Natural variation in VrERF088 modulates drought tolerance during mungbean germination

Drought stress is a major global challenge in crop production. The occurrence of drought during seed germination directly affects crop establishment and final yield. In this work, we performed whole-genome resequencing of 414 mungbean (Vigna radiata (L.) R. Wilczek) germplasms and identified 4,875,142 high-quality single-nucleotide polymorphisms (SNPs). Two seed germination traits of the mungbean panel under drought stress across two environments were evaluated via a genome-wide association study (GWAS), and the results revealed a significant quantitative trait locus (QTL). Additionally, kompetitive allele-specific PCR (KASP) markers that can identify the germination characteristics of mungbean seeds under drought stress were developed and verified. Moreover, among the nine candidate genes near this site, the expression levels of different haplotypes of VrERF088 differed. Interestingly, the only ABA-responsive element in the VrERF088 promoter was mutated. The results demonstrated that VrABI5 activates the transcriptional activity of the Hap1 promoter by binding to the ABRE motif. The overexpression of VrERF088 in Arabidopsis thaliana significantly reduced the germination rate of plants under drought stress by increasing the expression of the ABA response genes AtPM6 and AtLEA4 and reducing the expression of the germination-related genes AtEXPAs, resulting in hypersensitivity to ABA. Our results indicate that mutation of the ABRE motif in the VrERF088 promoter results in a relatively high germination rate under drought stress.