Hybridization between Japanese and North American Chlamydomonas reinhardtii (Volvocales, Chlorophyceae)

Authors

  • Takashi Nakada,

    Corresponding author
    1. Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
    2. Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan
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  • Yudai Tsuchida,

    1. Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
    2. Tsuruoka Chuo High School, Tsuruoka, Yamagata, Japan
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  • Kazuharu Arakawa,

    1. Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
    2. Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan
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  • Takuro Ito,

    1. Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
    2. Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan
    3. PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
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  • Masaru Tomita

    1. Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
    2. Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa, Japan
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  • Communicating editor: H. Sekimoto

Summary

The microalga Chlamydomonas reinhardtii is a model organism whose whole genome has been sequenced. Although considered a cosmopolitan species, only eastern North American isolates of C. reinhardtii were available before 2010, when new Japanese isolates were reported. In the study describing the new Japanese isolates, zygote formation between Japanese and North American strains was shown, but germination was not demonstrated. In this study, the germination of intercontinental hybrid zygotes was examined using wild-type Japanese strains and mutant American strains that cannot utilize nitrate. Several clonal progeny strains were established, and the progeny strains were screened based on mating type and nitrate utilization to confirm their hybrid nature. The establishment of four intercontinental hybrid strains with different phenotypic combinations was confirmed by sequencing mating type-specific and nitrate reductase-related genes. The potential for hybrid formation between Japanese and North American strains suggests the existence of a worldwide mating population of C. reinhardtii.

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