The Origin of Chlorarachniophyte Plastids, as Inferred from Phylogenetic Comparisons of Amino Acid Sequences of EF-Tu |
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Authors: | Ken-ichiro Ishida Ying Cao Masami Hasegawa Norihiro Okada Yoshiaki Hara |
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Institution: | (1) Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226, Japan, JP;(2) The Institute of Statistical Mathematics, 4-6-7 Minami-Azabu, Minato-ku, Tokyo 106, Japan, JP;(3) Department of Biology, Faculty of Science, Yamagata University, Kojirakawa, Yamagata 990, Japan, JP |
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Abstract: | A molecular phylogenetic analysis of elongation factor Tu (EF-Tu) proteins from plastids was performed in an attempt to identify
the origin of chlorarachniophyte plastids, which are considered to have evolved from the endosymbiont of a photosynthetic
eukaryote. Partial sequences of the genes for plastid EF-Tu proteins (1,080–1,089 bp) were determined for three algae that
contain chlorophyll b, namely, Gymnochlora stellata (Chlorarachniophyceae), Bryopsis maxima (Ulvophyceae), and Pyramimonas disomata (Prasinophyceae). The deduced amino acid sequences were used to construct phylogenetic trees of the plastid and bacterial
EF-Tu proteins by the maximum likelihood, the maximum parsimony, and the neighbor joining methods.
The trees obtained in the present analysis suggest that all plastids that contain chlorophyll b are monophyletic and that the chlorarachniophyte plastids are closely related to those of the Ulvophyceae. The phylogenetic
trees also suggest that euglenophyte plastids are closely related to prasinophycean plastids. The results indicate that the
chlorarachniophyte plastids evolved from a green algal endosymbiont that was closely related to the Ulvophyceae and that at
least two secondary endosymbiotic events have occurred in the lineage of algae with plastids that contain chlorophyll b.
Received: 10 March 1997 / Accepted: 28 July 1997 |
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Keywords: | : Chlorarachniophyceae — Endosymbiosis — Origin of plastids — Elongation factor Tu — Protein phylogeny |
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