LysM-containing proteins function in the resistance of Litopenaeus vannamei against Vibrio parahaemolyticus infection.

Lysin motif (LysM) is a functional domain that can bind to peptidoglycans, chitin and their derivatives. The LysM-containing proteins participate in multiple biological processes, such as the hydrolysis of bacterial cell walls and the perception of PAMPs in plants and high animals. In the present study, two genes encoding LysM-containing proteins, designated as LvLysM1 and LvLysM2, were identified in the Pacific white shrimp, Litopenaeus vannamei, and their functions during Vibrio infection were analyzed. The open-reading frame (ORF) of LvLysM1 was 795 bp, only encoding a LysM domain at the N-terminal region. The ORF of LvLysM2 was 834 bp, encoding a LysM domain at the central region and a transmembrane region at the C-terminal region. Both LvLysM1 and LvLysM2 were widely transcribed in all tested shrimp tissues. Enzyme-linked immunosorbent assay (ELISA) showed that the recombinant protein of LvLysM2 could bind to different bacterial polysaccharides, while LvLysM1 showed no direct binding activity. The transcripts of LvLysMs in gills increased significantly after infection with Vibrio parahaemolyticus. When LvLysM1 or LvLysM2 was knocked down by dsRNA, the mortality of shrimp was significantly increased after infection with Vibrio parahaemolyticus. Interestingly, some SNPs existed in these two genes were apparently correlated with the Vp resistance of shrimp. These results suggested that LvLysM1 and LvLysM2 might contribute to the disease resistance of shrimp. The data provide new knowledge about the function of LysM-containing proteins in shrimp and potential genetic markers for disease resistance breeding.