Loss-of-function of the drought-induced genesGASA3andAFP1confers enhanced drought tolerance inArabidopsis thaliana

Prolonged drought is a major challenge in plant growth, severely affecting development and yield. Enhancing drought tolerance is thus a highly desired goal for agriculture. Here, we report that the loss-of-function of two drought-induced genes,GASA3andAFP1, significantly enhances drought tolerance inArabidopsis thaliana. While constitutive expression ofGASA3andAFP1increased drought sensitivity compared to wild type (WT) plants, agasa3afp1double mutant exhibited superior drought tolerance compared to the single mutants. Enhanced drought tolerance ofgasa3,afp1andgasa3afp1is likely due to reduced water loss caused by smaller stomatal apertures and thus lower transpiration rates. Moreover,gasa3andafp1mutants accumulated higher levels of abscisic acid (ABA) under drought conditions than WT plants, concomitant with a stronger up-regulation of ABA-responsive genes such asRD29A/B,ABF2/3, andABI5. The stronger ABA increase in the mutants seems to result from hydrolysis of abscisic acid-glucosyl ester (ABA-GE) from vacuolar stores via the β-glucosidaseBG2rather than byde-novobiosynthesis. Promoter analysis revealed the presence of ABA-responsive and drought stress-related cis-acting elements within theGASA3andAFP1promoter regions. RT-qPCR confirmed that the expression of both genes increased under drought. However,GASA3induction was significantly reduced in the absence ofAFP1,suggesting thatAFP1is involved in the modulation ofGASA3expression. Our findings identify a novelAFP1/GASA3-driven control circuit that negatively regulates drought tolerance by suppressing stomatal closure and attenuating ABA signalling.