BcSRC2 interacts with BcAPX4 to increase ascorbic acid content for responding ABA signaling and drought stress in Pak-choi

Abstract As a reducing substance, ascorbic acid functed well in abiotic and biotic stress. However, the regulatory mechanism of drought resistance is rarely known in pak-choi. Here we found a gene BcSRC2 containing a C2 domain that responds to ABA signal and drought regulation in pak-choi. Silencing of BcSRC2 reduces ascorbic acid content and drought resistance of pak-choi. In Arabidopsis, BcSRC2 overexpression promotes ascorbic acid accumulation and increases drought tolerance. Meanwhile, transcriptome analysis between WT and BcSRC2-overexpressing pak-choi suggests that ascorbic acid-related genes are regulated. BcSRC2 interacts with BcAPX4 and inhibit APX activity in vitro and in vivo, increasing the ascorbic acid content. We also found that drought stress increases ABA content, which reduces the expression of BcMYB30. BcMYB30 bound to the promoter of BcSRC2 and reduced its expression. Overall, our results suggest that a regulatory module, BcMYB30-BcSRC2-BcAPX4, plays a central role in increasing ascorbic acid content for responding ABA-mediated drought regulation in pak-choi.