Melão climatérico X não climatérico: diferencial de expressão gênica no metabolismo de açucares e carotenoides.

Abstract

Among the important quality attributes for the commercialization of melon fruits are the accumulation of sugars, mainly sucrose, and the flesh and rind color. Such traits can be affected, among other factors, by the type of ripening. The species Cucumis melo L. is of extreme interest for studies aimed at the metabolism of these compounds as it has both climacteric and nonclimacteric cultivars. Thus, this work aimed to investigate the gene expression of candidates for sucrose metabolism and carotenogenesis through RT-qPCR in an integrative approach to physiological analyzes of postharvest and sugar quantification through liquid chromatography of high performance, in melon fruits cv. Gaucho (climacteric) and cv. Eldorado (nonclimacteric). The results presented here indicate that sucrose synthase 1 (CmSUS1) has the function of synthesis and sucrose accumulation for both cultivars, while sucrose synthase 2 (CmSUS2) is higher expressed in 'Gaúcho' melon fruits, contributing to the lower content of hexoses in this cultivar. The invertase inhibitor 1 (CmINH1) is higher expressed in nonclimacteric fruits and may be involved in maturation triggered by sugars. Neutral αgalactosidase (CmNAG2) has distinct roles for the two cultivars, acting in the synthesis of substrates for the growth of young 'Eldorado' fruits, while in mature 'Gaúcho' fruits it participates in the metabolism of OFR for sucrose accumulation. The expression of trehalose6-phosphate synthase (TPS) genes indicates a greater participation of these enzymes in the regulation of sugars in 'Gaúcho' melon, except for the expression of CmTPS7, which also increases during the ripening of 'Eldorado'. In the carotenoid pathway, carotene isomerase 1 and 2 (CmCRTISO1 and CmCRTISO2) and β-ring carotene hydroxylase (CmβOHase1) are higher expressed in 'Gaúcho' melon fruits at premature and full ripening stages and may be involved in the formation of pigments, volatile compounds and phytohormones for this cultivar. These results contribute to the elucidation of intraspecific differences related to fruit quality attributes in different types of maturation and demonstrate for the first time the expression of genes participating in this process for the cultivar 'Gaúcho', of commercial importance for Brazil.