Journal Article Rhizobial gibberellin negatively regulates host nodule number

Tatsukami, Yohei  ,  Ueda, Mitsuyoshi

6p.Nature Publishing Group , 2016-06-16 , Nature Publishing Group
植物と根粒菌の主従逆転-根粒菌がジベレリンを合成し、宿主の根粒数を制御する仕組みを発見-. 京都大学プレスリリース. 2016-06-16.
In legume–rhizobia symbiosis, the nodule number is controlled to ensure optimal growth of the host. In Lotus japonicus, the nodule number has been considered to be tightly regulated by host-derived phytohormones and glycopeptides. However, we have discovered a symbiont-derived phytohormonal regulation of nodule number in Mesorhizobium loti. In this study, we found that M. loti synthesized gibberellic acid (GA) under symbiosis. Hosts inoculated with a GA-synthesis-deficient M. loti mutant formed more nodules than those inoculated with the wild-type form at four weeks post inoculation, indicating that GA from already-incorporated rhizobia prevents new nodule formation. Interestingly, the genes for GA synthesis are only found in rhizobial species that inhabit determinate nodules. Our findings suggest that the already-incorporated rhizobia perform GA-associated negative regulation of nodule number to prevent delayed infection by other rhizobia.

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