Ploidy-associated glycogen differences in Crassostrea gigas: Insights from the glycogen-metabolism effector layer

Ploidy variation influences growth, reproduction, and nutritional traits in oysters, but its relationship with glycogen accumulation remains poorly understood. Here, diploid, triploid, and tetraploid Crassostrea gigas were comparatively investigated using glycogen content determination, glycogen synthase activity assays, mRNA transcriptomics, miRNA sequencing, and lncRNA profiling. Oysters with different ploidy levels showed significant differences in glycogen content and glycogen synthase activity, accompanied by marked variation in genes and pathways involved in carbon metabolism, glycolysis/gluconeogenesis, starch and sucrose metabolism, and glycogen metabolism. Trend analysis identified co-expression modules associated with ploidy-dependent glycogen variation. Key glycogen metabolism-related genes, including Hex-t2, Glys, GBE1, and PYGM, displayed distinct expression patterns among ploidy groups. Moreover, differentially expressed miRNAs showed extensive potential regulatory relationships with glycogen metabolism-related genes, while lncRNA-associated ceRNA networks suggested additional regulatory involvement in carbohydrate metabolism. These results indicate that glycogen differences among oysters with different ploidy levels are associated with coordinated shifts in the glycogen-metabolism effector layer. This study provides insight into the molecular basis of ploidy-associated glycogen regulation in oysters and offers a theoretical reference for germplasm improvement and quality breeding.