Rhizobial gibberellin negatively regulates host nodule number.
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.
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.|Japan Society for the Promotion of Science, Sakyo-ku, Kyoto, Japan.
Yohei
Y
Tatsukami
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Mitsuyoshi
M
Ueda
D007887:Fabaceae / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*; D005875:Gibberellins / Q000494:pharmacology*; D059128:Mesorhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*; D013559:Symbiosis
D005875:Gibberellins