Shedding Light on the Antimicrobial Peptide Arsenal of Terrestrial Isopods: Focus on Armadillidins, a New Crustacean AMP Family

Abstract

In crustaceans, antimicrobial peptides (AMPs) are clustered into four major groups according to their amino acid composition and structure: (1) single-domain peptides containing cysteine residues such as anti-lipopolysaccharide-factor (ALF), (2) multi-domain or chimeric AMPs such as crustins, (3) non-conventional AMPs, and (4) linear single-domain AMPs. The majority of AMPs has been described in commercially exploited crustaceans, particularly decapods living in aquatic environments (crab, shrimp, lobster, and crayfish). Here, we aimed at establishing the AMPs repertoire of terrestrial isopods (Oniscidea), an original suborder of crustaceans adapted to life outside of the aquatic environment. Using transcriptomic data from 21 species, we identified 110 ALF and 73 crustin sequences. We also characterized the full-length sequence of armadillidins from 17 species, similar to the AMP previously described in the terrestrial isopod Armadillidium vulgare. Furthermore, we tested the antimicrobial activity of three armadillidin peptides characterized from three distantly related species. This analysis revealed similar activity spectra against pathogens, despite extensive structural variation among the tested peptides. In addition to conventional crustacean AMPs, our work highlights armadillidins as a new and independent family of AMPs specific to the Oniscidea, thus opening new perspectives concerning the study of the immune system of terrestrial isopods.

Ribosomally synthesized peptides, foreground players in microbial interactions: recent developments and unanswered questions

“…This is for instance exemplified by terrestrial isopods that produce an arsenal of HDPs, among which the armadillidins were first isolated from Armadillidium vulgare , which appear to be specific to this class of terrestrial crustaceans. 198 The American cockroach Periplaneta americana produces periplanetasin-4, which would help the insect in its defence against pathogens, especially fungi, by inhibiting communications between mitochondria and vacuoles. 199 In these cases, direct evidence of their effective role in the host defence has not yet been afforded, but other well-documented examples are detailed below.…”

Comparative transcriptome analysis of noble crayfish and marbled crayfish immune response to Aphanomyces astaci challenges

“…ALFs are small proteins with the hydrophobic N-terminal region forming, three β -sheets and three α -helices [35], Pfam: DUF3254. They have been observed in the wide range of crustaceans [106], and they are expressed in a wide range of tissues, showing growth inhibiting activity towards bacterial and fungal microorganisms, as well as opsonic activities [107,108]. Like crustins, they possess a signal peptide domain and can be excreted [101].…”

Structural stability of antimicrobial peptides rich in tryptophan, proline and arginine: a computational study

“…Antimicrobial peptides are often highly conserved in the genome and provoked throughout evolution in all life forms (Becking et al, 2020). They are relatively short, consisting of 10-50 amino acids, display a universal positive charge ranging from þ2 to þ10, and having a substantial proportion (nearly 50%) of hydrophobic residues (Dong et al, 2017;Mahlapuu et al, 2016).…”