Several pattern recognition receptors (PRRs) involved in innate immunity have been identified and characterized in earthworms. Peptidoglycan recognition proteins (PGRPs) are highly conserved PRRs that activate effector pathways such as prophenoloxidase cascade and Toll-like receptor pathway. In addition, PGRPs function as an enzyme, N-acetylmuramoyl-l-alanine amidase (NAMLAA), to directly hydrolyze peptidoglycan. We identified four full-length complementary DNA (cDNA) sequences, Ean-PGRP1/2/3/4, in Eisenia andrei, an earthworm. Sequence and phylogenetic analyses indicate that earthworm PGRP orthologs resemble short PGRP member proteins. The subcellular localizations of four Ean-PGRPs lacking the transmembrane domain are predicted to be extracellular or cytoplasmic. All Ean-PGRPs contain a highly conserved PGRP domain with a conserved Zn
