EVOLUTIONARY ORIGIN OF GLOEOMONAS (VOLVOCALES,CHLOROPHYCEAE), BASED ON ULTRASTRUCTURE OF CHLOROPLASTS AND MOLECULAR PHYLOGENY1 |
| |
Authors: | Hisayoshi Nozaki Takashi Nakada Shin Watanabe |
| |
Institution: | 1. Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo‐ku, Tokyo 113‐0033, Japan;2. Author for correspondence: e‐mail .;3. Institute for Advanced Biosciences, Keio University, 246‐2 Mizukami, Kakuganji, Tsuruoka, Yamagata 997‐0017, Japan;4. Research Fellow of the Japan Society for the Promotion of Sciences.;5. Department of Biology, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930‐8555, Japan |
| |
Abstract: | Gloeomonas is a peculiar unicellular volvocalean genus because it lacks pyrenoids in the chloroplasts under the light microscope and has two flagellar bases that are remote from each other. However, ultrastructural features of chloroplasts are very limited, and no molecular phylogenetic analyses have been carried out in Gloeomonas. In this study, we observed ultrastructural features of chloroplasts of three species of Gloeomonas and Chloromonas rubrifilum (Korshikov ex Pascher) Pröschold, B. Marin, U. Schlösser et Melkonian SAG 3.85, and phylogenetic analyses were carried out based on the combined data set from 18S rRNA, ATP synthase beta‐subunit, and P700 chl a–apoprotein A2 gene sequences to deduce the natural phylogenetic positions of the genus Gloeomonas. The present EM demonstrated that the chloroplasts of the three Gloeomonas species and C. rubrifilum SAG 3.85 did not have typical pyrenoids with associated starch grains, but they possessed pyrenoid matrices that protruded interiorly within the stroma regions of the chloroplast. The pyrenoid matrices were large and broad in C. rubrifilum, whereas those of the three Gloeomonas species were recognized in only the small protruded regions of the chloroplast lobes. The present multigene phylogenetic analyses resolved that the three species of Gloeomonas belong to the Chloromonas lineage or Chloromonadinia of the Volvocales, and Chloromonas insignis (Anakhin) Gerloff et H. Ettl NIES‐447 and C. rubrifilum SAG 3.85, both of which have pyrenoids without associated starch grains, were positioned basally to the clade composed of the three species of Gloeomonas. Therefore, Gloeomonas might have evolved from such a Chloromonas species through reduction in pyrenoid matrix size within the chloroplast and by separating their two flagellar bases. |
| |
Keywords: | Chloromonadinia Chloromonas evolution Gloeomonas molecular phylogeny pyrenoid ultrastructure Volvocales |
|
|