院士继Science后再发遗传机制新成果

　　

生物通报道，中国科学院昆明动物研究所张亚平院士近期发表文章，通过遗传技术确认狗起源中国，这一成果受学术界肯定，被《Science》以专题形式报道。近日，他所带领的研究小组再度在《Molecular Biology and Evolution》发表文章，揭示灵长目疣猴亚科食性适应性进化遗传机制的新认识。

 

胰核糖核酸酶（RNASE1）是非常重要的消化酶，是研究基因进化以及新功能产生的一个重要基因家族。早期进化分析表明RNASE1基因重复与灵长目疣猴亚科物种适应以树叶为食的功能适应紧密相关。

 

然而，关于RNASE1基因重复在疣猴亚科亚洲叶猴和非洲叶猴中的进化模式目前存在着两种截然不同的假说：一是Zhang等人在2006年基于基因全长分析提出的独立重复假说（independent duplication hypothesis），即RNASE1基因重复发生在亚洲叶猴和非洲叶猴分歧之后，在亚洲叶猴和非洲叶猴中独立产生；二是Schienman等（2006）和Xu 等(2009)基于编码区分析提出的一次重复假说（one duplication event hypothesis），即基因重复发生在亚洲叶猴和非洲叶猴分歧之前，并认为基于非编码区和基因全长分析得到的独立重复假说是由于基因间频繁的基因转换造成的。

 

与以往只基于少量疣猴亚科代表物种的研究相比，云南大学于黎研究员，王小燕硕士研究生和中国科学院昆明动物研究所张亚平院士对疣猴亚科7个属共10个代表物种的RNASE1基因进行系统和深入的研究，结果发现基于编码区，非编码区和基因全长构建的系统发育树都支持RNASE1基因重复发生在亚洲叶猴和非洲叶猴物种形成之后，即独立重复假说。而且，没有发现明显的基因转换证据，并不支持一次重复假说中提出的基因转换在疣猴亚科RNASE1进化中起重要作用的观点。

 

此外，选择压力分析也在重复基因拷贝的祖先枝上检测到了正选择作用。而且，也检测到了以前研究中没有发现的正选择位点和平行替换位点，这为后续的功能实验奠定了基础。该研究结果不仅提供了更为清晰的疣猴亚科RNASE1基因进化模式，而且更全面了解了疣猴亚科物种独特的以树叶为食的适应性进化遗传基础。

 

该研究工作得到了国际同行的高度评价，他们认为“这项研究不只对疣猴亚科物种的研究非常重要，而且对于其它灵长类，以及更广的科学领域也尤为重要”。

 

生物通推荐原文检索

Research Article

Adaptive evolution of digestive RNASE1 genes in leaf-eating monkeys revisited: new insights from 10 additional Colobines

Li Yu*,$, Xiao-yan Wang*,$, Wei Jin*, Peng-tao Luan*, Nelson Ting and Ya-ping Zhang*,

* Laboratory for Conservation and Utilization of Bio-resource & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, 650091, PR, China

 State Key Laboratory of Genetic Resources and Evolution, and Laboratory of Molecular Biology of Domestic Animals, Kunming Institute of Zoology, Kunming 650223, China

 Anthropology Program, City University of New York Graduate Center, 365 Fifth Avenue, New York, NY 10016, USA

 

Correspondence to: Ya-ping Zhang, State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Kunming 650223, China, Phone: [phone], FAX: [phone], E-mail: [e-mail] or [e-mail]

 

Li Yu, Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming 650091, China; Phone: [phone], FAX: [phone], E-mail: [e-mail]

 

Received for publication June 22, 2009. Revision received September 1, 2009. Accepted for publication September 4, 2009.

 

Pancreatic RNase genes implicated in the adaptation of the colobine monkeys to leaf-eating have long intrigued evolutionary biologists since the identification of a duplicated RNASE1 gene with enhanced digestive efficiencies in Pygathrix nemaeus. The recent emergence of two contrasting hypotheses, i.e., independent duplication and one duplication event hypotheses, make it into focus again. Current understanding of Colobine RNASE1 gene evolution largely depends on the analyses of few colobine species. The present study with more intensive taxonomic and character sampling not only provides a clearer picture of Colobine RNASE1 gene evolution, but also allows to have a more thorough understanding about the molecular basis underlying the adaptation of Colobinae to the unique leaf-feeding lifestyle. The present broader and detailed phylogenetic analyses yielded two important findings: (1) All trees based on the analyses of coding, noncoding and both regions provided consistent evidence indicating RNASE1 duplication occurred after Asian and African colobines speciation, i.e., independent duplication hypothesis; (2) No obvious evidence of gene conversion in RNASE1 gene was found, favoring independent evolution of Colobine RNASE1 gene duplicates. The conclusion drawn from previous studies that gene conversion has played a significant role in the evolution of Colobine RNASE1 was not supported. Our selective constraint analyses also provided interesting insights, with significant evidence of positive selection detected on ancestor lineages leading to duplicated gene copies. The identification of a handful of new adaptive sites and amino acid changes that have not been characterized previously also provide a necessary foundation for further experimental investigations of RNASE1 functional evolution in Colobinae.