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Two novel defensin-encoding genes of the Chagas disease vector Triatoma brasiliensis (Reduviidae, Triatominae): gene expression and peptide-structure modeling.

Authors
  • Waniek, Peter J1
  • Castro, Helena C
  • Sathler, Plínio C
  • Miceli, Leonardo
  • Jansen, Ana M
  • Araújo, Catarina A C
  • 1 Laboratório de Biologia de Tripanosomatídeos, Instituto Oswaldo Cruz-IOC/FIOCRUZ, Av. Brasil 4365, Zip Code: 21045-900, Rio de Janeiro, Brazil. [email protected] , (Brazil)
Type
Published Article
Journal
Journal of insect physiology
Publication Date
September 2009
Volume
55
Issue
9
Pages
840–848
Identifiers
DOI: 10.1016/j.jinsphys.2009.05.015
PMID: 19505471
Source
Medline
License
Unknown

Abstract

Defensins are cysteine-rich peptides involved in the innate immunity of insects and many other organisms. In the present study, two novel defensin-encoding cDNAs and the respective genomic DNAs (def3 and def4) of Triatoma brasiliensis were identified and their tissue-specific and temporal expression was characterized. Both of the deduced mature peptides consisted of 43 amino acid residues and were highly similar to previously identified triatomine defensins (81.4-100%). Semi-quantitative RT-PCR data showed that def3 was constitutively expressed in the fat body and was induced in salivary glands and the small intestine at 5 and 3 days after feeding (daf), respectively. The def4 mRNA level was highly up-regulated in the stomach and fat-body tissues at 5 and 3 daf, respectively. The three-dimensional structures of these defensins were predicted using a homology modeling approach with Def-AAA, the defensin from Anopheles gambiae, as template (62-74% identity). A map of the electrostatic potential of these models revealed that, despite their similar folding patterns, mature Def2 and Def4 have a more cationic structure than is the case for Def1 and Def3. Such differences may orient the antimicrobial profile of these defensins against distinct targets in different organs of the insect.

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