Hydrogen sulfide interacts with calcium signaling to enhance the chromium tolerance in Setaria italica

The oscillation of intracellular calcium (Ca2+) concentration is a primary event in numerous biological processes in plants, including stress response. Hydrogen sulfide (H2S), an emerging gasotransmitter, was found to have positive effects in plants responding to chromium (Cr6+) stress through interacting with Ca2+ signaling. While Ca2+ resemblances H2S in mediating biotic and abiotic stresses, crosstalk between the two pathways remains unclear. In this study, Ca2+ signaling interacted with H2S to produce a complex physiological response, which enhanced the Cr6+ tolerance in foxtail millet (Setaria italica). Results indicate that Cr6+ stress activated endogenous H2S synthesis as well as Ca2+ signaling. Moreover, toxic symptoms caused by Cr6+ stress were strongly moderated by 50 mu M H2S and 20 mM Ca2+. Conversely, treatments with H2S synthesis inhibitor and Ca2+ chelators prior to Cr6+-exposure aggravated these toxic symptoms. Interestingly, Ca2+ upregulated expression of two important factors in metal metabolism, MT3A and PCS, which participated in the biosynthesis of heavy metal chelators, in a H2S-dependent manner to cope with Cr6+ stress. These findings also suggest that the H2S dependent pathway is a component of the Ca2+ activating antioxidant system and H2S partially contributes Ca2+-activating antioxidant system. (C) 2014 Elsevier Ltd. All rights reserved.