MaBRG3-Mediated Ubiquitin-Dependent Degradation of the Transcriptional Repressor MaC3H33-like Promotes Ethylene-Induced Banana Fruit Softening

Ethylene-dependent softening is a crucial physiological process that influences the postharvest quality of banana fruit, with cell wall disassembly playing a key role in firmness loss. While the functions of several ripening-associated cell wall-modifying genes have been characterized, the regulatory mechanisms governing their expression are still mostly unknown. This study identified a transcriptional repressor, MaC3H33-like, which directly interacts with and suppresses the promoter of <i>MaEXP1</i>, an important cell wall-modifying gene involved in banana fruit softening. Moreover, MaC3H33-like interacts directly with a BOI-class E3 ubiquitin ligase, MaBRG3. Notably, MaBRG3 ubiquitinates MaC3H33-like to mediate ubiquitin-dependent degradation, thereby allowing the expression of <i>MaEXP1</i> that promotes the fruit softening process. Collectively, these findings suggest that ethylene induces banana fruit softening presumably through the ubiquitin-dependent degradation of MaC3H33-like by MaBRG3, resulting in the activation of <i>MaEXP1</i> gene expression and ultimately the softening of banana fruit. This study provides potential targets for the development of postharvest preservation technologies.