生物谷报道：近日，昆明动物所马普青年科学家小组的博士生杨爽等在导师王文研究员的指导下，与芝加哥大学的科学家合作，经过筛选和分析大量的果蝇年轻基因，发现非等位的同源重组(non-allelic homologous recombination)远比传统认为的非同源重组重要得多，从而取得了对基因重复机制的全新认识。
本结果的论文于1月18日正式发表于国际著名遗传学刊物PLoS Genetics上。此前，该小组已在新基因起源方面取得了一些研究成果，在Nature Genetics、Plant Cell等学术刊物发表了一系列文章，引起了国际同行的关注。
生物谷推荐英文原文：
PLoS Genetics
Received: August 22, 2007; Accepted: November 27, 2007; Published: January 18, 2008
Repetitive Element-Mediated Recombination as a Mechanism for New Gene Origination in Drosophila
Shuang Yang1,2, J. Roman Arguello3, Xin Li1,2, Yun Ding1,2, Qi Zhou1,2, Ying Chen4, Yue Zhang1, Ruoping Zhao1, Frédéric Brunet3¤, Lixin Peng1, Manyuan Long3,4*, Wen Wang1*
1 Chinese Academy of Sciences (CAS)—Max Planck Junior Research Group, Key Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China, 2 Graduate School of Chinese Academy Sciences, Beijing, China, 3 Committee on Evolutionary Biology, The University of Chicago, Chicago, Illinois, United States of America, 4 Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois, United States of America
Previous studies of repetitive elements (REs) have implicated a mechanistic role in generating new chimerical genes. Such examples are consistent with the classic model for exon shuffling, which relies on non-homologous recombination. However, recent data for chromosomal aberrations in model organisms suggest that ectopic homology-dependent recombination may also be important. Lack of a dataset comprising experimentally verified young duplicates has hampered an effective examination of these models as well as an investigation of sequence features that mediate the rearrangements. Here we use 7,000 cDNA probes (112,000 primary images) to screen eight species within the Drosophila melanogaster subgroup and identify 17 duplicates that were generated through ectopic recombination within the last 12 mys. Most of these are functional and have evolved divergent expression patterns and novel chimeric structures. Examination of their flanking sequences revealed an excess of repetitive sequences, with the majority belonging to the transposable element DNAREP1 family, associated with the new genes. Our dataset strongly suggests an important role for REs in the generation of chimeric genes within these species.
Figure 1.An Example Illustrating the Detection of New Genes
(A) The probe LD47348 (CG10595) detected two signals in the clade of D. yakuba-santomea-teissieri while only detecting one signal in other species. The new additional signal suggests a new gene candidate.
(B) Southern hybridization results further confirm the extra copy in the D. yakuba-santomea-teissieri clade (M is 1-kb extension marker [Invitrogen]). Lanes 1–8 correspond to Xho I digested DNAs of D. yakuba, D. teissieri, D. santomea, D. erecta, D. melanogaster, D. simulans, D. mauritiana, and D. sechellia, respectively).
(C) Cartoon figure displaying the gene structures of the parental gene (d, or CG10595) and the new duplicate (d-r). The duplicated region is indicated by vertical dash lines. d-r recruited one upstream exon as indicated by yellow box.
(D) Expression patterns of the parental gene. (E) expression patterns of the new gene d-r revealed by one round of RT-PCR and a second round of nested PCR (M indicates DL2000 DNA molecular marker (Takara); E+, E−, L2+, L2−, L3+, L3−, P+, P−, A+, and A− correspond to positive and negative reactions for embryos, second instar larvae, third instar larvae, pupae, and adults, respectively). From these gels, it is clear that d-r is only expressed in the third instar larvae while the parental copy is expressed ubiquitously. All the bands in the negative control lanes are primer dimer bands. E+ and L3+ are weak but clearly visible.
