Multifaceted regulatory functions of CsBPC2 in cucumber under salt stress conditions

Abstract

BASIC PENTACYSTEINE (BPC) transcription factors are essential regulators of plant growth and development. However, BPC functions and the related molecular mechanisms during cucumber (Cucumis sativus L.) responses to abiotic stresses, especially salt stress, remain unknown. We previously determined that salt stress induces CsBPC expression in cucumber. In this study, Csbpc2 transgene-free cucumber plants were created using a CRISPR/Cas9-mediated editing system to explore CsBPC functions associated with the salt stress response. The Csbpc2 mutants had a hypersensitive phenotype, with increased leaf chlorosis, decreased biomass, and increased malondialdehyde and electrolytic leakage levels under salt stress conditions. Additionally, a mutated CsBPC2 resulted in decreased proline and soluble sugar contents and antioxidant enzyme activities, which led to the accumulation of hydrogen peroxide and superoxide radicals. Furthermore, the mutation to CsBPC2 inhibited salinity-induced PM-H⁺-ATPase and V-H⁺-ATPase activities, resulting in decreased Na⁺ efflux and increased K⁺ efflux. These findings suggest that CsBPC2 may mediate plant salt stress resistance through its effects on osmoregulation, reactive oxygen species scavenging, and ion homeostasis-related regulatory pathways. However, CsBPC2 also affected ABA signaling. The mutation to CsBPC2 adversely affected salt-induced ABA biosynthesis and the expression of ABA signaling-related genes. Our results indicate that CsBPC2 may enhance the cucumber response to salt stress. It may also function as an important regulator of ABA biosynthesis and signal transduction. These findings will enrich our understanding of the biological functions of BPCs, especially their roles in abiotic stress responses, thereby providing the theoretical basis for improving crop salt tolerance.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No.31972480 and 32260800), the Earmarked fund for Modern Agro-industry Technology Research System in China (CARS-25-C-01), the Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (CAASASTIP-IVFCAAS), the Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, Ministry of Agriculture, China, and the Natural Science Foundation of Jiangxi Province (20212BAB215004).

Author contributions

Y.L. and X.Y. conceived and designed the research. S.L., L.M., Q.D., L.L. and A.S. performed the experiments and analysed the data. Y.Y., C.H. and J.W. made important comments on design of the research and article writing. S.L. wrote the paper. Y.L. and M.S. revised the paper. All authors read and approved the final version of the paper.

Data availability

All data in this study are available from the corresponding author on reasonable request.

Conflict of interest

The authors declare no competing interests.

Supplementary data

Supplementary data is available at Horticulture Research online.

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