Transcriptome profiling and in silico detection of the antimicrobial peptides of red king crab Paralithodes camtschaticus

Endogenous antimicrobial peptides (AMPs) are evolutionarily ancient factors of innate immunity, which are produced by all multicellular organisms and play a key role in their protection against infection. Red king crab (Paralithodes camtschaticus), also called Kamchatka crab, is widely distributed and the best known species of all king crabs belonging to the family Lithodidae. Despite their economic importance, the genetic resources of king crabs are scarcely known and no full-genome sequences are available to date. Therefore, analysis of the red king crab transcriptome and identification and characterization of its AMPs could potentially contribute to the development of novel antimicrobial drug candidates when antibiotic resistance has become a global health threat. In this study, we sequenced the P. camtschaticus transcriptomes from carapace, tail flap and leg tissues using an Illumina NGS platform. Libraries were systematically analyzed for gene expression profiles along with AMP prediction. By an in silico approach using public databases we defined 49 cDNAs encoding for AMP candidates belonging to diverse families and functional classes, including buforins, crustins, paralithocins, and ALFs (anti-lipopolysaccharide factors). We analyzed expression patterns of 27 AMP genes. The highest expression was found for Paralithocin 1 and Crustin 3, with more than 8,000 reads. Other paralithocins, ALFs, crustins and ubiquicidins were among medium expressed genes. This transcriptome data set and AMPs provide a solid baseline for further functional analysis in P. camtschaticus. Results from the current study contribute also to the future application of red king crab as a bio-resource in addition to its being a known seafood delicacy.