“MIDORIKO” in green algal cells: the first molecular identification of rickettsial endosymbiotic bacteria infecting plant cells
The endosymbiosis (long-term living of organisms in the cells of different species) is considered to make great contributions to the establishment of mitochondoria in our eukaryotic cells. However, no detailed information about the endosymbiosis has been revealed. Here, we succeed a molecular identification of bacterial endosymbionts, which were firstly found in 1970, within the cells of volvocalean green algae Carteria and Pleodorina. The endosymbionts "MIDORIKO" belong to the family Rickettsiaceae (Rickettsiales, Alphaproteobacteria); this is the first report of rickettsial endosymbionts infecting plant cells. Bacteria belonging to this family are mainly associated with arthropod hosts (e.g. insects or ticks), and some of them are human-pathogenic species that cause dangerous diseases. However, "MIDORIKO" are hosted by the plant cells and grow without harm to their hosts. Because rickettsias are the closest relatives of mitochondria, our discovery of the harmless rickettsial endosymbionts "MIDORIKO" within the cultured green algal cells will contribute much to medical studies of pathogenic rickettsias and the evolutional studies for incipient stages of mitochondrial endosymbiosis.
Kaoru Kawafune 1, Yuichi Hongoh 2, Takashi Hamaji 3, Hisayoshi Nozaki 1
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
- Department of Biological Sciences, School of Bioscience and Biotechnology, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- Department of Botany, Graduate School of Science, Kyoto University, Oiwake-cho, Kita-shirakawa, Kyoto, Japan
- Molecular Identification of Rickettsial Endosymbionts in the Non-phagotrophic Volvocalean Green Algae.
- PLoS ONE 7(2): e31749.