Identification of rice Allene Oxide Cyclase mutants and the function of jasmonate for defence against Magnaporthe oryzae

Authors

  • Michael Riemann,

    1. Botanical Institute, Molecular Cell Biology, Karlsruhe Institute of Technology, Karlsruhe, Germany
    2. Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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    • These authors contributed equally to this work.
  • Ken Haga,

    1. Botanical Gardens, Graduate School of Science, Osaka City University, Osaka, Japan
    Current affiliation:
    1. Graduate School of Science and Technology, Niigata University, Niigata, Japan
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    • These authors contributed equally to this work.
  • Takafumi Shimizu,

    1. Biotechnology Research Center, University of Tokyo, Tokyo, Japan
    Current affiliation:
    1. Botanical Gardens, Graduate School of Science, Osaka City University, Osaka, Japan
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    • These authors contributed equally to this work.
  • Kazunori Okada,

    1. Biotechnology Research Center, University of Tokyo, Tokyo, Japan
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  • Sugihiro Ando,

    1. Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
    Current affiliation:
    1. Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
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  • Susumu Mochizuki,

    1. Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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  • Yoko Nishizawa,

    1. Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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  • Utako Yamanouchi,

    1. Rice Applied Genomics Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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  • Peter Nick,

    1. Botanical Institute, Molecular Cell Biology, Karlsruhe Institute of Technology, Karlsruhe, Germany
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  • Masahiro Yano,

    1. Agrigenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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  • Eiichi Minami,

    1. Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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  • Makoto Takano,

    1. Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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  • Hisakazu Yamane,

    1. Biotechnology Research Center, University of Tokyo, Tokyo, Japan
    2. Department of Biosciences, Teikyo University, Utsunomiya, Japan
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  • Moritoshi Iino

    Corresponding author
    1. Botanical Gardens, Graduate School of Science, Osaka City University, Osaka, Japan
    • Botanical Institute, Molecular Cell Biology, Karlsruhe Institute of Technology, Karlsruhe, Germany
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For correspondence (e-mail iino@sci.osaka-cu.ac.jp).

Summary

Two photomorphogenic mutants of rice, coleoptile photomorphogenesis 2 (cpm2) and hebiba, were found to be defective in the gene encoding allene oxide cyclase (OsAOC) by map-based cloning and complementation assays. Examination of the enzymatic activity of recombinant GST–OsAOC indicated that OsAOC is a functional enzyme that is involved in the biosynthesis of jasmonic acid and related compounds. The level of jasmonate was extremely low in both mutants, in agreement with the fact that rice has only one gene encoding allene oxide cyclase. Several flower-related mutant phenotypes were observed, including morphological abnormalities of the flower and early flowering. We used these mutants to investigate the function of jasmonate in the defence response to the blast fungus Magnaporthe oryzae. Inoculation assays with fungal spores revealed that both mutants are more susceptible than wild-type to an incompatible strain of M. oryzae, in such a way that hyphal growth was enhanced in mutant tissues. The level of jasmonate isoleucine, a bioactive form of jasmonate, increased in response to blast infection. Furthermore, blast-induced accumulation of phytoalexins, especially that of the flavonoid sakuranetin, was found to be severely impaired in cpm2 and hebiba. Together, the present study demonstrates that, in rice, jasmonate mediates the defence response against blast fungus.

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