The venom composition of the parasitic wasp Chelonus inanitus resolved by combined expressed sequence tags analysis and proteomic approach.
BACKGROUND
Parasitic wasps constitute one of the largest group of venomous animals. Although some physiological effects of their venoms are well documented, relatively little is known at the molecular level on the protein composition of these secretions. To identify the majority of the venom proteins of the endoparasitoid wasp Chelonus inanitus (Hymenoptera: Braconidae), we have randomly sequenced 2111 expressed sequence tags (ESTs) from a cDNA library of venom gland. In parallel, proteins from pure venom were separated by gel electrophoresis and individually submitted to a nano-LC-MS/MS analysis allowing comparison of peptides and ESTs sequences.


RESULTS
About 60% of sequenced ESTs encoded proteins whose presence in venom was attested by mass spectrometry. Most of the remaining ESTs corresponded to gene products likely involved in the transcriptional and translational machinery of venom gland cells. In addition, a small number of transcripts were found to encode proteins that share sequence similarity with well-known venom constituents of social hymenopteran species, such as hyaluronidase-like proteins and an Allergen-5 protein.An overall number of 29 venom proteins could be identified through the combination of ESTs sequencing and proteomic analyses. The most highly redundant set of ESTs encoded a protein that shared sequence similarity with a venom protein of unknown function potentially specific of the Chelonus lineage. Venom components specific to C. inanitus included a C-type lectin domain containing protein, a chemosensory protein-like protein, a protein related to yellow-e3 and ten new proteins which shared no significant sequence similarity with known sequences. In addition, several venom proteins potentially able to interact with chitin were also identified including a chitinase, an imaginal disc growth factor-like protein and two putative mucin-like peritrophins.


CONCLUSIONS
The use of the combined approaches has allowed to discriminate between cellular and truly venom proteins. The venom of C. inanitus appears as a mixture of conserved venom components and of potentially lineage-specific proteins. These new molecular data enrich our knowledge on parasitoid venoms and more generally, might contribute to a better understanding of the evolution and functional diversity of venom proteins within Hymenoptera.
UMR 6035 CNRS, Institut de Recherche sur la Biologie de l'Insecte, Faculté des Sciences et Techniques, Université François-Rabelais, Parc Grandmont, 37200 Tours, France.
Bruno
B
Vincent
Martha
M
Kaeslin
Thomas
T
Roth
Manfred
M
Heller
Julie
J
Poulain
François
F
Cousserans
Johann
J
Schaller
Marylène
M
Poirié
Beatrice
B
Lanzrein
Jean-Michel
JM
Drezen
Sébastien J M
SJ
Moreau
D000595:Amino Acid Sequence; D000818:Animals; D001499:Bayes Theorem; D030541:Databases, Genetic; D004591:Electrophoresis, Polyacrylamide Gel; D020224:Expressed Sequence Tags; D015723:Gene Library; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010271:Parasites / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014862:Wasp Venoms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014863:Wasps / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
D019476:Insect Proteins; D020033:Protein Isoforms; D014862:Wasp Venoms