Metabolic and Starch Biosynthetic Networks Underlying Yam Waxiness Formation Revealed by Integrated Transcriptomics and Proteomics

Waxiness, a key starch-related texture determining yam eating quality, remains poorly understood at the genetic and molecular levels, requiring further study for targeted quality improvement. Nine yam varieties with contrasting waxiness were analyzed using integrated transcriptomic and proteomic approaches to elucidate starch structure and metabolism. The results revealed that high-waxiness yam showed elevated expression of sucrose transport and starch precursor genes associated with higher starch content. Starch synthases (SSIII and SSIV) in yam regulated short and intermediate (6 < X ≤ 24) amylopectin chains. Starch branching enzyme (SBE), enriched in high-waxiness samples, catalyzed α-1,6 bond formation to promote long-chain amylopectin (36 < X ≤ 100) synthesis, thereby increasing starch molecular size and enhancing starch stability and rheology, contributing to waxiness formation. Upregulated GBSSII may contribute to a higher starch content in high-waxiness yam. These findings provide a mechanistic basis for waxiness and highlight key gene targets for improving the tuber texture quality.