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We report the draft genome of the black cottonwood tree, Populustrichocarpa. Integration of shotgun sequence assembly with geneticmapping enabled chromosome-scale reconstruction of the genome.More than 45,000 putative protein-coding genes were identified.Analysis of the assembled genome revealed a whole-genome duplicationevent; about 8000 pairs of duplicated genes from that eventsurvived in the Populus genome. A second, older duplicationevent is indistinguishably coincident with the divergence ofthe Populus and Arabidopsis lineages. Nucleotide substitution,tandem gene duplication, and gross chromosomal rearrangementappear to proceed substantially more slowly in Populus thanin Arabidopsis. Populus has more protein-coding genes than Arabidopsis,ranging on average from 1.4 to 1.6 putative Populus homologsfor each Arabidopsis gene. However, the relative frequency ofprotein domains in the two genomes is similar. Overrepresentedexceptions in Populus include genes associated with lignocellulosicwall biosynthesis, meristem development, disease resistance,and metabolite transport.
1 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. 2 Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. 3 Plant Sciences Department, University of Tennessee, TN 37996, USA. 4 Department of Biology, West Virginia University, Morgantown, WV 26506, USA. 5 Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, SE-901 87, Umeå, Sweden. 6 Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. 7 Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. 8 Department of Forest Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. 9 U.S. Department of Energy, Joint Genome Institute, Walnut Creek, CA 94598, USA. 10 Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology (VIB), Ghent University, B-9052 Ghent, Belgium. 11 Genome Sciences Centre, 100-570 West 7th Avenue, Vancouver, BC V5Z 4S6, Canada. 12 Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden. 13 Tree-Microbe Interactions Unit, Institut National de la Recherche Agronomique (INRA)–Université Henri Poincaré, INRA-Nancy, 54280 Champenoux, France. 14 Department of Forestry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. 15 Biotechnology Research Center, School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI 49931, USA. 16 Department of Cell and Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2 Canada. 17 School of Forest Resources and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA. 18 Department of Biology, Institute of Molecular Evolutionary Genetics, and Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA. 19 Architecture et Fonction des Macromolécules Biologiques, UMR6098, CNRS and Universities of Aix-Marseille I and II, case 932, 163 avenue de Luminy, 13288 Marseille, France. 20 Warnell School of Forest Resources, University of Georgia, Athens, GA 30602, USA. 21 Department of Plant Biology, University of Georgia, Athens, GA 30602, USA. 22 School of Forest Resources and Conservation, Genetics Institute, and Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32611, USA. 23 INRA-Orléans, Unit of Forest Improvement, Genetics and Physiology, 45166 Olivet Cedex, France. 24 Center for Integrative Genomics, University of California, Berkeley, CA 94720, USA. 25 Genomics Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. 26 Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA. 27 Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA. 28 The Stanford Human Genome Center and the Department of Genetics, Stanford University School of Medicine, Palo Alto, CA 94305, USA. 29 Institute of Forest Genetics, United States Department of Agriculture, Forest Service, Davis, CA 95616, USA. 30 Federal Research Centre for Forests, Hauptstrasse 7, A-1140 Vienna, Austria. 31 Plant Molecular Biology Laboratory, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland. 32 Department of Biological and Environmental Sciences, University of Helsinki, FI-00014 Helsinki, Finland. 33 Department of Biology, 200014, University of Turku, FI-20014 Turku, Finland. 34 Southern Institute of Forest Genetics, United States Department of Agriculture, Forest Service and Department of Forest Science, Texas A&M University, College Station, TX 77843, USA. 35 Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA. 36 Department of Molecular Sciences and Center of Excellence in Genomics and Bioinformatics, University of Tennessee, Memphis, TN 38163, USA. 37 Southern Institute of Forest Genetics, United States Department of Agriculture, Forest Service, Saucier, MS 39574, USA. 38 Developmental Genetics, University of Tübingen, D-72076 Tübingen, Germany. 39 Department of Biotechnology, KTH, AlbaNova University Center, SE-106 91 Stockholm, Sweden.
These authors contributed equally to this work as second authors.
These authors contributed equally to this work as senior authors.
* To whom correspondence should be addressed. E-mail: gtk{at}ornl.gov
These authors contributed equally to this work as second authors. 
These authors contributed equally to this work as senior authors. 
