昆蟲是世界上種類最多的高等生物類群,，已經(jīng)鑒定的種類達(dá)到100多萬種以上。它們多樣性的分化機(jī)制被認(rèn)為是高度適應(yīng)環(huán)境和長期進(jìn)化的結(jié)果,，但產(chǎn)生的原因和內(nèi)在遺傳機(jī)制并不清楚,。為了研究這種機(jī)制，研究人員嘗試研究多種突變基因及其對(duì)應(yīng)的表型,。
昆蟲的黑化現(xiàn)象被認(rèn)為是理想的模型之一,。在鱗翅目昆蟲的代表種類家蠶長期的飼養(yǎng)和保存過程中，研究人員已收集了多種類型的突變體,。其中,，家蠶黑化突變體，melanism(mln)具有良好的表型特征,。成蟲期,，全體顯著黑化,，在幼蟲期只有頭部、前足和尾斑局部黑化,。
中科院上海生科院植生生態(tài)所黃勇平研究組利用他們已經(jīng)構(gòu)建的家蠶基因定位克隆體系,，完成了家蠶體色突變體mln的定位克隆，并通過表達(dá)譜和表型之間的關(guān)聯(lián)分析,、靶標(biāo)基因的系統(tǒng)進(jìn)化分析,、突變體酶活檢測和靶標(biāo)基因干涉，驗(yàn)證了結(jié)論的可靠性,，并結(jié)合相關(guān)文獻(xiàn)報(bào)道對(duì)昆蟲的體色決定機(jī)制進(jìn)行了討論,。研究結(jié)果發(fā)現(xiàn)家蠶的一種乙酰轉(zhuǎn)移酶基因的突變導(dǎo)致了體色突變體mln的形成——突變體中該基因位點(diǎn)在編碼區(qū)的缺失產(chǎn)生移碼突變，失去活性的突變體乙酰轉(zhuǎn)移酶無法在黑色素代謝途徑中發(fā)揮正常作用,，導(dǎo)致黑色素的過量沉積,。家蠶mln突變體是發(fā)現(xiàn)的第一個(gè)關(guān)于乙酰轉(zhuǎn)移酶參與昆蟲體色決定的表型證據(jù)，而在此之前,，乙酰轉(zhuǎn)移酶是整個(gè)黑色素代謝途徑中唯一一個(gè)還沒有報(bào)道對(duì)應(yīng)表型的酶,。
此項(xiàng)研究成果得到了科技部、國家自然科學(xué)基金的資助,。（生物谷Bioon.com）
生物谷推薦英文摘要：
Development. 2010 Dec;137(23):4083-90.
Disruption of an N-acetyltransferase gene in the silkworm reveals a novel role in pigmentation.
Zhan S, Guo Q, Li M, Li M, Li J, Miao X, Huang Y.
Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
The pigmentation of insects has served as an excellent model for the study of morphological trait evolution and developmental biology. The melanism (mln) mutant of the silkworm Bombyx mori is notable for its strong black coloration, phenotypic differences between larval and adult stages, and its widespread use in strain selection. Here, we report the genetic and molecular bases for the formation of the mln morphological trait. Fine mapping revealed that an arylalkylamine N-acetyltransferase (AANAT) gene co-segregates with the black coloration patterns. Coding sequence variations and expression profiles of AANAT are also associated with the melanic phenotypes. A 126 bp deletion in the mln genome causes two alternatively spliced transcripts with premature terminations. An enzymatic assay demonstrated the absolute loss of AANAT activity in the mutant proteins. We also performed RNA interference of AANAT in wild-type pupae and observed a significant proportion of adults with ectopic black coloration. These findings indicate that functional deletion of this AANAT gene accounts for the mln mutation in silkworm. AANAT is also involved in a parallel melanin synthesis pathway in which ebony plays a role, whereas no pigmentation defect has been reported in the Drosophila model or in other insects to date. To the best of our knowledge, the mln mutation is the first characterized mutant phenotype of insects with AANAT, and this result contributes to our understanding of dopamine metabolism and melanin pattern polymorphisms.
