S-nitrosylation of GSNOR and LCD facilitates cadmium-induced programmed cell death in tomato seedlings.

Nitric oxide (NO) and hydrogen sulphide (H2S) perform multiple regulatory functions in plants; however, the molecular mechanisms underlying NO and H2S interaction remain poorly understood. In this study, we aim to analyse the function of S-nitrosoglutathione reductase (GSNOR) and L-cysteine desulfhydrase (LCD) in the programmed cell death (PCD) response to cadmium (Cd2+) stress using GSNOR and LCD knockout and overexpressing transgenic tomato (Solanum lycopersicum). Our results confirmed that GSNOR, an enzyme that mediates NO dynamic equilibrium, and LCD, an enzyme involved in H2S generation, inhibit Cd2+ stress-induced PCD in tomato plants. GSNOR and LCD knockout plants were sensitive to Cd2+ and exhibited increased cell death compared to the controls. S-nitrosylation of GSNOR at Cys47 and LCD at Cys225 changed their subcellular localisation and decreased GSNOR and LCD activity, thereby increasing Cd2+ uptake and promoting PCD. Thus, S-nitrosylation attenuates the interaction between GSNOR and LCD during PCD. In conclusion, GSNOR and LCD are involved in the response to Cd2+ stress, and their interactions and S-nitrosylation play critical roles in NO- and H2S-induced Cd2+ stress responses.