Integrated application of transcriptomics and metabolomics provides insights into condition index difference mechanisms in the Pacific oyster (Crassostrea gigas).

The condition index (CI) is an economically important tool for assessing the quality of oysters, such as the Pacific oyster Crassostrea gigas. However, little is known about the mechanisms that underlie differences in CI between different C. gigas populations. In this study, we integrated transcriptomic and metabolomic profiling to investigate the mechanisms that underlie the differences between high- and low-CI groups in one- and two-year-old populations of C. gigas. The results indicate that differences in CI were associated with the regulation of growth-related genes, the FoxO signaling pathway, and the complex regulation of carbohydrate, lipid, amino acid, and energy metabolism. Moreover, the mechanisms underlying these differences differed between the populations. This study is the first to elucidate the molecular and chemical mechanisms associated with CI, and the results will be helpful for breeding higher quality oysters.