Big Defensins, a Diverse Family of Antimicrobial Peptides That Follows Different Patterns of Expression in Hemocytes of the Oyster Crassostrea gigas

Type Article
Date 2011-09
Language English
Author(s) Rosa Rafael D., Santini Adrien, Fievet Julie, Bulet Philippe, Destoumieux Garzon Delphine, Bachere Evelyne
Affiliation(s) IFREMER, Univ Montpellier 2,CNRS, IRD, Montpellier, France
CNRS, Université Montpellier 2, IRD, and Université Montpellier 1, UMR 5119 ‘‘Ecologie des Systèmes Marins Côtiers’’, Montpellier, France
UJF Grenoble, AGIM, FRE 3405, CNRS EPHE 1, La Tronche, France
AGIM, Plateforme BioPark Archamps, Archamps, France
Source Plos One (1932-6203) (Public Library Science), 2011-09 , Vol. 6 , N. 9 , P. 1-11
DOI 10.1371/journal.pone.0025594
WOS© Times Cited 75
Abstract Background: Big defensin is an antimicrobial peptide composed of a highly hydrophobic N-terminal region and a cationic C-terminal region containing six cysteine residues involved in three internal disulfide bridges. While big defensin sequences have been reported in various mollusk species, few studies have been devoted to their sequence diversity, gene organization and their expression in response to microbial infections. Findings: Using the high-throughput Digital Gene Expression approach, we have identified in Crassostrea gigas oysters several sequences coding for big defensins induced in response to a Vibrio infection. We showed that the oyster big defensin family is composed of three members (named Cg-BigDef1, Cg-BigDef2 and Cg-BigDef3) that are encoded by distinct genomic sequences. All Cg-BigDefs contain a hydrophobic N-terminal domain and a cationic C-terminal domain that resembles vertebrate beta-defensins. Both domains are encoded by separate exons. We found that big defensins form a group predominantly present in mollusks and closer to vertebrate defensins than to invertebrate and fungi CS alpha beta-containing defensins. Moreover, we showed that Cg-BigDefs are expressed in oyster hemocytes only and follow different patterns of gene expression. While Cg-BigDef3 is non-regulated, both Cg-BigDef1 and Cg-BigDef2 transcripts are strongly induced in response to bacterial challenge. Induction was dependent on pathogen associated molecular patterns but not damage-dependent. The inducibility of Cg-BigDef1 was confirmed by HPLC and mass spectrometry, since ions with a molecular mass compatible with mature Cg-BigDef1 (10.7 kDa) were present in immune-challenged oysters only. From our biochemical data, native Cg-BigDef1 would result from the elimination of a prepropeptide sequence and the cyclization of the resulting N-terminal glutamine residue into a pyroglutamic acid. Conclusions: We provide here the first report showing that big defensins form a family of antimicrobial peptides diverse not only in terms of sequences but also in terms of genomic organization and regulation of gene expression.
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Rosa Rafael D., Santini Adrien, Fievet Julie, Bulet Philippe, Destoumieux Garzon Delphine, Bachere Evelyne (2011). Big Defensins, a Diverse Family of Antimicrobial Peptides That Follows Different Patterns of Expression in Hemocytes of the Oyster Crassostrea gigas. Plos One, 6(9), 1-11. Publisher's official version : https://doi.org/10.1371/journal.pone.0025594 , Open Access version : https://archimer.ifremer.fr/doc/00050/16096/