nvolvement of hydrogen sulfide (H2S) in stomatal immunity

DENISE SCUFFI; ROSARIO, PANTALENO; ANGELES, AROCA; CECILIA GOTOR; ALEX COSTA; MARKUS, SCHWARZLÄNDER; ANA MARÍA LAXALT; CARLOS GARCIA-MATA

Mendoza

Congreso; Congreso SAIB 2022 Reunión Anual LVIII; 2022

Stomata are pores in the aerial part of the plants surrounded by a pair of cells, guard cells. The regulationof the pore size is crucial since it allows gas exchange with the environment and the loss of water byevapotranspiration. The regulation of stomatal aperture is key to maintain carbon and waterhomeostasis and also for plant defense since pathogens can enter the plant through the stomatal pore. Hydrogen sulfide (H2S) is a gaseous signaling molecule. In plants, the main enzymatic source is Lcysteine desulfhydrase 1 (DES1) which degrades L-cysteine to H2S, pyruvate and ammonia in the cytosol.The involvement of H2S has been reported both in response to stress and in development processes inplants. Today it is considered that H2S mechanism of action is given mainly by protein persulfidation, aredox posttranslational modification (PTM) in protein cysteine residues. This modification can modify theactivity or localization of the target protein. In our lab, we have demonstrated that exogenous applicationof H2S induces stomatal closure in several plant species involving the participation of other signalingmolecules such as nitric oxide (NO) and reactive oxygen species (ROS). Moreover, in Arabidopsis thalianaendogenous H2S/DES1 participates in pathways that lead to stomatal closure as abscisic acid (ABA) andthe bacterial elicitor flagelin (flg22). Our principal aim is to unveil the signaling pathway and themechanism of action of endogenously produced H2S that lead to stomatal closure in response topathogen perception. Stomatal closure assays, with different pathogen elicitors in isolated epidermalpeels of wild type and des1 mutant Arabidopsis leaves, show that des1 does not respond to flg22 but doesrespond to elf18 and chitin suggesting a specific role of DES1 in flg22 signaling. Moreover, we used theratiometric Orp1-GFP2 biosensor and observed that flg22-induced H2O2 increase is blocked in presenceof H2S scavenger, hypotaurine (HT). We further explored the cytosolic H2O2 dynamics in response to H2Sin rbohD mutant and observed a response that was similar to that of wild type suggesting that H2O2induction by H2S is RBOHD-independent. We also analyze apoplastic ROS burst in response to flg22 in leafdiscs by luminol-based assay. The result demonstrates that DES1 participates in this response since des1mutant induces significantly less ROS than wild type. Finally, we are performing a Dimedone-switch assayon Arabidopsis epidermal peels treated with flg22 in order to identify persulfidation targets. Preliminaryresults show several targets associated to the immune response, suggesting this PTM is an activemechanism in H2S–dependent stomatal closure in response to flg22. Further investigations are neededin order to know the H2S targets and the role of persulfidation during stomatal immunity