Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 111, Issue 16, Pages 6092-6097Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1322045111
Keywords
shoot branching; sink demand; decapitation; girdling; long-distance signaling
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Funding
- Australian Research Council [DP110100808]
- US Department of Energy through its Office of Biological and Environmental Research [DE-AC02-98CH10886]
- Goldhaber Distinguished Fellowship
- Australian Research Council Future Fellowship [FT100100806]
- Australian Research Council [FT100100806] Funding Source: Australian Research Council
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For almost a century the plant hormone auxin has been central to theories on apical dominance, whereby the growing shoot tip suppresses the growth of the axillary buds below. According to the classic model, the auxin indole-3-acetic acid is produced in the shoot tip and transported down the stem, where it inhibits bud growth. We report here that the initiation of bud growth after shoot tip loss cannot be dependent on apical auxin supply because we observe bud release up to 24 h before changes in auxin content in the adjacent stem. After the loss of the shoot tip, sugars are rapidly redistributed over large distances and accumulate in axillary buds within a timeframe that correlates with bud release. Moreover, artificially increasing sucrose levels in plants represses the expression of BRANCHED1 (BRC1), the key transcriptional regulator responsible for maintaining bud dormancy, and results in rapid bud release. An enhancement in sugar supply is both necessary and sufficient for suppressed buds to be released from apical dominance. Our data support a theory of apical dominance whereby the shoot tip's strong demand for sugars inhibits axillary bud outgrowth by limiting the amount of sugar translocated to those buds.
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