Integrated physiological, biochemical and transcriptomic analyses revealed key genes regulating ascorbic acid biosynthesis during sweet potato development

Sweet potato (<i>Ipomoea batatas</i> Lam.) is a globally important food crop with higher ascorbic acid (AsA) content than most staple crops. However, the regulatory mechanisms of AsA accumulation in sweet potato remain unclear. In this study, we systematically examined the regulatory network of AsA metabolism by integrating physiological and biochemical analyses with transcriptome sequencing in four representative varieties. The results revealed significant variation in AsA accumulation during root development, ranging from 10.96 to 36.45 mg/100 g FW. Metabolic pathway analysis showed that AsA biosynthesis is mainly regulated through the L-galactose pathway, involving the genes <i>HK</i>, <i>PMI</i>, <i>PMM</i>, <i>GME</i>, and <i>GalLDH</i>, and the myo-inositol pathway represented by <i>MIOX</i>. Weighted gene co-expression network analysis (WGCNA) further identified <i>MIOX</i> as a highly connected hub gene within the AsA-associated network module. These findings provide important insights into the molecular basis of AsA metabolism in sweet potato and highlight promising candidate genes for future functional validation and molecular breeding efforts aimed at enhancing nutritional quality.