CONICET | Buscador de Institutos y Recursos Humanos

Endogenous gases had emerged as a mainstream topic in signal transduction research both in animals and plants. Among them, hydrogen sulfide (H2S) is a novel signaling molecule with important functions in human physiology that has also been involved in sulfur-induced resistance in plant-pathogen interaction. In plants, it has been shown that L-cysteine desulfhydrase (DES1) produces H2S during L-cysteine metabolism, while O-acetylserine(thiol)lyase (OAS-TL) consumes H2S during L-cysteine synthesis. Even though, enzymatic production of H2S has been already characterized in plants, the mechanism of action and the biology of H2S as a signaling molecule in photosynthetic organisms is still in its infancy. In the present work we report that the H2S donor NaHS induces stomatal closure in Arabidopsis thaliana epidermal peels, in a dose dependent manner. It is known that the hormone abscisic acid (ABA) leads to stomatal closure and when epidermal strips were treated with the DES1 inhibitor PAG or with the H2S scavenger Hypotaurine, guard cell response to ABA was partially blocked, effect that was restored by the exogenous addition of H2S donors. H2S participation in ABA dependent signaling was confirmed using DES1 deficient mutants des1-1 and des1-2, where ABA-dependent stomatal closure is partially impaired. Nitric oxide (NO) promotes stomatal closure acting downstream of the ABA-induced signaling cascade. In order to address whether H2S interact with other components of ABA-signaling cascade we induced stomatal closure with NaHS in absence or presence of the NO scavenger cPTIO. In presence of cPTIO, H2S is impaired to induce stomatal closure, suggesting that there is a crosstalk between H2S and NO regulated pathways. Altogether, in this work we show that H2S participates in ABA-dependent stomatal closure, possibly interacting with NO.

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