Transcriptome profiling of mantle tissue reveals candidate genes associated with growth variation in Asian hard clam (Meretrix meretrix).

Growth rate is an important economic trait in the Asian hard clam Meretrix meretrix, yet the molecular basis underlying growth variation remains poorly understood. In this study, fast- and slow-growing individuals from the same breeding cohort and cultured under identical pond conditions were selected for comparative transcriptomic analysis of mantle tissue. Differential expression and functional enrichment analyses identified genes and biological pathways potentially associated with growth variation. The identified differentially expressed genes were mainly involved in muscle development, shell formation, extracellular matrix remodeling, biomineralization, energy metabolism, iron transport, and immune-related processes. Representative genes, including myosin heavy chain, chitinase3, cathepsin K, tyrosinase, carbohydrate sulfotransferase 11, pantetheinase-like protein, and hephaestin, showed distinct expression patterns between fast- and slow-growing clams and may contribute to differences in growth performance. Several representative genes were further validated by RT-qPCR, and the expression trends were generally consistent with the RNA-seq results. Overall, this study provides a mantle transcriptomic resource for M. meretrix and identifies candidate genes and pathways potentially associated with growth variation, providing useful molecular information for understanding growth regulation and future genetic improvement and selective breeding of this species.