据4月10日的《科学》杂志报道，科学家们在一项研究中说，一组古老的绿藻具有令人诧异的基因多元性，而这可能为人们提供绿色植物是如何进化的线索。
Alexandra Worden及其同僚对两株Micromonas海藻的基因组进行了测序。该海藻株是陆地植物的远古亲缘植物，它们存在于全世界各地的海洋中。 文章的作者说，这些基因组揭露了这些远祖海藻所启动的数十亿年的植物进化和地球被绿化的轨迹特征。 该国际研究团队发现，在这两株海藻中存在着始料未及的遗传变异水平，它们所遵循的是不同的进化途径。
研究人员还发现了重要细胞器及细胞过程的标志，如基因沉默及硫胺的生物合成。 其中一株看来是独特转位因子的一个重要来源，这种转位因子过去在对Sargasso Sea的一个“宏基因组”的研究中曾被发现。 正如John Archibald在一篇相关的Perspective中所写的，这些结果可帮助解释为什么该基因“工具包”可能已经存在于当今陆地植物和绿藻的祖先植物之中。（生物谷Bioon.com）
生物谷推荐原始出处：
Science 10 April 2009: DOI: 10.1126/science.1167222
Green Evolution and Dynamic Adaptations Revealed by Genomes of the Marine Picoeukaryotes Micromonas
Alexandra Z. Worden,1* Jae-Hyeok Lee,2 Thomas Mock,3 Pierre Rouzé,4 Melinda P. Simmons,1 Andrea L. Aerts,5 Andrew E. Allen,6 Marie L. Cuvelier,1,7 Evelyne Derelle,8 Meredith V. Everett,7 Elodie Foulon,9 Jane Grimwood,5,10 Heidrun Gundlach,11 Bernard Henrissat,12 Carolyn Napoli,13 Sarah M. McDonald,1 Micaela S. Parker,3 Stephane Rombauts,4 Aasf Salamov,5 Peter Von Dassow,9 Jonathan H. Badger,6 Pedro M. Coutinho,11 Elif Demir,1 Inna Dubchak,5 Chelle Gentemann,14 Wenche Eikrem,15 Jill E. Gready,16 Uwe John,17 William Lanier,18 Erika A. Lindquist,5 Susan Lucas,5 Klaus F. X. Mayer,10 Herve Moreau,8 Fabrice Not,9 Robert Otillar,5 Olivier Panaud,19 Jasmyn Pangilinan,5 Ian Paulsen,20 Benoit Piegu,19 Aaron Poliakov,5 Steven Robbens,4 Jeremy Schmutz,5,10 Eve Toulza,21 Tania Wyss,22 Alexander Zelensky,23 Kemin Zhou,5 E. Virginia Armbrust,3 Debashish Bhattacharya,18 Ursula W. Goodenough,2 Yves Van de Peer,4 Igor V. Grigoriev5
Picoeukaryotes are a taxonomically diverse group of organisms less than 2 micrometers in diameter. Photosynthetic marine picoeukaryotes in the genus Micromonas thrive in ecosystems ranging from tropical to polar and could serve as sentinel organisms for biogeochemical fluxes of modern oceans during climate change. These broadly distributed primary producers belong to an anciently diverged sister clade to land plants. Although Micromonas isolates have high 18S ribosomal RNA gene identity, we found that genomes from two isolates shared only 90% of their predicted genes. Their independent evolutionary paths were emphasized by distinct riboswitch arrangements as well as the discovery of intronic repeat elements in one isolate, and in metagenomic data, but not in other genomes. Divergence appears to have been facilitated by selection and acquisition processes that actively shape the repertoire of genes that are mutually exclusive between the two isolates differently than the core genes. Analyses of the Micromonas genomes offer valuable insights into ecological differentiation and the dynamic nature of early plant evolution.
1 Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039 USA.
2 Department of Biology, Washington University at St. Louis, St. Louis, MO 63130, USA.
3 School of Oceanography, University of Washington, Seattle, WA 98195, USA.
4 Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB) and Department of Molecular Genetics, Ghent University, 9052 Gent, Belgium.
5 U.S. Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, CA 94598, USA.
6 J. Craig Venter Institute, San Diego, CA 92121, USA.
7 Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA.
8 Observatoire Océanologique, CNRS–Université Pierre et Marie Curie, 66651 Banyuls sur Mer, France.
9 Station Biologique de Roscoff, CNRS–Université Pierre et Marie Curie, Roscoff Cedex, France.
10 Stanford Human Genome Center, Stanford University School of Medicine, Palo Alto, CA 94304, USA.
11 Institute of Bioinformatics and System Biology, German Research Center for Environmental Health, 85764 Neuherberg, Germany.
12 Architecture et Fonction des Macromolécules Biologiques, Universities of Aix-Marseille I and II, Marseille 13288, France.
13 Biology Institute, University of Arizona, Tucson, AZ 85719, USA.
14 Remote Sensing Systems, Santa Rosa, CA 95401, USA.
15 Avdeling for Marinbiologi og Limnologi, University of Oslo, Oslo N-0316, Norway.
16 Division of Molecular Bioscience, College of Medicine, Biology and the Environment, Australian National University, Canberra ACT 2601, Australia.
17 Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen, Bremerhaven 27570, Germany.
18 Department of Biology, University of Iowa, Iowa City, IA 52242, USA.
19 Laboratoire Genome et Development des Plantes Université de Perpignan, 66860 Perpignan, France.
20 Department of Chemistry and Biomolecular Sciences, Macquarie University, New South Wales 2109, Australia.
21 Ecosystèmes Lagunaires, Université Montpellier II, F-34095 Montpellier Cedex 05, France.
22 Department of Biology, University of Miami, Miami, FL 33149, USA.
23 Department of Genetics, Erasmus Medical Center, Rotterdam 3015 CE, Netherlands.
