Genome-wide identification and comparative analysis of Leucine-Rich Repeat Containing (LRRC) gene and their expression responses to Vibrio alginolyticus infection in the Manila clam (Ruditapes philippinarum)

Leucine-rich repeat (LRR) domains are important components of many pattern recognition receptors (PRRs). Previous studies have demonstrated that LRR domain-containing immune receptors, such as nucleotide-binding oligomerization domain-like receptors (NLRs) and Toll-like receptors (TLRs), play important roles in innate immunity in aquatic animals. In addition to these well-characterized LRR-containing receptors, also possesses a group of LRR-containing proteins. These proteins were collectively referred to as leucine-rich repeat-containing (LRRC) proteins in this study, and their genomic characteristics, evolutionary relationships, were systematically analyzed. In this study, a genome-wide identification and characterization of LRRC genes were performed in the Manila clam. A total of 97 unclassified LRR genes were identified and designated as RpLRRCs.. Expression profiling indicated that RpLRRCs are predominantly expressed in the labial palps, digestive gland, and gills, increasing from the blastula stage and peaking at the juvenile stage during development, based on the transcriptome results from V. alginolyticus, V. anguillarum and V. parahaemolyticus, some RpLRRCs were involved in the response to different Vibrio stress. The qPCR analysis following V. alginolyticus challenge demonstrated that different RpLRRC members exhibit diverse response patterns to Vibrio infection. These results suggest that RpLRRCs may play critical roles in immune regulation. The RpLRRC gene family exhibits diverse structural characteristics and regulatory mechanisms and likely plays important roles in the growth, development, and immune response of R. philippinarum.