Tian et al. BMC Genomics 2010, 11:187 http://www.biomedcentral.com/1471-2164/11/187 R E S E A R C H A R T I C L E Open Access Antimicrobial peptide-like genes in Nasonia vitripennis: a genomic perspective Caihuan Tian1, Bin Gao1, Qi Fang2, Gongyin Ye2, Shunyi Zhu1* Abstract Background: Antimicrobial peptides (AMPs) are an essential component of innate immunity which can rapidly respond to diverse microbial pathogens. Insects, as a rich source of AMPs, attract great attention of scientists in both understanding of the basic biology of the immune system and searching molecular templates for anti- infective drug design. Despite a large number of AMPs have been identified from different insect species, little information in terms of these peptides is available from parasitic insects. Results: By using integrated computational approaches to systemically mining the Hymenopteran parasitic wasp Nasonia vitripennis genome, we establish the first AMP repertoire whose members exhibit extensive sequence and structural diversity and can be distinguished into multiple molecular types, including insect and fungal defensin-like peptides (DLPs) with the cysteine-stabilized a-helical and b-sheet (CSab) fold; Pro- or Gly-rich abaecins and hymenoptaecins; horseshoe crab tachystatin-type AMPs with the inhibitor cystine knot (ICK) fold; and a linear a-helical peptide. Inducible expression pattern of seven N. vitripennis AMP genes were verified, and two representative peptides were synthesized and functionally identified to be antibacterial. In comparison with Apis mellifera (Hymenoptera) and several non-Hymenopteran model insects, N. vitripennis has evolved a complex antimicrobial immune system with more genes and larger protein precursors. Three classical strategies that are likely responsible for the complexity increase have been recognized: 1) Gene duplication; 2) Exon duplication; and 3) Exon-shuffling. Conclusion: The present study established the N. vitripennis peptidome associated with antimicrobial immunity by using a combined computational and experimental strategy. As the first AMP repertoire of a parasitic wasp, our results offer a basic platform for further studying the immunological and evolutionary significances of these newly discovered AMP-like genes in this class of insects. Background AMPs constitute essential components of innate immu- nity to rapidly respond to diverse microbial pathogens [1,2]. As key effectors, AMPs directly kill invaders by acting either as pore-formers or metabolic inhibitors [3]. Most AMPs are cationic polypeptides, usually smaller than 100 amino acids in length, with enormous sequence diversity. Based on structural characteristics, these molecules are roughly divided into three different groups [4]: 1) Linear peptides free of cysteines, often forming an a-helical conformation with amphiphilic surface, such as insect cecropins and mellitins, * Correspondence: shunyizhu@hotmail.com 1Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, PR China amphibian magainins and arachnidian meucins [5,6]; 2) Cysteine-rich peptides. The most representative of this group are insect-derived defensins, which belong to the CSab polypeptide superfamily and are conserved across the kingdoms of eukaryotes [7,8], even in bacteria [9,10]; 3) Peptides with unusual bias in certain amino acids, such as glycine-rich tenecin3 [11], proline-rich apidaecin [12], histidine-rich histatin [13] and tryptophan-rich indolicidin [14]. AMPs in this group are unstructured and often enter into bacterial cells to inhibit different metabolic targets [3,15]. Insects, as a rich source of AMPs, attract great atten- tion of scientists in both understanding the basic biology of immune system and searching molecular templates for anti-infective drug design. So far, about 200 such peptides have been identified from insects. In Drosophila © 2010 Tian et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.