金小蜂是一類寄生性昆蟲(chóng)，靶向許多人類疾病傳播的載體（如家蠅等），在害蟲(chóng)生物防治上具有重要地位。作為一個(gè)新的模式昆蟲(chóng)，近期公布的麗蠅蛹集金小蜂（Nasonia vitripennis）全基因組序列為研究寄生性昆蟲(chóng)天然免疫的分子和進(jìn)化機(jī)制奠定了基礎(chǔ)。

運(yùn)用進(jìn)化基因組學(xué)的方法，中科院動(dòng)物研究所朱順義研究員領(lǐng)導(dǎo)的團(tuán)隊(duì)從麗蠅蛹集金小蜂基因組中鑒定了44個(gè)抗微生物肽新基因，組建了*個(gè)寄生性昆蟲(chóng)抗微生物肽基因藍(lán)圖。進(jìn)一步研究證實(shí)，金小蜂抗微生物肽基因在細(xì)菌攻擊后轉(zhuǎn)錄本的表達(dá)水平顯著上調(diào)。利用化學(xué)合成和遺傳重組表達(dá)的蛋白，他們對(duì)其中不同類別的代表性序列進(jìn)行了結(jié)構(gòu)、功能和進(jìn)化研究，確定了4個(gè)抗微生物肽基因的抗微生物活性，發(fā)現(xiàn)γ－core區(qū)域是防御肽Navidefensin2-2的抗菌活性表面。他們的結(jié)果還表明，基因重復(fù)和功能區(qū)域的正選擇可能驅(qū)動(dòng)了金小蜂防御肽基因家族的適應(yīng)性進(jìn)化。

此外，運(yùn)用比較基因組學(xué)的方法，研究人員還發(fā)現(xiàn)，與同為膜翅目的意大利蜜蜂（Apis mellifera）相比，金小蜂直系同源的抗微生物肽基因發(fā)生了明顯的變化。主要表現(xiàn)在基因數(shù)量擴(kuò)張，蛋白質(zhì)末端延長(zhǎng)，功能域的串聯(lián)重復(fù)和融合以及結(jié)構(gòu)多樣性改變等。他們發(fā)現(xiàn)，基因和外顯子重復(fù)以及外顯子改組是造成這類寄生性昆蟲(chóng)免疫防御分子復(fù)雜度增加的zui主要原因。

該系列研究工作的科學(xué)意義在于：1）在上建立了*個(gè)寄生性昆蟲(chóng)的全套抗微生物肽數(shù)據(jù)，為金小蜂天然免疫以及寄生和免疫的關(guān)系研究奠定了基礎(chǔ)；2）該研究發(fā)展的快速鑒定抗微生物肽基因的計(jì)算基因組學(xué)策略，有望拓展到其它模式生物，包括人類抗微生物肽新基因的發(fā)現(xiàn)，這將加速人類對(duì)于抗微生物肽介導(dǎo)的天然免疫防御網(wǎng)絡(luò)進(jìn)化的研究。

推薦原文出處1：

Process Biochemistry doi:10.1016/j.procbio.2009.08.017

Characterization of a hymenoptaecin-like antimicrobial peptide in the parasitic wasp Nasonia vitripennis
Bin Gaoa and Shunyi Zhu, a,

a Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China

Hymenoptaecin is a Hymenoptera insect-specific, glycine-rich antimicrobial peptide （AMP） found in non-parasitic bees. Here, we describe a unique hymenoptaecin-like gene （named nahymenoptaecin-1） in the parasitic wasp Nasonia vitripennis, which codes for a larger protein precursor with a carboxyl-terminal hymenoptaecin-like domain （HLD） similar to the bee hymenoptaecin. We recombinantly produced its full-length bioactive form as well as 1–33 and 34–98 fragments （named HLD-n and HLD-c, respectively）. Recombinant HLD exhibited activity against Gram-negative and Gram-positive bacteria at micromolar concentrations. Compared to the full-length peptide, HLD-c possessed similar potency in inhibiting the growth of Stenotrophomonus but had a narrower antibacterial spectrum, whereas HLD-n only displayed weak effect on Stenotrophomonus, suggesting that HLD-n is a crucial determinant for bacterial target selectivity while HLD-c represents its active unit for the whole molecule. Circular dichroism analysis combined with ab initio structure prediction by Robetta indicated that HLD-n adopts a random coil conformation whereas glycine-rich HLD-c forms a loose β-sheet structure. Relative to bee hymenoptaecin, the upstream region of HLD contains two accuray repeated proline-rich AMP-like peptides instead of an acidic propeptide. Such difference could be a consequence of exon shuffling of autonomous modules after speciation.

推薦原文出處2：

Dev Comp Immunol. PMID: 20097222

Identification and characterization of the parasitic wasp Nasonia defensins: positive selection targeting the functional region
Gao B, Zhu S.

Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.

Defensin is a crucial component of innate immunity highly conserved across different insect orders. Here, we report identification and characterization of defensins in the parasitic wasp Nasonia （Hymenoptera: Pteromalidae）. In comparison with those in the non-parasitic insect Apis mellifera, two different subtypes of defensins （defensin1 and defensin2） have undergone independent gene duplication to create a mutigene family of five members （named 1-1, 1-2, 2-1, 2-2 and 2-3） in the Nasonia lineage. Such duplication occurred before the divergence of three sibling species （N. vitripennis, N. giraulti and N. longicornis） and the duplicated genes was subsequently subjected to positive selection at the amino-terminal loop and the gamma-core region. RT-PCR identified that only the subtype 1 of defensins were constitutively expressed in the N. vitripennis adult stage and none of the five defensins was expressed in other developmental stages （i.e. the infected Musca domestica pupae）. A functional form of 2-2 in N. vitripennis （named navidefensin2-2） was produced in Escherichia coli by an on-column refolding approach. The recombinant peptide presented a typical defensin structure, as identified by CD analysis, and selectively inhibited the growth of two Gram（+） bacteria at low micromolar concentrations. The bioactive surface responsible for antibacterial activity of navidefensin2-2 was identified in the gamma-core region of this molecule. Positive selection targeting the antibacterial region of defensins could be a consequence of evolutionary arms race between Nasonia and its pathogens. Copyright 2010 Elsevier Ltd. All rights reserved.

上海勁馬生物（）推薦原文出處3：

BMC Genomics 2010, 11:187doi:10.1186/1471-2164-11-187

Antimicrobial peptide-like genes in Nasonia vitripennis: a genomic perspective
Caihuan Tian1 , Bin Gao1 , Qi Fang2 , Gongyin Ye2  and Shunyi Zhu1

1 Group 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
2 State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310029, PR China

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 α-helical and β-sheet （CSαβ） fold; Pro- or Gly-rich abaecins and hymenoptaecins; horseshoe crab tachystatin-type AMPs with the inhibitor cystine knot （ICK） fold; and a linear α-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.