Hydrogen sulfide enhances Cd tolerance through persulfidation of SlGSTU24 in Solanum lycopersicum L

Aims Hydrogen sulfide (H₂S), a gaseous signaling molecule, plays a pivotal role in facilitating plant resistance to cadmium (Cd) stress. Glutathione S-transferases (GSTs) are critical enzymes to tolerate Cd stress in plants. However, the regulatory interplay between H₂S and GSTs activity remains elusive. Here, we identified the persulfidation of SlGSTU24 as a previously uncharacterized mechanism regulating Cd detoxification. Methods To investigate the effect of H₂S on the growth of tomato seedlings under Cd stress, 1, 3, and 5 mg/L CdCl 2 and 200 μM NaHS (an H₂S donor) were used to treat three-week-old seedlings for 7 days in this study. Morphological characteristics, malondialdehyde (MDA) content, non-protein thiol (NPT) levels, metallothioneins (MTs) and protein content of treated seedlings were analyzed. GSTs activity were assessed, and persulfidation proteomics was conducted on GSTs. Mass spectrometry and the modified biotin switch method (MBSM) identified persulfidated residues in SlGSTU24. Cys132 was mutated to alanine for functional analysis. Results Cd exposure inhibited the growth of tomato seedlings, while treatment with NaHS alleviated growth inhibition, decreased malondialdehyde (MDA) content and electrolyte leakage (EL) under Cd stress. The application of NaHS increased non-protein thiols glutathione (GSH) and phytochelatins (PCs) contents, and protein thiols metallothionein (MTs) content. The endogenous activity of GSTs was enhanced by NaHS. Cys132 in SlGSTU24 was identified as a persulfidated residue. Persulfidation of Cys132 increased the SlGSTU24 wild type (WT) activity. When Cys132 was mutated to alanine, H₂S-induced SlGSTU24 activity were compromised in SlGSTU24 Cys(C)132 Ala(A) . Conclusions H₂S-mediated persulfidation of Cys132 in SlGSTU24 enhances its activity and improves tomato resistance to Cd stress.