MYB15 regulates fruit ripening by interacting with RIN to repress ethylene biosynthesis genes in tomato

For climacteric fruits, ethylene plays a key role in fruit ripening. The biosynthesis of ethylene is finely regulated by a complex network of positive and negative regulators. In previous studies, significant progress has been made on the positive regulators of ethylene biosynthesis, but the mechanisms of negative regulators are still unclear. In this study, we found that the expression level of SlMYB15 is gradually decreased during the ripening process. SlMYB15 knock out accelerated the onset of fruit ripening and increased ethylene synthesis. SlMYB15 repress ethylene biosynthesis genes by directly binding to their promoters. Moreover, SlMYB15 physically interacts with key fruit ripening transcription factor Ripening Inhibitor (RIN), antagonistically modulating the expression of downstream ethylene biosynthesis genes to control the ripening process. Genetic interaction analyses showed that loss of SlMYB15 function partially rescues the non-ripening phenotype of rin mutants. Taken together, our findings uncover SlMYB15 as a transcriptional repressor that negatively regulates tomato fruit ripening and elucidate its underlying molecular mechanism, providing a foundation for precision breeding strategies aimed at modulating designed to mediate fruit ripening in tomato.