Cloning of PGRP Gene and Its Expression Responding to the Stimulations of Vibrio Alginolyticus, LPS, and Poly (I:C) in Pinctada fucata

Abstract The PfPGRP gene from the pearl oyster Pinctada fucata was cloned and expressed in different tissues with and without stimulation by Vibrio alginolyticus , LPS, and Poly (I:C) to investigate its role in the immune response. The cDNA sequence of PfPGRP was 789 bp long, containing an open reading frame of 591 bp that encoded 196 amino acids. Phylogenetic analysis showed that the genetic distance between vertebrate and invertebrate PGRPs was significant, and the homology of PGRP gene sequences in mollusks was around 50%. The PfPGRP gene had the highest homology with the PGRP gene from Crassostrea gigas , at 72.9%. Protein domain prediction identified a conserved canonical PGRP domain and an Ami_2 domain in PfPGRP , suggesting that it could hydrolyze invading bacteria and terminate the immune response. Quantitative PCR showed that PfPGRP was expressed constitutively in all tissues, with the highest levels in the mantle, followed by the gonad and hepatopancreas. The expression of PfPGRP in the mantle was significantly upregulated after LPS injection, indicating that this tissue is more sensitive to LPS and plays a crucial role in defending against bacterial invasions. Similarly, the expression of PfPGRP in the hepatopancreas was significantly upregulated after both Vibrio and LPS injections, but reached its maximum later in the Poly (I:C) group, suggesting that it is more sensitive to bacteria and may be involved in bacterial elimination.Overall, these results suggest that PfPGRP plays an essential role in the innate immune system of P. fucata and is involved in defense against bacterial and viral invasions.