Journal Article

The Gravity-Regulated Growth of Axillary Buds is Mediated by a Mechanism Different from Decapitation-Induced Release

Daisuke Kitazawa, Yutaka Miyazawa, Nobuharu Fujii, Atsushi Hoshino, Shigeru Iida, Eiji Nitasaka and Hideyuki Takahashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 6, pages 891-900
Published in print June 2008 | ISSN: 0032-0781
Published online June 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn063
The Gravity-Regulated Growth of Axillary Buds is Mediated by a Mechanism Different from Decapitation-Induced Release

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

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When the upper part of the main shoot of the Japanese morning glory (Pharbitis nil or Ipomoea nil) is bent down, the axillary bud situated on the uppermost node of the bending region is released from apical dominance and elongates. Here, we demonstrate that this release of axillary buds from apical dominance is gravity regulated. We utilized two agravitropic mutants of morning glory defective in gravisensing cell differentiation, weeping (we) and weeping2 (we2). Bending the main shoots of either we or we2 plants resulted in minimal elongation of their axillary buds. This aberration was genetically linked to the agravitropism phenotype of the mutants, which implied that shoot bending-induced release from apical dominance required gravisensing cells. Previous studies have shown that basipetal translocation of auxin from the apical bud inhibits axillary bud growth, whereas cytokinin promotes axillary bud outgrowth. We therefore compared the roles of auxin and cytokinin in bending- or decapitation-induced axillary bud growth. In the wild-type and we plants, decapitation increased cytokinin levels and reduced auxin response. In contrast, shoot bending did not cause significant changes in either cytokinin level or auxin response, suggesting that the mechanisms underlying gravity- and decapitation-regulated release from apical dominance are distinct and unique.

Keywords: Apical dominance; Auxin; Gravitropism; Cytokinin; Morning glory; weeping

Journal Article.  5721 words.  Illustrated.

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

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