expression initially increased and subsequently declined. At 12 h postfertilization, gtf3aa mRNA was detected at notably low levels in the embryo, whereas by three days postfertilization, its mRNA level gradually increased in the larvae. The gtf3aa was broadly expressed in various embryonic tissues of zebrafish, with higher expression levels observed in the brain, heart, liver, and muscle. Knockout of gtf3aa significantly suppressed somatic 5S rRNA transcription in early zebrafish embryos and larvae, resulting in a reduction in the number of mature monoribosomes and polyribosomes. The gtf3aa^−/− larvae exhibited slow growth and delayed yolk absorption, along with impaired development of the eyes, heart, swim bladder, liver, and intestinal tissues. Additionally, expression of genes involved in metabolic signaling pathways, including the peroxisome proliferator-activated receptor pathway, was reduced. The gtf3aa^−/− zebrafish did not survive beyond seven days postfertilization. This study offers preliminary insights into the role of gtf3aa in regulating somatic 5S rRNA transcription and embryonic organ development in zebrafish.

Interleukin-18 (IL-18) is an important proinflammatory cytokine essential for immune modulation. Unlike most cytokines, it is synthesized as an inactive precursor, with its maturation and secretion being critical for its functionality. As an evolutionarily ancient cytokine, it can be traced back to teleosts, but not zebrafish. However, the regulatory mechanism of IL-18 in early vertebrates remains largely elusive. The present study reports the maturation and secretion of IL-18 along with its role in signal transduction in a teleost fish half-smooth tongue sole (Cynoglossus semilaevis). We found that pro-IL-18 was cleaved by caspase-1, caspase-3/7, and caspase-6 at different N-terminal sites, generating three forms of the mature IL-18. In contrast to the negatively charged pro-IL-18, the positively charged mature IL-18 is highly enriched in the cytoplasmic membrane. It is enclosed within membrane-associated microvesicles, which facilitate secretion to the extracellular milieu. Once secreted, it binds specifically to the IL-18 receptor α (IL-18Rα) present on the cell surface and recruits IL-18Rβ to form a functionally active heterotrimeric complex. Bacterial challenge induces the maturation and secretion of IL-18, which upregulates the expression of the proinflammatory cytokines. Activation of the IL-18-mediated signaling pathway enhances antimicrobial immunity and reduces infection-induced mortality. Our findings collectively reveal a unique mechanism of IL-18 maturation, unconventional secretion, and immune regulation in a teleost fish, which provides new insights into the role of IL-18-based signaling in immune regulation.

While Isochrysis zhanjiangensis, a marine microalga, has been widely adopted in aquaculture for its health-promoting properties, its potential as a functional food for human metabolic health remains unexplored. To bridge this gap, this study systematically evaluated the nutritional composition, biosafety, and therapeutic efficacy of I. zhanjiangensis against high-fat diet (HFD)-induced metabolic disorders in mice. Our results revealed that I. zhanjiangensis exhibits a desirable nutritional profile with no detectable toxicity, and its dietary supplementation significantly attenuated HFD-induced metabolic dysregulation. Gut microbiota profiling further demonstrated that I. zhanjiangensis supplementation restored microbial homeostasis, evidenced by mitigation of the elevated Firmicutes/Bacteroidota ratio and enrichment of beneficial genera including Muribaculum, Candidatus_Arthromitus, and Veillonella. Hepatic metabolomics identified key metabolites modulated by I. zhanjiangensis, such as N1-methyl-2-pyridone-5-carboxamide, N-acetyl-L-histidine, and eicosapentaenoic acid, which are mechanistically linked to lipid metabolism regulation. These findings not only position I. zhanjiangensis as a promising candidate for functional food development targeting HFD-induced metabolic dysregulation, but also highlight the untapped potential of aquaculture microalgae as sustainable resources for nutraceutical innovation.

Inflammation plays a crucial role in defending the host against pathogens and other harmful stimuli. However, uncontrolled acute inflammation has been implicated in a multitude of diseases, including those that affect aquatic animals. While the processes that initiate the inflammatory response are relatively well understood, the roles of lipids, their derivatives, and the mechanisms by which they contribute to alleviating acute inflammation remain less well characterized. In the present study, lipidomic analyses were performed to identify changes in lipid metabolism in the coelomocytes of the sea cucumber Apostichopus japonicus after infection with Vibrio splendidus. The omics data indicated significant increases in specific sterols, including desmosterol, 25-hydroxycholesterol, and 24,25-epoxycholesterol, during the late phase of the inflammatory response. The accumulation of these sterols was found to be responsible for the suppression of A. japonicus interleukin-17 (AjIL-17)-mediated inflammatory response. A subsequent biolayer interferometry assay revealed that A. japonicus liver X receptor (AjLXR) served as the downstream receptor of these sterols. The knockdown of AjLXR reversed the desmosterol-dependent suppression of AjIL-17 expression. Conversely, the activation of AjLXR by the synthetic agonist GW3965 inhibited the expression of AjIL-17 induced by infection with V. splendidus or stimulation with LPS. Moreover, AjLXR repressed AjIL-17 transcription by directly binding to the AjIL-17 promoter in a SUMOylation-independent manner. In conclusion, our findings highlight the crucial role of the sterols–LXR axis in mitigating IL-17-mediated acute inflammation, suggesting that targeting this axis could be a promising strategy for preventing and treating chronic inflammation-associated diseases.

Carbohydrate-induced glycogenic hepatopathy is underdiagnosed and difficult to discriminate from hepatic steatosis in humans. The present study used liver biopsy and other diagnostic tools, and adopted metabolomic technology to identify glycogenic hepatopathy rather than hepatic steatosis in largemouth bass induced by high carbohydrate diet (HC). HC induced obvious liver injury in largemouth bass with disarranged hepatocytes, partial cell membrane damage, and irregular distribution of nuclei, accompanied by increased serum ALT and AST activities. PAS staining and glycogen content analysis detected significant increases in liver glycogen content, whereas intrahepatic triglyceride content and programmed cell death were not affected. Metabolomic analysis indicated that up-regulated metabolites were mainly enriched in glycogen synthesis precursors, whereas betaine and unsaturated fatty acids were down-regulated, confirming that HC induced glycogenic hepatopathy rather than hepatic steatosis in largemouth bass. The significantly decreased betaine in both serum and liver of largemouth bass served as a potential key regulator in such disease, whose supplementation could alleviate HC-induced liver injury and serum ALT activity. Betaine supplementation increased betaine and carnitine contents in liver and serum, resulting in decreased hepatic glycogen deposition and cortisol content in largemouth bass. Further study showed that dietary betaine significantly improved the capacity of largemouth bass to resist against ammonia stress. Therefore, our study established a glycogenic hepatopathy-inducing and evaluation model in a primitive teleost and also identified the betaine as the key metabolic marker and prevent strategy, which help advance the understanding of human liver diseases.

Non-small cell lung cancer (NSCLC) remains a major cause of cancer-related mortality worldwide, emphasizing the need for novel therapeutic strategies. In this study, we demonstrate that homoyessotoxin (hYTXs), a marine-derived natural compound, exerts potent anti-NSCLC progression. Network pharmacology, molecular docking, molecular dynamics simulations, and SPR analysis confirmed a strong binding affinity between hYTXs and EGFR. Mechanistically, hYTXs disrupted EGFR trafficking by accelerating its endocytosis and enhancing its accumulation within lysosomes, thereby accelerating receptor degradation without altering EGFR mRNA levels. CHX chase and lysosomal inhibition assays further verified that hYTXs downregulated EGFR through post-translational regulation. This degradation led to suppression of downstream PI3K/AKT/ERK signaling, reduced phosphorylation of FOXO3a and p70S6K, and enhanced PTEN nuclear translocation. Functionally, hYTXs induced apoptosis, oxidative stress, S-phase arrest, mitochondrial dysfunction, and DNA damage in A549 cells, with comparable inhibitory potency in EGFR-mutant lines (PC9, H1975) but minimal cytotoxicity toward normal lung epithelial cells. In vivo, hYTXs significantly inhibited tumor growth and exhibited excellent safety based on serum biochemistry and lung histology. Collectively, hYTXs represents a promising next-generation EGFR-targeting compound that overcomes kinase-mutation-driven resistance by promoting receptor degradation rather than kinase inhibition.

The occurrence and development of tumors rely on the nutritional supply from blood vessels, which also serve as the main pathway for tumor metastasis. Inhibiting angiogenesis is one of the main strategies for cancer treatments. Chiral drugs, encouraged and inspired by chiral natural products, make up a major portion of marketed drugs. However, as an important source for synthetic chemistry and drug discovery, the counterpart of chiral natural products, the enantiomers, has received little attention. Here, we constructed a compound library containing 100 racemates ( ±)-1–100 and 4 pairs of enantiomers (33, 48, 59, 68) of 3,4-dioxygenated-4-aryl-quinolin-2(1H)-one alkaloids. Through extensive activity screening, we found that the compounds with 3R, 4R configuration, opposite to the natural products, exhibited potent angiogenesis inhibitory activity in zebrafish, while the 3S, 4S-configured natural derivatives have no effects. More importantly, compound ( +)-48, named as (3R, 4R)-CHNQD-00728, significantly inhibited hepatic tumor growth in doxycin hydrochloride-induced liver-specific enlargement zebrafish. Examining the phenomenon and unlocking dark matter of enantiomeric natural products in innovative drugs discovery can provide a new perspective on organic synthesis and medicinal chemistry, thus enabling a broader exploration.

Fungal iterative type I polyketide synthases (iPKSs) are commonly classified into nonreducing (NR-), partially reducing (PR-), and highly reducing (HR-) polyketide synthases based on their assembly mechanisms and domain structures. These iPKSs have been considered functionally and evolutionarily distinct, characterized by clear boundaries. However, emerging genomic analyses suggest that the diversity of iPKSs in fungi is far from fully understood. Here, we describe the discovery and characterization of PbPKS1 from a marine-derived fungus Penicillium brocae HDN12-143, which exhibits an atypical domain organization arranged as KR-KS-AT-PT-ACP₁-ACP₂-CMeT-TE. Heterologous expression of PbPKS1 resulted in the production of two monohydroxybenzoic acids and two pyrones. In vivo and in vitro characterizations demonstrated that PbPKS1 has the capability to synthesize Cα-methylated partially reducing polyketides, yet involved a NR-PKS-like assembly mechanism, featuring a product template (PT) domain for aldol cyclization and a C-terminal thioesterase (TE) domain for product release. Phylogenetic analysis suggests that PbPKS1 belongs to a non-canonical PR-PKS (nPR-PKS) family, which is a minor grouping across the fungal kingdom, and possibly evolved from an NR-PKS through gene recombination. The discovery of nPR-PKS not only expands the diversity of iPKSs but also provides new insights into the evolutionary development of fungal iPKSs.

Vibrio parahaemolyticus is a marine bacterium and a causative agent of gastroenteritis in humans. Phages targeting V. parahaemolyticus serve as natural antagonists to this pathogen, significantly controlling its population and, consequently, disease outbreaks. In this study, two myoviruses, vB_VpaM_R20L (R20L) and vB_VpaM_R19R (R19R), were isolated and characterized against V. parahaemolyticus ATCC 17802 ^T. Despite their genomic resemblance, phages R19R and R20L displayed notable differences in physiological characteristics, particularly in infection dynamics and thermal stability. Both phages had a latent period of approximately 10 min; however, R19R demonstrated significantly greater replication efficiency, with a burst size of 388 PFU/cell compared to 90 PFU/cell for R20L. Thermal stability assays showed that R20L maintained survival rates of 80%–100% at 5 °C–45 °C for over three days, while R19R’s viability declined to 50% within 12 h under the same conditions. Furthermore, molecular dynamics simulations identified the influence of temperature on the thermal stability of phages, primarily through impact on the structural proteins. These findings suggest that subtle genomic variations may drive differences in physiological characteristics, highlighting the complexity of vibriophage-host interactions and their selection in response to natural environmental pressures.

Methylmercury (MeHg) is a potent neurotoxin and bioaccumulates in food webs. Microbial transformation of inorganic mercury (Hg) produces most of the MeHg in the marine environment. The gene pair hgcAB encodes for Hg methylation, a process predominantly attributed to anaerobic bacteria. However, recent studies indicate the formation of methylmercury in low-oxygen zones within marine water columns, although the mechanisms remain poorly understood. “Blue holes” are marine sinkholes containing redox gradients stratified with depth and high microbial diversity across a range of biogeochemical cycles. Here, we present the first metagenomic analysis focused on the potential for Hg methylation in a blue hole ecosystem. Yongle Blue Hole (YBH), currently the world’s deepest known blue hole, was selected as a representative site to investigate the genetic potential for Hg methylation and to explore the functional capabilities of putative Hg-methylators within this unique environment. Metagenomic analysis showed that the anoxic sulfidic deep water was likely to be a hotspot for Hg methylation, driven by abundant and diverse Deltaproteobacteria. In the suboxic intermediate layer, Nitrospina and Myxococcota dominated the Hg-methylating community. Furthermore, Hg methylators were found to have different lifestyles (free-living or particle-associated) and to occupy distinct ecological niches within the YBH. In addition, the contribution of sinking particles to Hg methylation, especially in the deep anoxic water column, was highlighted. Our study unveils the biodiversity and survival strategies of Hg methylators across distinct environments. The findings suggest that blue holes could serve as model stratified ecosystems for studying Hg methylation processes across different habitats.

Diatoms and dinoflagellates are two pivotal phytoplankton groups present in coastal ecosystems that play key roles in marine food webs and biogeochemical cycles. The diatom-to-dinoflagellate ratio (diat/dino ratio) serves as an indicator of ecosystem status and phytoplankton community dynamics; however, the specific taxa that contribute to its variability remain poorly understood. This study investigated the phytoplankton community composition and diat/dino ratios in the coastal regions of the East China Sea and northern South China Sea during summer using quantitative PCR (qPCR) and 18S rRNA gene pyrosequencing. The qPCR results revealed that diatoms dominated in the estuarine and nearshore waters, whereas dinoflagellates prevailed in the offshore regions. Random Forest analysis identified dissolved oxygen (DO) and the nitrogen-to-phosphorus (N:P) and silicon-to-nitrogen (Si:N) ratios as the primary drivers of variation in the diat/dino ratio. The influence of N:P ratios was further modulated by the absolute nitrogen and phosphorus concentrations. Taxonomic profiling revealed that Thalassiosiraceae and Chaetocerotaceae were enriched in nutrient-rich estuarine waters, while Leptocylindraceae, Bacillariaceae, and Skeletonemaceae dominated in regions with low N:P ratios. In contrast, dinoflagellate families, such as Thoracosphaeraceae, Pyrocystaceae, Peridiniaceae, and Heterocapsaceae, were more abundant in environments with high DO and elevated N:P ratios. Notably, the northward expansion of Scrippsiella (Thoracosphaeraceae) drove changes in the bloom dynamics that threaten the coastal ecosystem balance. These findings demonstrate that nutrient stoichiometry and oxygen availability influence the diat/dino ratio by favoring distinct phytoplankton taxa, thus offering insights into how anthropogenic nutrient inputs shape community structure and guide coastal ecosystem management.