A Peritrophin-44 gene in Litopenaeus vannamei is involved in disease resistance.

Peritrophic membrane (PM) is a pellicle structure present in the midgut of some invertebrates, such as insects and crustaceans. It could isolate harmful components and pathogens in food from intestinal epithelial cells; and it also plays a role in improving digestion and absorption efficiency. So PM is important for survival of its owner. In current study, 44 PM proteins were identified in Litopenaeus vannamei by PM proteome analysis. Among these PM proteins, the Peritrophin-44 homologous protein (LvPT44) was further studied. Chitin-binding assay indicated that LvPT44 could bind to colloidal chitin, and immunoeletron microscopy analysis shown that it was located to PM of L. vannamei. Furthermore, LvPT44 promoter was found to be activated by L. vannamei STAT and c-Jun. Besides, LvPT44 was induced by ER-stress as well as white spot syndrome virus infection. Knocked-down expression of LvPT44 by RNA inference increased the cumulative mortality of shrimp that caused by ER-stress or white spot syndrome virus. These results suggested that LvPT44 has an important role in disease resistance.

Study of the antivirus function mediated by STING in Micropterus salmoides.

Stimulator of interferon genes (STING) has been demonstrated as a critical mediator in the innate immune response to cytosolic DNA and RNA derived from different pathogens. While the role of Micropterus salmoides STING (MsSTING) in largemouth bass virus is still unknown. In this study, RT-qPCR assay and Western-blot assay showed that the expression levels of MsSTING and its downstream genes were up-regulated after LMBV infection. Pull down experiment proved that a small peptide called Fusion peptide (FP) that previously reported to target to marine and human STING as a selective inhibitor also interacted with MsSTING in vitro. Comparing with the RNA-seq of Largemouth bass infected with LMBV singly, 326 genes were significantly up-regulated and 379 genes were significantly down-regulated in the FP plus LMBV group in which Largemouth bass was treatment with FP before LMBV-challenged. KEGG analysis indicated that the differentially expressed genes (DEGs) were mainly related to signaling transduction, infectious disease viral, immune system and endocrine system. Besides, the survival rate of LMBV-infected largemouth bass was highly decreased following FP treatment. Taken together, our study showed that MsSTING played an important role in immune response against LMBV infection.