LAUSR

Transpiration occurs through stomata. The alteration of stomatal apertures in response to drought stress is an important process associated with water use efficiency (WUE). Trehalose-6-phosphate phosphatase (TPP) family genes have been reported to participate in stomatal aperture adjustment. However, there have been no reports of the trehalose metabolism pathway genes improving WUE, and the upstream signalling pathway modulating these genes is not clear. Here, we demonstrated that a member of the TPP gene family, AtTPPI, confers drought resistance and improves WUE by decreasing stomatal apertures and improving root architecture. The reduced expression of AtTPPI caused a drought-sensitive phenotype, while its overexpression significantly increased drought tolerance. Abscisic acid (ABA)-induced stomatal closure experiments confirmed that AtTPPI mutation increased the stomatal aperture compared to that of wild-type (WT) plants; in contrast, overexpression plants had smaller stomatal apertures than those of WT plants. Moreover, AtTPPI mutation also caused stunted primary root length and compromised auxin transport, while overexpression plants had longer primary root lengths. Yeast one-hybrid assays showed that ABA-responsive element-binding factor1 (ABF1), ABF2 and ABF4 directly regulated AtTPPI expression. In summary, the way AtTPPI responds to drought stress suggests that AtTPPI-mediated stomatal regulation is an important mechanism to cope with drought stress and improve WUE.