title: X-tox: an atypical defensin derived family of immune-related proteins specific to Lepidoptera.
abstract: We report here the isolation in Spodoptera frugiperda (Lepidoptera) of an immune-related protein (hereafter named Spod-11-tox), characterized by imperfectly conserved tandem repeats of 11 cysteine-stabilized alpha beta motifs (CS-alphabeta), the structural scaffold characteristic of invertebrate defensins and scorpion toxins. Spod-11-tox orthologs were only found in Lepidopteran species, suggesting that this new protein family (named X-tox) is specific to this insect order. Moreover, phylogenetic analysis suggests that X-tox proteins represent a new class of proteins restricted to Lepidoptera and likely derived from Lepidopteran defensins. In S. frugiperda, analysis of gene expression revealed that spod-11-tox is rapidly induced by infection. However, and conversely to what is known for most insect antimicrobial peptides (AMP), spod-11-tox is mainly expressed in blood cells. Moreover, recombinant Spod-11-tox produced in the Sf9 cell line does not show any antimicrobial activity. Altogether, these results suggest that although X-tox proteins are derived from defensins, they may play a different and still unknown role in Lepidoptera immune response.
authors.affiliation: Ecologie Microbienne des Insectes et Interactions Hôte-Pathogène, Université de Montpellier II, 34095 Montpellier, France.
authors.forename: Pierre-Alain
authors.initials: PA
authors.lastname: Girard
authors.forename: Yvan
authors.initials: Y
authors.lastname: Boublik
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Wheat
authors.forename: Anne-Nathalie
authors.initials: AN
authors.lastname: Volkoff
authors.forename: F
authors.initials: F
authors.lastname: Cousserans
authors.forename: Michel
authors.initials: M
authors.lastname: Brehélin
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Escoubas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D023082:Defensins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000494:pharmacology; D019476:Insect Proteins / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000494:pharmacology; D018411:Spodoptera / Q000276:immunology*; D020080:Tandem Repeat Sequences
chemical_list: D023082:Defensins; D019476:Insect Proteins; D011994:Recombinant Proteins