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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.

SUBMITTER: Leliaert F

PROVIDER: S-EPMC4860620 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.

Leliaert Frederik F Tronholm Ana A Lemieux Claude C Turmel Monique M DePriest Michael S MS Bhattacharya Debashish D Karol Kenneth G KG Fredericq Suzanne S Zechman Frederick W FW Lopez-Bautista Juan M JM

Scientific reports 20160509

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 ...[more]

PMID: 27157793

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Project description:BackgroundThe green algae represent one of the most successful groups of photosynthetic eukaryotes, but compared to their land plant relatives, surprisingly little is known about their evolutionary history. This is in great part due to the difficulty of recognizing species diversity behind morphologically similar organisms. The Trebouxiophyceae is a species-rich class of the Chlorophyta that includes symbionts (e.g. lichenized algae) as well as free-living green algae. Members of this group display remarkable ecological variation, occurring in aquatic, terrestrial and aeroterrestrial environments. Because a reliable backbone phylogeny is essential to understand the evolutionary history of the Trebouxiophyceae, we sought to identify the relationships among the major trebouxiophycean lineages that have been previously recognized in nuclear-encoded 18S rRNA phylogenies. To this end, we used a chloroplast phylogenomic approach.ResultsWe determined the sequences of 29 chlorophyte chloroplast genomes and assembled amino acid and nucleotide data sets derived from 79 chloroplast genes of 61 chlorophytes, including 35 trebouxiophyceans. The amino acid- and nucleotide-based phylogenies inferred using maximum likelihood and Bayesian methods and various models of sequence evolution revealed essentially the same relationships for the trebouxiophyceans. Two major groups were identified: a strongly supported clade of 29 taxa (core trebouxiophyceans) that is sister to the Chlorophyceae + Ulvophyceae and a clade comprising the Chlorellales and Pedinophyceae that represents a basal divergence relative to the former group. The core trebouxiophyceans form a grade of strongly supported clades that include a novel lineage represented by the desert crust alga Pleurastrosarcina brevispinosa. The assemblage composed of the Oocystis and Geminella clades is the deepest divergence of the core trebouxiophyceans. Like most of the chlorellaleans, early-diverging core trebouxiophyceans are predominantly planktonic species, whereas core trebouxiophyceans occupying more derived lineages are mostly terrestrial or aeroterrestrial algae.ConclusionsOur phylogenomic study provides a solid foundation for addressing fundamental questions related to the biology and ecology of the Trebouxiophyceae. The inferred trees reveal that this class is not monophyletic; they offer new insights not only into the internal structure of the class but also into the lifestyle of its founding members and subsequent adaptations to changing environments.

Dataset Information

Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.

Publications

Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.

Similar Datasets

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