Journal of Plant Research

, Volume 131, Issue 5, pp 735–746 | Cite as

Identification of a new mating group and reproductive isolation in the Closterium peracerosum–strigosum–littorale complex

  • Yuki TsuchikaneEmail author
  • Hiroka Kobayashi
  • Machi Kato
  • Juri Watanabe
  • Jiunn-Tzong Wu
  • Hiroyuki Sekimoto
Regular Paper


Reproductive isolation is essential for the process of speciation. In order to understand speciation, it is necessary to compare one mating group with other phylogenetically related but reproductively isolated groups. The Closterium peracerosum–strigosum–littorale (C. psl.) complex is a unicellular isogamous zygnematophycean alga, which is believed to share a close phylogenetic relationship with the land plants. In this study, we identified a new mating group, named group G, of C. psl. complex and compared its physiological and biochemical characteristics with the mating group I-E, which was closely related to the mating group G. Zygospores are typically formed as a result of conjugation between mating-type plus (mt+) and mating-type minus (mt) cells in the same mating group during sexual reproduction. Crossing experiments revealed mating groups G and I-E were reproductively isolated from each other, but the release of lone protoplasts from mt cells of mating group G was induced in the presence of mt+ cells of mating group I-E. In fact, the sex pheromone, protoplast-release-inducing protein of mating group I-E induced the release of protoplasts from mt cells of mating group G. When mt+ and mt cells of both mating groups I-E and G were co-cultured (multiple-choice matings), the zygospore formation of mating group G, but not that of mating group I-E, was inhibited. Based on these results, we propose a possible mechanism of reproductive isolation between the two mating groups and suggest the presence of sexual interference between mating group G and mating group I-E.


Alga Closterium Mating group Reproductive isolation Sex pheromone Speciation 



We thank Yukako Kurihara and Atsushi Ono for their support in sample collection in Asahata, Japan. This work was supported by the Grants-in-Aid for Scientific Research (nos. 24370038, 26650147, 15H05237, 16H02518, 16H06378, 16H06279, and 16H04836 to H.S. and 26440223 to Y.T.) from the Japan Society for the Promotion of Science.

Supplementary material

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Supplementary material 1 (PDF 355 KB)


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Copyright information

© The Botanical Society of Japan and Springer Japan KK, part of Springer Nature 2018

Authors and Affiliations

  • Yuki Tsuchikane
    • 1
    Email author
  • Hiroka Kobayashi
    • 2
  • Machi Kato
    • 1
  • Juri Watanabe
    • 1
  • Jiunn-Tzong Wu
    • 3
  • Hiroyuki Sekimoto
    • 1
    • 2
  1. 1.Department of Chemical and Biological Sciences, Faculty of ScienceJapan Women’s UniversityTokyoJapan
  2. 2.Division of Material and Biological Sciences, Graduate School of ScienceJapan Women’s UniversityTokyoJapan
  3. 3.Research Center of BiodiversityAcademia SinicaTaipeiTaiwan

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