The “Ataulfo” mango (Mangifera indica L.) maintains its L- ascorbic acid content during fruit ripening: Insights into synthesis and recycling pathways

Mango is consumed worldwide for its sweet flavor, pleasant aroma, high commercial value, and rich source of L-ascorbic acid (AA), an essential human micronutrient. AA is primarily synthesized in plants via the Smirnoff-Wheeler (SW) pathway. Alternative routes for AA synthesis, such as gulose, myo-inositol, and galacturonic acid, are proposed in some species alongside a recycling pathway that helps maintain AA homeostasis in plant cells. However, a formal genetic demonstration of the alternative routes for AA synthesis and recycling in mangoes remains. In this study, 165 genes associated with AA metabolism were identified in the “Tommy Atkins” mango genome; some of them were previously identified in mango “Ataulfo” and “Kent” transcriptomes. Physical-chemical parameters, AA content, and carbohydrate levels were measured in collected “Ataulfo” mangoes. The expression of SW key genes involved in AA synthesis from alternative and recycling pathways, was evaluated during postharvest ripening, and promoter regions of these genes were analyzed in silico for the presence of regulatory cis-elements. During ripening, transcript accumulation of MiGME-3, MiGGP-1, MiGalLDH, MiGALUR-1, MiPME-1, MIMDHAR-4, and MiAPX-4 from the SW, alternative and recycling pathways showed a significant increase of 3- to 10-fold. However, AA content remained relatively stable throughout ripening, averaging 124 mg/100 g fresh weight, suggesting additional regulatory factors that may counterbalance the increased synthesis. Promoter analysis revealed the presence of seven cis-elements associated with stress and ripening regulation, indicating potential regulatory mechanisms for the identified genes. More than one route could be active in mango fruits, contributing to AA biosynthesis and maintenance during ripening.