Characterization of a gill-abundant crustin with microbiota modulating function in Litopenaeus vannamei

Gills as the respiratory tissue of crustacean encounter various threats in the environment. The immune defense in gills is essential to the health of shrimp. In the present study, we identified a novel gill-abundant crustin, LvCrustin Ⅱ-1, from the shrimp Litopenaeus vannamei. The full-length open reading frame of LvCrustin Ⅱ-1 is 522 bp, which encodes 173 amino acid residues. The amino acid sequence of LvCrustin Ⅱ-1 contained a signal peptide, a glycine rich region, a cysteine rich region and a whey acidic protein (WAP) domain. The expression level of LvCrustin Ⅱ-1 was significantly up-regulated at different time points after Vibrio parahaemolyticus immersion. When LvCrustin Ⅱ-1 was silenced by dsRNA interference, the count of bacteria colonies increased significantly in the hepatopancreas of shrimp after V. parahaemolyticus immersion, which indicated that the infection progress of pathogenic bacteria was accelerated after LvCrustin Ⅱ-1 knockdown. Compared with the microbiota of seawater, the lower proportion of aquatic bacteria and higher proportion of symbiont in the gills microbiota of shrimp indicated the bacterial colonization was modulated by the host. Knockdown of LvCrustin Ⅱ-1 changed the proportion of some potential pathogens and aquatic bacteria, which supported the idea that the new identified crustin in the gills played important roles in modulation of the microbiota community in shrimp. The present data provided new insights into the multiple functions of crustin in the immunity of shrimp.