A jasmonate-responsive glutathione S-transferase gene SlGSTU24 mitigates cold-induced oxidative stress in tomato plants

Cold stress inhibits growth, reduces productivity and deteriorates fruit quality in tomato (Solanum lycopersicum). It is thus of critical importance to elucidate the mechanisms by which tomato plants respond to cold stress. Jasmonates (JAs) are a group of phytohormones crucial for plant growth, development and stress responses. However, the role of JA and the mode of actions in the cold response in tomato plants remain largely unknown. Here, we report a JA-responsive glutathione S-transferase gene SlGSTU24 that functions to alleviate cold stress in tomato. We found that SlGSTU24 was ubiquitously expressed in all examined tissues and was responsive to both JA and cold stress. Knockdown of SlGSTU24 via an approach of VIGS (virus-induced gene silencing) aggravated cold-induced damages, as evidenced by enhanced ROS (Reactive Oxygen Species) accumulation, MDA (malondialdehyde) content and electrolyte leakage. Application of MeJA prominently increased the expression of SlGSTU24, with concomitant decreases in MDA content as well as electrolyte leakage in tomato leaves under cold conditions. In contrast, blocking JA biosynthesis using DIECA dramatically suppressed the expression of SlGSTU24 and elevated MDA content and electrolyte leakage. Furthermore, JA-regulated SlGSTU24 expression was dependent on SlMYC2, a crucial regulator of JA signaling pathway. Knockdown of SlMYC2 profoundly decreased the expression of SlGSTU24, accompanied by enhanced MDA content and electrolyte leakage under cold conditions. Dual-luciferase assay showed that SlMYC2 activates the expression of SlGSTU24 in tobacco leaves. Collectively, these results support that JA-upregulated SlGSTU24 attenuates cold-induced oxidative stress in tomato. This study uncovers a crucial module MYC2-SlGSTU24 that maintains ROS homeostasis in tomato under cold conditions.