馴化使家養(yǎng)動(dòng)物的部分性狀與其野生祖先相比發(fā)生了很大改變。一個(gè)典型的例子就是毛色的變化,。野生動(dòng)物的毛色一般會(huì)受到自然選擇的壓力,，而具有隱蔽(保護(hù)色),、交流(如擇偶)或生理調(diào)控等功能。
然而對(duì)于家養(yǎng)動(dòng)物來(lái)說(shuō),，自然選擇壓力放松并被馴化過(guò)程中強(qiáng)烈的人工選擇壓力取代,，使得家養(yǎng)動(dòng)物的毛色更多的用于滿足人們的需要或喜好。這種表型的改變往往會(huì)在馴化目標(biāo)基因上留下人工選擇的分子足跡,，通過(guò)比較該基因在家養(yǎng)動(dòng)物與其野生祖先中的變異與多樣性可以找到這種證據(jù),。盡管先前的研究發(fā)現(xiàn)，調(diào)控哺乳動(dòng)物毛色的一個(gè)關(guān)鍵基因黑色素皮質(zhì)素受體1基因(MC1R)在家豬與野豬中存在不同的進(jìn)化模式,，然而由于缺乏對(duì)馴化過(guò)程中群體事件(如奠基者效應(yīng))的分析和區(qū)分,，未能提供充分的人工選擇證據(jù)。
在中國(guó)科學(xué)院昆明動(dòng)物研究所張亞平院士和施鵬研究員的共同指導(dǎo)下,，云南大學(xué)博士研究生李晶等對(duì)中國(guó)土著家豬與野豬的MC1R基因進(jìn)行了深入研究,，發(fā)現(xiàn)瓶頸效應(yīng)與人工選擇共同導(dǎo)致了中國(guó)家豬MC1R基因的遺傳多樣性降低，而強(qiáng)烈的人工選擇導(dǎo)致一個(gè)與黑色相關(guān)的突變?cè)谥袊?guó)家豬中迅速固定,。
該結(jié)果提示,，黑色家豬可能在早期馴化過(guò)程中受到了特殊偏好，這與中國(guó)古代祭祀中常用純凈黑色家豬作為犧牲的文化一致,，表明MC1R是中國(guó)家豬的一個(gè)人工馴化基因,。此研究不僅為揭示人工選擇改變家養(yǎng)動(dòng)物表型提供了強(qiáng)有力的分子證據(jù)，而且提出了一種區(qū)分瓶頸效應(yīng)與人工選擇作用的簡(jiǎn)單有效的策略,，同時(shí)提供了一個(gè)中國(guó)古代文化偏好對(duì)家養(yǎng)動(dòng)物人工選擇造成影響的有趣范例,。(生物谷Bioon.com)
生物谷推薦原文出處：
Heredity doi: 10.1038/hdy.2009.191
Artificial selection of the melanocortin receptor 1 gene in Chinese domestic pigs during domestication
J Li1,2, H Yang2, J-r Li3, H-p Li3, T Ning1,2, X-R Pan1, P Shi2 and Y-P Zhang1,2
1Laboratory for Conservation and Utilization of Bio-resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, China
2State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
3Department of Computational Genomics, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
Black coat colour is common in Chinese indigenous domestic pigs, but not among their wild ancestors, and it is thus presumed to be a ‘domestication trait.’ To determine whether artificial interference contributes to morphological diversification, we examined nucleotide variation from 157 Chinese domestic pigs and 40 wild boars in the melanocortin receptor 1 (MC1R) gene, which has a key role in the coat pigmentation of Sus scrofa. Compared with a pseudogene GPIP, our results showed that the joint effects of demography and selection have resulted in markedly low genetic diversity of MC1R in Chinese domestic pigs. Coalescent simulation and selection tests further suggest that the fixation of two non-synonymous substitutions associated with black colour is the result of artificial selection. In contrast, a much higher genetic diversity and only a single non-synonymous substitution were found among the wild boars, suggesting a strong functional constraint. Moreover, our conclusion is consistent with the preference for black colour in the ancient Chinese sacrificial culture. This case provides an interesting example of a molecular evaluation of artificial livestock selection and its associated cultural impact in ancient China.
