RNAi Identified the Potential Functions of Actin-like Protein in the Growth Performance of Macrobrachium nipponense.

Macrobrachium nipponense is an important commercial freshwater prawn species in China. Since larger individuals command higher market value, there is a pressing need to identify growth-related genes and single-nucleotide polymorphisms (SNPs) to facilitate genetic improvement in this species. Previous studies have suggested a potentially regulatory role of an actin-like protein (ACTL) in the growth of M. nipponense. Therefore, the present study aimed to functionally characterize the role of ACTL in growth and identify growth-associated SNPs within this gene. The open reading frame of Mn-ACTL is 1131 bp, encoding a protein with 377 amino acids. Blastx and phylogenetic analyses indicated that Mn-ACTL shares a close evolutionary relationship with orthologs from Macrobrachium rosenbergii and Palaemon carinicauda. The highest expression level of Mn-ACTL in muscle tissue detected by qPCR suggested its potential involvement in growth regulation. RNA interference experiments showed that prawns injected with dsGFP exhibited larger body sizes than those injected with dsACTL, indicating that knockdown of Mn-ACTL expression inhibits growth performance in M. nipponense. Furthermore, muscle tissue from the dsACTL-injected group displayed looser myofibril packing, visibly eroded areas, and increased sarcomere spacing. Collectively, these results demonstrated that ACTL positively regulates growth in M. nipponense. Additionally, the T allele at locus S28_17149891 and the G allele at locus S28_17145758 were significantly associated with growth traits (p < 0.05). In conclusion, this study confirmed the positive regulatory role of ACTL in growth and identified growth-associated SNPs in M. nipponense, providing valuable insights for breeding new varieties with enhanced growth performance in this species.