CsVOZ2 enhances drought and salt tolerance by activating CsGalUR1 and CsGalUR2 expression in cucumber

Abiotic stresses, such as drought and salinity, significantly restrict plant growth and crop yield. Ascorbic acid (AsA), the predominant water-soluble antioxidant in plants, plays a crucial role in scavenging reactive oxygen species and enhancing stress tolerance. In this study, a VOZ transcriptional factor, CsVOZ2, was identified in cucumber, which enhances drought and salt tolerance by regulating AsA synthesis. CsVOZ2 was primarily expressed in vascular bundles and was significantly induced by drought and salt treatments. Genome-edited knockout alleles, CR#1 and CR#2, exhibited increased susceptibility to drought and salt under 20% PEG 6000 and 200 mM NaCl conditions, with reduced ABA levels, compromised ABA-dependent stomatal closure, and increased water loss rates. DNA affinity purification sequencing and RT-qPCR analyses revealed that galacturonic acid reductase genes CsGalUR1 and CsGalUR2, involved in AsA synthesis, were downregulated in CR#1 and CR#2 mutants. Furthermore, yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays demonstrated that CsVOZ2 directly binds to the palindromic sequence GC(G/T)TNx7A(A/C)G(C/G) in the promoter regions of CsGalUR1 and CsGalUR2, activating their expression and promoting AsA synthesis. These findings demonstrate that CsVOZ2 acts as a positive regulator of AsA-mediated drought and salt tolerance, highlighting its potential as a target for improving abiotic stress resistance in cucumber.