SlDCD and SlLCD increased the salt tolerance in tomato seedlings by enhancing antioxidant and photosynthesis capacity.

Using gene silence and heterologously overexpression, hydrogen sulfide synthesis-related genes l-cysteine desulfhydrase and d-cysteine desulfhydrase have been shown to enhance salt tolerance in tomato seedlings. Hydrogen sulfide (HS) plays an important role in alleviating abiotic stress. L-Cysteine desulfhydrase (LCD) and D-cysteine desulfhydrase (DCD) are two important HS synthesis enzymes. Until now, whether and how SlDCD and SlLCD increase salt tolerance in plant are still unknown. Here, we explored the effects of SlDCD and SlLCD on salt tolerance in tomato seedlings by silencing SlDCD and SlLCD and heterologously overexpressing SlDCD and SlLCD. In tomato seedlings, exogenous sodium hydrosulfide (NaHS, a HS donor) increased salt tolerance while decreasing HS synthesis-related enzyme activity, endogenous HS levels, and HS synthesis-related gene expression. Silencing SlDCD and SlLCD inhibited tomato seedling growth under salt stress, increased relative conductivity, MDA, HO, O, Pro, and carotenoid content, Ci and NPQ. In contrast, it decreased the activity of antioxidant enzymes (POD, SOD, CAT and APX) and the expression of related genes (POD, SOD, CAT and APX), chlorophyll content, photosynthetic parameters (Pn, Gs and Tr) and fluorescence parameters (Fv/Fm, φPSII and qP), while exogenous NaHS considerably mitigated the adverse impacts of salt stress in SlDCD and SlLCD silenced-tomato seedlings. Overexpression of SlDCD and SlLCD in Arabidopsis significantly enhanced plant salt tolerance. Taken together, our results indicate that SlDCD and SlLCD could enhance the antioxidant activity and photosynthesis capacity under salt stress, which results improving salt tolerance in tomato seedlings.