棉鈴蟲Helicoverpa armigera是重要的農(nóng)業(yè)害蟲，危害多種作物,。棉鈴蟲具有廣泛的寄主并對常用殺蟲劑產(chǎn)生了抗藥性是其大發(fā)生的兩個(gè)重要因素,。以細(xì)胞色素P450為代表的解毒酶系對植物次生物質(zhì)和殺蟲劑等外源性化合物的代謝解毒作用被認(rèn)為是棉鈴蟲化學(xué)防御的主要武器,，在棉鈴蟲對環(huán)境的適應(yīng)中起著非常重要的作用。由于細(xì)胞色素P450在研究技術(shù)上難度較大,，至今有關(guān)棉鈴蟲細(xì)胞色素P450種類,、結(jié)構(gòu)、功能和調(diào)控的知識還非常缺乏,。
中國科學(xué)院動(dòng)物研究所農(nóng)業(yè)蟲害鼠害綜合治理研究國家重點(diǎn)實(shí)驗(yàn)室邱星輝研究組,，通過對棉鈴蟲細(xì)胞色素P450新基因的克隆鑒定，揭示了棉鈴蟲細(xì)胞色素P450的分子多樣性,。通過對兩個(gè)近緣關(guān)系很近的同源基因CYP9A12與CYP9A17的比較研究發(fā)現(xiàn),，雖然兩者的基因序列和基因組結(jié)構(gòu)高度相似，但在轉(zhuǎn)錄調(diào)控方面（基礎(chǔ)表達(dá)和誘導(dǎo)表達(dá)）存在明顯差異,。利用基于最大似然法的統(tǒng)計(jì)學(xué)模型從CYP9A亞家族的13個(gè)細(xì)胞色素 P450基因中檢測出了6個(gè)正選擇位點(diǎn),，根據(jù)已解析的細(xì)胞色素P450蛋白結(jié)構(gòu)預(yù)測了棉鈴蟲CYP9A17蛋白結(jié)構(gòu)，結(jié)果顯示這6個(gè)氨基酸位點(diǎn)均位于P450的底物結(jié)合區(qū)域（SRS）或底物進(jìn)入催化位點(diǎn)的通道,，表明它們的加速進(jìn)化可能對P450底物的特異性與代謝活性產(chǎn)生重要影響。通過研究四種不同外源性化合物對9種CYP6和 CYP9家族的細(xì)胞色素P450基因的轉(zhuǎn)錄調(diào)控效應(yīng)發(fā)現(xiàn),，棉鈴蟲細(xì)胞色素P450基因具有復(fù)雜的表達(dá)調(diào)控網(wǎng)絡(luò),，不同細(xì)胞色素P450基因的轉(zhuǎn)錄表達(dá)因化合物的種類與濃度不同而有差異，并表現(xiàn)出一定程度的組織特異性,。
細(xì)胞色素P450是基因超家族,，多種細(xì)胞色素P450共存于同一生物體被認(rèn)為是基因重復(fù)和隨后長期進(jìn)化的結(jié)果?；蛑貜?fù)是非常普遍的生物現(xiàn)象,，為新基因的產(chǎn)生提供了原材料，在生物進(jìn)化過程中發(fā)揮著非常重要的作用,。通過上述研究,，我們提出了棉鈴蟲細(xì)胞色素P450基因轉(zhuǎn)錄調(diào)控水平的亞功能化以及蛋白質(zhì)水平的適應(yīng)性進(jìn)化的證據(jù)，推測這些進(jìn)化機(jī)制可能導(dǎo)致棉鈴蟲細(xì)胞色素P450種類,、生化和生物學(xué)功能以及基因表達(dá)調(diào)控模式的多樣化,。研究結(jié)果可以部分解釋棉鈴蟲能耐受不同寄主植物中的有毒次生性物質(zhì)、對化學(xué)殺蟲劑容易產(chǎn)生抗藥性，因而長期以來成為農(nóng)作物主要害蟲的原因,。
以上研究得到了國家973項(xiàng)目（2006CB102003）和國家自然科學(xué)基金（No. 30370946）的資助,。研究結(jié)果發(fā)表在昆蟲毒理學(xué)的主流刊物Pest Management Science 和Pesticide Biochemistry and Physiology上。 論文第一作者為博士研究生周小潔,，責(zé)任作者為邱星輝博士,。（生物谷Bioon.com）
生物谷推薦原文出處：
Pest Management Science DOI: 10.1002/ps.1832
CYP9A12 and CYP9A17 in the cotton bollworm, Helicoverpa armigera: sequence similarity, expression profile and xenobiotic response
Xiaojie Zhou1,2, Caixia Ma3, Mei Li1, Chengfa Sheng1, Huixia Liu3, Xinghui Qiu1,*
Keywords:Helicoverpa armigera;cytochrome P450;CYP9A17;CYP9A12;expression pattern;xenobiotic response
Abstract
BACKGROUND:Helicoverpa armigera (Hübner) causes severe losses in many crops including cotton. Cytochrome P450s play crucial roles in the metabolism of many important compounds in various organisms. The authors attempt to identify new cytochrome P450 genes and investigate their expression profile and xenobiotic response in order to understand the nature and roles of cytochrome P450s in this important pest.
RESULTS: A novel P450 cDNA (CYP9A17), encoding a protein of 531 amino acid residues, was isolated from H. armigera. CYP9A17 is a typical microsomal P450, showing the highest (93.9%) amino acid identity with CYP9A12 from H. armigera. The high similarity is not only found between cDNAs, but also between the intron–exon organisation. CYP9A12 is constitutively universally expressed in all four life stages and in all tested larval tissues, whereas CYP9A17 is specifically expressed in the larval midgut and fat body. Real-time quantitative RT-PCR showed that the level of both CYP9A12 and CYP9A17 mRNA is affected in dose-dependent and tissue-specific manners by deltamethrin, gossypol and phenobarbital.
CONCLUSION:CYP9A12 and CYP9A17 showed high sequence identity, but with differential expression patterns, suggesting that CYP9A12 and CYP9A17 genes in H. armigera might diverge via subfunctionalisation after the gene duplication event. Copyright ? 2009 Society of Chemical Industry
