Characterization of secreted proteins and chitinase diversity in hepatopancreas of Panulirus homarus based on full-length transcriptome analysis

The secretory function of the hepatopancreas plays a central role in key physiological processes related to aquaculture in crustaceans, including digestion, molting, and immunity. However, studies on the hepatopancreatic secretory function of the Scalloped spiny lobster (Panulirus homarus) remain scarce, which to some extent has constrained advances in its culture techniques. To systematically analyze the secretory functions of P. homarus hepatopancreas and elucidate the formation mechanisms and characteristics of its chitinase family, based on full-length transcriptome sequencing combined with signal peptide prediction, we systematically analyzed the secretory function of the hepatopancreas and conducted an in-depth investigation into the formation mechanism and characteristics of the chitinase family, which exhibited the highest diversity. A total of 9 163 unigenes were obtained, among which 7 838, 6 432, 5 072, 6 787, and 7 021 unigenes were annotated in the NR, GO, KEGG, eggNOG, and Swiss-Prot databases, respectively. The results indicate that the secreted proteins of P. homarus hepatopancreas are primarily involved in typical secretory functional pathways such as signal transduction, signaling molecules and interaction, digestive system, immune system, endocrine system, and various nutritional metabolic processes. The largest number of secretory proteins was obtained during the identification of metabolic pathways, and a total of 21 Class I, and 6 Class II and III chitinases transcripts were ultimately identified. Analysis of the chitinases shows that the variations mainly localised after the 350 position in the protein sequence. This study provides a theoretical foundation for functional research on hepatopancreatic secretion in P. homarus, and supports the development of its aquaculture technologies in areas such as feed formulation, immune regulation, disease prevention, and molting control.