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Journal of Molecular Evolution

, Volume 47, Issue 5, pp 544–550 | Cite as

Actin Phylogeny Identifies Mesostigma viride as a Flagellate Ancestor of the Land Plants

  • Debashish  Bhattacharya
  • Klaus  Weber
  • Seon Sook  An
  • Wolfgang  Berning-Koch

Abstract.

Green algae and land plants trace their evolutionary history to a unique common ancestor. This ``green lineage'' is phylogenetically subdivided into two distinct assemblages, the Chlorophyta and the Streptophyta. The Chlorophyta includes the Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Prasinopohyceae, whereas the Streptophyta includes the Charophyceae plus the bryophytes, ferns, and all other multicellular land plants (Embryophyta). The Prasinophyceae is believed to contain the earliest divergences within the green lineage. Phylogenetic analyses using rDNA sequences identify the prasinophytes as a paraphyletic taxon that diverges at the base of the Chlorophyta. rDNA analyses, however, provide ambiguous results regarding the identity of the flagellate ancestor of the Streptophyta. We have sequenced the actin-encoding cDNAs from Scherffelia dubia (Prasinophyceae), Coleochaete scutata, Spirogyra sp. (Charophyceae), and the single-copy actin gene from Mesostigma viride (Prasinophyceae). Phylogenetic analyses show Mesostigma to be the earliest divergence within the Streptophyta and provide direct evidence for a scaly, biflagellate, unicellular ancestor for this lineage. This result is supported by the existence of two conserved actin-coding region introns (positions 20-3, 152-1), and one intron in the 5′-untranslated region of the actin gene shared by Mesostigma and the embryophytes.

Key words: Actin — Chlorophyta — Green algae — Land plants —Mesostigma viride— Phylogeny — Prasinophyceae — Streptophyta 

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Copyright information

© Springer-Verlag New York Inc. 1998

Authors and Affiliations

  • Debashish  Bhattacharya
    • 1
  • Klaus  Weber
    • 2
  • Seon Sook  An
    • 1
  • Wolfgang  Berning-Koch
    • 2
  1. 1.Department of Biological Sciences, University of Iowa, 239 Biology Building, Iowa City, IA 52242-1324, USAUS
  2. 2.Department of Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, GermanyDE

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