<i>S</i> ‐nitrosylation of <scp>GSNOR</scp> and <scp>LCD</scp> facilitates cadmium‐induced programmed cell death in tomato seedlings

Summary Nitric oxide (NO) and hydrogen sulphide (H 2 S) perform multiple regulatory functions in plants; however, the molecular mechanisms underlying NO and H 2 S 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 (Cd 2+ ) 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 H 2 S generation, inhibit Cd 2+ stress‐induced PCD in tomato plants. GSNOR and LCD knockout plants were sensitive to Cd 2+ 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 Cd 2+ 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 Cd 2+ stress, and their interactions and S ‐nitrosylation play critical roles in NO‐ and H 2 S‐induced Cd 2+ stress responses.