Journal Article

Control of Nodule Number by the Phytohormone Abscisic Acid in the Roots of Two Leguminous Species

Akihiro Suzuki, Mitsumi Akune, Mari Kogiso, Yoshihiro Imagama, Ken-ichi Osuki, Toshiki Uchiumi, Shiro Higashi, Sun-Young Han, Shigeo Yoshida, Tadao Asami and Mikiko Abe

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 7, pages 914-922
Published in print July 2004 | ISSN: 0032-0781
Published online July 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch107
Control of Nodule Number by the Phytohormone Abscisic Acid in the Roots of Two Leguminous Species

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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The effects of the phytohormone abscisic acid (ABA) on plant growth and root nodule formation were analyzed in Trifolium repense (white clover) and Lotus japonicus, which form indeterminate and determinate nodules, respectively. In T. repense, although the number of nodules formed after inoculation with Rhizobium leguminosarum bv. trifolii strain 4S (wild type) was slightly affected by exogenous ABA, those formed by strain H1(pC4S8), which forms ineffective nodules, were dramatically reduced 28 days after inoculation (DAI). At 14 and 21 DAI, the number of nodules formed with the wild-type strain was decreased by exogenous ABA. In L. japonicus, the number of nodules was also reduced by ABA treatment. Thus, exogenous ABA inhibits root nodule formation after inoculation with rhizobia. Observation of root hair deformation revealed that ABA blocked the step between root hair swelling and curling. When the ABA concentration in plants was decreased by using abamine, a specific inhibitor of 9-cis-epoxycarotenoid dioxygenase, the number of nodules on lateral roots of abamine-treated L. japonicus increased dramatically, indicating that lower-than-normal concentrations of endogenous ABA enhance nodule formation. We hypothesize that the ABA concentration controls the number of root nodules.

Keywords: Keywords: Abscisic acid — Autoregulation — Lotus japonicus — Nodulation — Symbiosis — Trifolium repense.; Abbreviation: DAI, days after inoculation.

Journal Article.  5285 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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