title: Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.
abstract: The green plants (Viridiplantae) are an ancient group of eukaryotes comprising two main clades: the Chlorophyta, which includes a wide diversity of green algae, and the Streptophyta, which consists of freshwater green algae and the land plants. The early-diverging lineages of the Viridiplantae comprise unicellular algae, and multicellularity has evolved independently in the two clades. Recent molecular data have revealed an unrecognized early-diverging lineage of green plants, the Palmophyllales, with a unique form of multicellularity, and typically found in deep water. The phylogenetic position of this enigmatic group, however, remained uncertain. Here we elucidate the evolutionary affinity of the Palmophyllales using chloroplast genomic, and nuclear rDNA data. Phylogenetic analyses firmly place the palmophyllalean Verdigellas peltata along with species of Prasinococcales (prasinophyte clade VI) in the deepest-branching clade of the Chlorophyta. The small, compact and intronless chloroplast genome (cpDNA) of V. peltata shows striking similarities in gene content and organization with the cpDNAs of Prasinococcales and the streptophyte Mesostigma viride, indicating that cpDNA architecture has been extremely well conserved in these deep-branching lineages of green plants. The phylogenetic distinctness of the Palmophyllales-Prasinococcales clade, characterized by unique ultrastructural features, warrants recognition of a new class of green plants, Palmophyllophyceae class. nov.
authors.affiliation: Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35484-0345, USA.|Department of Biology, Ghent University, 9000 Ghent, Belgium.
authors.forename: Frederik
authors.initials: F
authors.lastname: Leliaert
authors.affiliation: Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35484-0345, USA.|Southeast Environmental Research Center, Florida International University, Miami, FL 33199, USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Tronholm
authors.affiliation: Institut de biologie intégrative et des systèmes, Département de biochimie, de microbiologie et de bio-informatique, Université Laval, Québec (QC) Canada.
authors.forename: Claude
authors.initials: C
authors.lastname: Lemieux
authors.affiliation: Institut de biologie intégrative et des systèmes, Département de biochimie, de microbiologie et de bio-informatique, Université Laval, Québec (QC) Canada.
authors.forename: Monique
authors.initials: M
authors.lastname: Turmel
authors.affiliation: Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35484-0345, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: DePriest
authors.affiliation: Department of Ecology, Evolution and Natural Resources and Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
authors.forename: Debashish
authors.initials: D
authors.lastname: Bhattacharya
authors.affiliation: Lewis B. and Dorothy Cullman Program for Molecular Systematic Studies, The New York Botanical Garden, Bronx, New York 10458, USA.
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Karol
authors.affiliation: Department of Biology, University of Louisiana at Lafayette, LA 70504-3602, USA.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Fredericq
authors.affiliation: College of Natural Resources and Sciences, Humboldt State University, Arcata, CA 95521, USA.
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Zechman
authors.affiliation: Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35484-0345, USA.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Lopez-Bautista
mesh_terms: D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D000460:Chlorophyta / Q000145:classification / Q000235:genetics*; D002874:Chromosome Mapping; D018742:DNA, Chloroplast / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D019143:Evolution, Molecular; D017343:Genes, Plant; D054628:Genome, Chloroplast; D010802:Phylogeny
chemical_list: D018742:DNA, Chloroplast; D004275:DNA, Ribosomal