The maturation profile triggers differential expression of sugar metabolism genes in melon fruits

Melons are commercially important crops that requires specific quality attributes for successful commercialization, including accumulation of sugars, particularly sucrose. This trait can be influenced by various factors, such as the type of ripening. Cucumis melo L. is an ideal species for studying sugar metabolism because it has both climacteric and non-climacteric cultivars. Thus, this study aimed to examine the gene expression of sucrose metabolism candidates using RT-qPCR, in conjunction with postharvest physiological analyzes and high-performance liquid chromatography-based sugar quantification, in the melon cultivars 'Gaúcho' (climacteric) and 'Eldorado' (non-climacteric). The results showed that sucrose synthase 1 played a role in the synthesis and accumulation of sucrose in both cultivars, whereas sucrose synthase 2 was more highly expressed in 'Gaúcho', contributing to lower hexose content. Invertase inhibitor 1 was more highly expressed in 'Eldorado' and may be involved in sugar-induced maturation. Neutral α-galactosidase had distinct functions, playing a role in substrate synthesis for the growth of young 'Eldorado' fruits, whereas in mature 'Gaúcho' fruits it participated in the metabolism of raffinose family oligosaccharides for sucrose accumulation. The expression of trehalose-6-phosphate synthase genes indicated a greater involvement of these enzymes in the sugar regulation in 'Gaúcho' melons. These findings shed light on the intraspecific differences related to fruit quality attributes in different types of maturation and contribute to a deeper understanding of the underlying molecular mechanisms involved in the metabolism of sugars in melons, which can inform breeding programs aimed at improving fruit quality attributes in this crop.