SlMsrB5-SlGRAS4 involved in methyl jasmonate-mediated ripening and quality of postharvest tomato fruit

Methionine (Met) sulfoxide reductase (Msr) is a protein that converts free or protein-bound Met sulfoxide (MetSO) to Met in horticultural crops, thereby facilitating protein repair. In our previous study, we identified SlMsrB5 as a significant up-regulated gene in response to methyl jasmonate (MeJA) treatment. Many studies have shown that MeJA not only induces ethylene production and promotes ripening but also improves the postharvest quality of horticultural crops. However, the specific function and mechanisms of SlMsrB5 in MeJA-regulated postharvest fruit ripening and quality remain unclear. In this work, we analyzed the effect of SlMsrB5 -s on the ripening and physiological quality of postharvest tomato fruit ( Solanum lycopersicum L.cv Jiaxina) treated with 0.05 mmol L -1 MeJA, which resulted in decreased fruit quality, and inhibited ethylene synthesis pathway. Through yeast two-hybrid (Y2H) screening and subsequent validation assays, we identified an interaction between SlMsrB5 and a member of the GRAS transcription factor family, namely SlGRAS4. Furthermore, oxidative treatment with 1 mmol L -1 hydrogen peroxide was shown to damage the protein structure of SlGRAS4 and its capacity to bind DNA, as demonstrated by protein migration tests and gel shift assays. However, the interaction between SlMsrB5 and SlGRAS4 partially restored the structure of SlGRAS4 and its ability to bind to DNA. SlGRAS4 is recognized to play a critical role in the ethylene biosynthesis regulation and stress responses in tomato fruit. Thus, current findings demonstrate the participation of SlMsrB5 in modulating postharvest tomato fruit ripening and quality by regulating the oxidation-reduction status of SlGRAS4. These findings shed light on the function and potential mechanisms of SlMsrB5 in the MeJA-mediated regulation of postharvest tomato fruit ripening and quality, contributing to our understanding of the underlying mechanisms that govern impact of MeJA on postharvest fruit quality.