Molecular characterization of three genes encoding crustin-like peptides in the Morotoge shrimp, Pandalopsis japonica

Abstract

Antimicrobial peptides (AMPs) play an important role in the innate immune system, and members of the cationic AMP family are widely distributed in both vertebrates and invertebrates. Penaeidins and crustins are most widely studied in decapod crustaceans. Penaeidins are cationic AMPs of 5？7 kDa, characterized by a proline-rich amino-terminal domain and a cysteine-rich carboxyl terminus domain. In present study, three putative crustin-like full-length cDNAs (Pj-crus Ia, Ib and IIa) were isolated from the Pandalid shrimp, Pandalopsis japonica and their gene organizations were also determined. The full-length cDNAs of Pj-crus Ia, Ib and IIa consisted of 1135, 580 and 700 nucleotides encoding a protein with 109, 119 and 186 amino acids residues, respectively. All three crustins isolated in this study contained a WAP domain at the C-terminus formed by eight conserved cysteine residues for four disulfide bridges. Phylogenetic analysis by WAP domains revealed that Pj-crus Is belong to carcinin, which is mostly identified from Brachyura and Astacidea. By contrast, Pj-crus IIa clustered with typical crustin which are mainly found in Dendrobranchiata. Based on the amino acid sequence similarities and domain organizations, the amino acid sequences of Pj-crus Ia, Ib and IIa showed that they belong to type I (Pj-crus Ia and Ib) and type II (Pj-crus IIa) crustin. Pj-crus Ia has four exons interrupted by three introns, whereas Pj-crus Ib and Pj-crus IIa have three exons. The expression profile data by end-point RT-PCR showed that three Pj-crus genes exhibit different tissue-distribution profiles. Pj-crus Ia was detected epithelia and brain and Pj-crus Ib was detected epithelia, brain and gill while Pj-crus IIa showed ubiquitous expression profile. This comparative study of putative crustacean AMPs will help us to extend our knowledge about the evolutional relationship and physiological roles of various arthropod AMPs.