[Identification of the cucumber CsCYP90 gene and its effects on fruit sugar and polyphenol metabolism]

The metabolism and quality of cucumber (Cucumis sativus) fruits are modulated by various gene families. Nevertheless, the role of the cytochrome P450 family gene CsCYP90 in cucumber fruit quality remains largely unreported. To conduct an in-depth investigation into the specific function of the CsCYP90 gene in the formation of cucumber fruit quality and analyze its underlying metabolic regulatory mechanism, we cloned CsCYP90 (CsaV3_1G007770) from cucumber and discovered that it had the highest expression level in fruits. Phylogenetic analysis revealed a close evolutionary relationship with melon, placing it within the same CYP90 subclade. Transgenic vectors harboring CsCYP90 were constructed to generate overexpression lines, followed by metabolomic sequencing and physiological assays. Overexpression of CsCYP90 significantly altered the accumulation of various metabolites, including glutamine, adenosine monophosphate, and isomaltose, and enriched multiple biological pathways such as amino acid biosynthesis, pentose phosphate pathway, starch and sucrose metabolism, and phenylpropanoid biosynthesis. These changes result in elevated soluble sugar content and reduced tannin levels in transgenic fruits, improving the overall fruit quality. This study reveals the key role of the CsCYP90 gene in the metabolic regulation and quality formation of cucumber fruits, providing a novel gene target and theoretical basis for cucumber quality improvement.