Gasotransmitters in plant signalling: An exciting new field is emerging.

LAMATTINA, LORENZO; SCUFFI, DENISE; GARCÍA-MATA, CARLOS

Exeter

Conferencia; 2nd European Conference on the Biology of Hydrogen Sulfide.; 2013

Nitric Oxide Society

Gaseous molecules are nowadays well established signalling components transmitting inter and intracellular information. Gasotransmitters are synthesized and metabolized by specific enzymatic activities, they possess specific cellular targets and regulate a number of physiological responses directed to keep cellular homeostasis in a changing environment. While typical messenger molecules amplify signal cascades, gasotransmitters act through chemical modification of specific protein targets resulting in a rapid influence on cellular metabolism. In the last decade, findings describing the nitric oxide (NO) functions in plant cell signalling were a breakthrough in plant biology. More recently, hydrogen sulfide (H2S) is emerging as a critical player in plant physiology acting as NO partner in some cases but within a yet unknown and unexplored scenario. Plants control the gas exchange with the environment through the stomatal pore formed by two specialized cells named guard cells (GCs). The physiology of GCs is critical for modulating the aperture of the stomatal pore regulated by the entrance and exit of ions from the GCs mediated through the activation/inhibition of plasma membrane (PM) ion channels. Abscisic acid (ABA) is the master phytohormone controlling stomatal closure under water deficit conditions. We have been able to demonstrate that NO is downstream ABA inducing the cytosolic Ca2+ concentration increase and the Ca2+-mediated inhibition of K+in channels contributing to a net loss of ions from the GCs resulting in stomatal closure. Recent studies in our lab demonstrate that another gasotransmitter H2S induces the stomatal closure through a NO-mediated pathway. The mutants of the plant model Arabidopsis are usually used as genetical tools for unravelling gene functions. The Arabidopsis mutant atdes1 defective in cystein desulfhydrase, one of the enzymes responsible of H2S synthesis, do not respond to ABA treatment, indicating that H2S is required for ABA-mediated stomatal closure. The Arabidopsis mutant abi1 is impaired in ABA signalling and insensitive to H2S, suggesting that H2S is downstream ABA. Thus, data support that a connection between H2S and NO operates a fine regulation of gas exchange in plants resulting in a control of plant water status. Experiments are in progress to find experimentally H2S targets among the GC PM Ion channels. The richness of the redox chemistry of the different NO forms (NO.; NO and NO+) reacting with H2S (H+ and HS) in GCs is an intriguing puzzle to decipher ABA crosstalk with NO and H2S. To understand the redox regulation of GCs in different plant environmental scenarios is necessary to unveil how the physiology of GCs makes use of NO and H2S as intermediates in a signalling cascade leading to selective PM ion channels activation/inhibition.