生物谷:细菌等微生物之间的横向基因转移(lateral gene transfer)现象频繁发生,这对于它们的进化发展至关重要。美国科学家最新研究发现,细菌也能将基因转移到复杂有机体中去。这将促使科学家重新思考种间基因转移在进化中的作用,也使得遗传学家今后在为新基因组排序时,不得不采用新的方法以过滤掉细菌基因的污染。相关论文8月30日在线发表于《科学》上。
一直以来,科学家认为细菌和多细胞有机体之间的基因转移是很少见的。已知仅有的几个例子包括某种寄生细菌(Wolbachia)的基因能够转移到昆虫及其它无脊椎动物体内。
在最新实验中,美国奎格文特研究所(J. Craig Venter Institute)的Julie Dunning Hotopp和同事对从昆虫基因组中发现的Wolbachia基因序列展开了研究。他们根据动物遗传数据库筛选Wolbachia的基因序列,结果在三种黄蜂和四种蠕虫基因组中发现了Wolbachia的基因序列。在黄蜂中,这些基因序列有96%与黄蜂生存地的Wolbachia DNA相匹配。
在另外的实验中,研究人员用抗生素处理一种热带果蝇(Drosophila ananassae)的卵巢,在确保Wolbachia基因序列来自该种果蝇基因组后,将这种果蝇基因重新排序,结果惊讶地发现这种果蝇的一个染色体上含有几乎整个Wolbachia基因组,超过一百万个DNA碱基对。这些DNA中绝大多数已经丧失功能,不过研究人员从30个Wolbachia基因中发现了RNA副本,这表明这些基因曾被转录过,已经迈出了蛋白质制造的第一步。
日本东京大学的进化生物学家Takema Fukatsu认为,横向转移可能比我们先前预想的要广泛得多。他表示,此次研究结果激动人心,但是问题是Wolbachia基因是否具有活性,因为它们并没有表现出任何的生物学功能。如果将来有实验确认了这些基因能够进行表达,那么这将是对进化过程的一个空前的认识!(科学网 梅进/编译)
原始出处:
Published Online August 30, 2007
Science DOI: 10.1126/science.1142490
Submitted on March 13, 2007
Accepted on July 2, 2007
Widespread Lateral Gene Transfer from Intracellular Bacteria to Multicellular Eukaryotes
Julie C. Dunning Hotopp 1*, Michael E. Clark 2, Deodoro C. S. G. Oliveira 2, Jeremy M. Foster 3, Peter Fischer 4, Mónica C. Muñoz Torres 5, Jonathan D. Giebel 2, Nikhil Kumar 1, Nadeeza Ishmael 1, Shiliang Wang 1, Jessica Ingram 3, Rahul V. Nene 1, Jessica Shepard 1, Jeffrey Tomkins 5, Stephen Richards 6, David J. Spiro 1, Elodie Ghedin 7, Barton E. Slatko 3, Hervé Tettelin 1, John H. Werren 2
1 The Institute for Genomic Research, J. Craig Venter Institute, 9712 Medical Center Drive, Rockville, MD 20850, USA.
2 Department of Biology, University of Rochester, Rochester, NY 14627, USA.
3 Molecular Parasitology Division, New England Biolabs Inc., 240 County Road, Ipswich, MA 01938, USA.
4 Department of Internal Medicine, Infectious Diseases Division, Washington University School of Medicine, St. Louis, MO 63110, USA.
5 Clemson University Genomics Institute, 304 BRC, 51 New Cherry St, Clemson, SC 29634, USA.
6 Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA.
7 The Institute for Genomic Research, J. Craig Venter Institute, 9712 Medical Center Drive, Rockville, MD 20850, USA.; Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
* To whom correspondence should be addressed.
Julie C. Dunning Hotopp , E-mail: jdunning@jcvi.org
These authors contributed equally to this work.
Present address: Brown University, Providence, RI 02912, USA.
Present address: Pace University, New York, NY 10038, USA.
These authors contributed equally to this work.
Although common among bacteria, lateral gene transfer—the movement of genes between distantly related organisms—is thought to occur only rarely between bacteria and multicellular eukaryotes. However, the presence of endosymbionts, such as Wolbachia pipientis, within some eukaryotic germlines may facilitate bacterial gene transfers to eukaryotic host genomes. We therefore examined host genomes for evidence of gene transfer events from Wolbachia bacteria to their hosts. We found and confirmed transfers into the genomes of 4 insect and 4 nematode species that range from nearly the entire Wolbachia genome (>1 megabase) to short (<500 base pairs) insertions. Potential Wolbachia to host transfers were also detected computationally in three additional sequenced insect genomes. We also show that some of these inserted Wolbachia genes are transcribed within eukaryotic cells lacking endosymbionts. Therefore, heritable lateral gene transfer occurs into eukaryotic hosts from their prokaryote symbionts, potentially providing a mechanism for acquisition of new genes and functions.