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Strigolactone Acts Downstream of Auxin to Regulate Bud Outgrowth in Pea and Arabidopsis
Philip B. Brewer, Elizabeth A. Dun, Brett J. Ferguson, Catherine Rameau and Christine A. Beveridge
Vol. 150, No. 1 (May, 2009), pp. 482-493
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/40537870
Page Count: 12
You can always find the topics here!Topics: Auxins, Peas, Plants, Insulin antibodies, Branching, Plant growth, Decapitation, Cytokinins, Apical dominance, Phenotypes
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During the last century, two key hypotheses have been proposed to explain apical dominance in plants: auxin promotes the production of a second messenger that moves up into buds to repress their outgrowth, and auxin saturation in the stem inhibits auxin transport from buds, thereby inhibiting bud outgrowth. The recent discovery of strigolactone as the novel shootbranching inhibitor allowed us to test its mode of action in relation to these hypotheses. We found that exogenously applied strigolactone inhibited bud outgrowth in pea (Pisum sativum) even when auxin was depleted after decapitation. We also found that strigolactone application reduced branching in Arabidopsis (Arabidopsis thaliana) auxin response mutants, suggesting that auxin may act through strigolactones to facilitate apical dominance. Moreover, strigolactone application to tiny buds of mutant or decapitated pea plants rapidly stopped outgrowth, in contrast to applying N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, which significantly slowed growth only after several days. Whereas strigolactone or NPA applied to growing buds reduced bud length, only NPA blocked auxin transport in the bud. Wild-type and strigolactone biosynthesis mutant pea and Arabidopsis shoots were capable of instantly transporting additional amounts of auxin in excess of endogenous levels, contrary to predictions of auxin transport models. These data suggest that strigolactone does not act primarily by affecting auxin transport from buds. Rather, the primary repressor of bud outgrowth appears to be the auxindependent production of strigolactones.
Plant Physiology © 2009 American Society of Plant Biologists (ASPB)