金小蜂是一類寄生性昆蟲,，靶向許多人類疾病傳播的載體（如家蠅等）,，在害蟲生物防治上具有重要地位。作為一個(gè)新的模式昆蟲,，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)首次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,，組建了第一個(gè)寄生性昆蟲抗微生物肽基因藍(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免疫防御分子復(fù)雜度增加的最主要原因,。
該系列研究工作的科學(xué)意義在于：1）在國(guó)際上首次建立了第一個(gè)寄生性昆蟲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,。
研究主要結(jié)果發(fā)表在國(guó)際刊物《過(guò)程生化》，《發(fā)育與比較免疫學(xué)》和《BMC基因組學(xué)》上,。(生物谷Bioon.com)
生物谷推薦原文出處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 accurately 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.
