Unraveling the molecular mechanisms of melon fruit firmness: insights into cell wall gene expression and regulation

Melons exhibit broad phenotypic variation, with fruits undergoing both climacteric and non-climacteric maturation patterns that directly impact the texture of the endocarp. The loss of fruit firmness is intricately linked to the degradation of cell wall components, mainly cellulose, hemicelluloses, and pectins. The cell wall serves multiple functions, including providing mechanical resistance, regulating osmotic pressure, acting as a diffusion barrier, controlling cell adhesion and expansion, and protecting the plasma membrane from damage and pathogens. The biochemical changes influencing the physical properties of the wall are orchestrated by gene expression and interactions with epigenetic and hormonal factors. Establishing knowledge of these interactions and understanding the structural changes that occur during maturation are essential for elucidating the primary causes of firmness loss in melon fruits. In this review we summarize knowledge on the expression of cell wall genes in melon and how they contribute to the synthesis, loosening, and depolymerization of the cell wall during maturation. Such information provides a valuable foundation for advanced postharvest management strategies and future physiological and molecular studies to enhance fruit quality and extend shelf life.