Genome-wide identification of crustacyanin and function analysis of one isoform high-expression in carapace from Neocaridina denticulata sinensis.

Lipocalin proteins transport hydrophobic molecules, including apolipoprotein D, retinol-binding protein, and crustacyanin (CRCN). CRCN can combine with astaxanthin to cause a bathochromic shift in the emission spectrum of astaxanthin from red to blue. Therefore, CRCN influences the colors and patterns of crustaceans, which are important for various biological functions such as camouflage, reproduction, and communication. For aquatic organisms, body color is economically important and can be indicative of habitat water quality. In this study, thirteen CRCN genes (NdCRCNs) were first discovered in Neocaridina denticulata sinensis, contradicting prior findings of a few isoform genes in a species. The expression pattern of NdCRCNs in tissues showed that the expression of one CRCN isoform gene, named NdCRCN-30, was the highest in the carapace. In situ hybridization (ISH) analysis revealed that NdCRCN-30 was predominantly distributed in the outer epidermis of shrimp. Interference of NdCRCN-30 could cause a change in the color of the carapace. RNA-seq was performed after knockdown with the NdCRCN-30, and differential gene enrichment analysis revealed that this gene is primarily associated with antioxidant function, pigmentation, and molting. Overall, our results will provide new insights into the biological function of the CRCN and genetic breeding for changing body color in economic crustaceans.