Multi-scale structural and functional enhancement of starch in sweet potato anthocyanin biosynthesis-deficient mutant: Insights into mechanisms and food applications

The relationship between anthocyanins and starch biosynthesis in sweet potato root tubers is not well understood, primarily due to the genetic complexity of hexaploid genomes and the scarcity of appropriate genetic materials. To fill this knowledge gap, the purple-fleshed sweet potato cultivars Ningzishu 4 and Ningzishu 1, along with their naturally occurring anthocyanin-deficient yellow-fleshed mutant were employed for comparative analyzes while eliminating interference from genotypic background variations. In the mutant, the levels of soluble sugars, starch, amylose, and amylopectin A and B3+ chains increased, although starch morphology and crystalline type remained unaffected. Alternatively, the granule size, relative crystallinity, and lamellar peak intensity decreased. These changes can be attributed to the differential expression levels of starch biosynthesis related genes. Furthermore, the starches in the mutant displayed modified gelatinization, viscosity, and digestion characteristics. This study established a metabolic connection between anthocyanin and starch metabolism using natural mutants, offering insights for enhancing sweet potato quality traits and developing functional starch varieties via targeted breeding approaches.