Regulation of stomatal closure by TCA cycle metabolites in grapevine

Yoshiharu Mimata, Ruhai Gong, Xuanxuan Pei, Guochen Qin, Wenxiu Ye
Institute of Advanced Agricultural Sciences, Peking University, 699 Binhu Rd, Fangzi District, Weifang, Shandong 261325, China

Plants close stomata in response to drought stress to avoid excessive water loss. A major TCA cycle metabolite malate induces stomatal closure through stimulation of Ca2+ signaling and activation of SLAC1 anion channels in Arabidopsis guard cells. However, the effects of the other TCA cycle metabolites on guard cell signaling remain unclear. This study investigated the regulation of stomatal closure by TCA cycle metabolites in grapevine, an important cash crop. Grapevine accumulated TCA cycle metabolites including malate in the leaves after dehydration treatment. Stomatal measurements revealed that malate most effectively induces stomatal closure. Several metabolites increased cytosolic Ca2+ concentration in guard cells expressing a Ca2+ reporter and activated SLAC1 expressed in Xenopus oocytes. Pharmacological analysis with a series of inhibitors showed that malate-induced stomatal closure requires G-proteins and second messengers such as cAMP, cADPR and IP3. These results suggested that the metabolic flux is shifted to accumulate TCA cycle metabolites under water deficiency and that accumulated malate induces stomatal closure via G proteins-mediated signal cascades.