Strigolactones are involved in hydrogen sulfide-enhanced salt tolerance in tomato seedlings

Strigolactones (SLs) and hydrogen sulfide (H2S) have both been shown to play important roles in plant growth, development, and environmental adaption. At present, there was no reported on the mechanism by which SLs might participate in H2S-induced salt tolerance. In this study, tomato (Solanum lycopersicum L. ‘Micro-Tom’) was used to investigate the role of SLs and H2S and their relationship under salt stress. Our results show that 25 µM H2S donor sodium hydrosulfide (NaHS) and 15 µM SLs synthetic analogue GR24 significantly promoted tomato seedling growth under salt stress. TIS108 (3 µM, a SLs synthesis inhibitor) and hypotaurine (HT, 300 µM, a H2S scavenger) inhibited the positive role of NaHS and GR24 under salt stress, respectively. Meanwhile, NaHS treatment significantly increased endogenous SL content, the activity of SL synthesis-related enzymes CCD7 and CCD8, and the expression of SL synthesis-related genes (SlD27, SlD14, SlMAX1, and SlMAX2) under salt stress. Further, after silencing a SL synthesis-related gene SlD27, the relieving role of NaHS in salt stress was basically eliminated. Silencing of SlD27 decreased endogenous SL content, while NaHS did not enhance the endogenous SL content in SlD27-silencing seedling. Therefore, H2S might enhance salt tolerance in tomato seedlings by up-regulating the expression of SL synthesis-related gene SlD27.