Veronica Ongaro

Publications (3)20.59 Total impact

• Source

  Available from: pnas.org

  Article: Control of bud activation by an auxin transport switch.

  Przemyslaw Prusinkiewicz, Scott Crawford, Richard S Smith, Karin Ljung, Tom Bennett, Veronica Ongaro, Ottoline Leyser
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  ABSTRACT: In many plant species only a small proportion of buds yield branches. Both the timing and extent of bud activation are tightly regulated to produce specific branching architectures. For example, the primary shoot apex can inhibit the activation of lateral buds. This process is termed apical dominance and is dependent on the plant hormone auxin moving down the main stem in the polar auxin transport stream. We use a computational model and mathematical analysis to show that apical dominance can be explained in terms of an auxin transport switch established by the temporal precedence between competing auxin sources. Our model suggests a mechanistic basis for the indirect action of auxin in bud inhibition and captures the effects of diverse genetic and physiological manipulations. In particular, the model explains the surprising observation that highly branched Arabidopsis phenotypes can exhibit either high or low auxin transport.
  Proceedings of the National Academy of Sciences 09/2009; 106(41):17431-6. · 9.68 Impact Factor
• Article: Interactions between axillary branches of Arabidopsis.

  Veronica Ongaro, Katherine Bainbridge, Lisa Williamson, Ottoline Leyser
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  ABSTRACT: Studies of apical dominance have benefited greatly from two-branch assays in pea and bean, in which the shoot system is trimmed back to leave only two active cotyledonary axillary branches. In these two-branch shoots, a large body of evidence shows that one actively growing branch is able to inhibit the growth of the other, prompting studies on the nature of the inhibitory signals, which are still poorly understood. Here, we describe the establishment of two-branch assays in Arabidopsis, using consecutive branches on the bolting stem. As with the classical studies in pea and bean, these consecutive branches are able to inhibit one another's growth. Not only can the upper branch inhibit the lower branch, but also the lower branch can inhibit the upper branch, illustrating the bi-directional action of the inhibitory signals. Using mutants, we show that the inhibition is partially dependent on the MAX pathway and that while the inhibition is clearly transmitted across the stem from the active to the inhibited branch, the vascular connectivity of the two branches is weak, and the MAX pathway is capable of acting unilaterally in the stem.
  Molecular plant 03/2008; 1(2):388-400. · 5.55 Impact Factor
• Article: Hormonal control of shoot branching.

  Veronica Ongaro, Ottoline Leyser
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  ABSTRACT: Shoot branching is the process by which axillary buds, located on the axil of a leaf, develop and form new flowers or branches. The process by which a dormant bud activates and becomes an actively growing branch is complex and very finely tuned. Bud outgrowth is regulated by the interaction of environmental signals and endogenous ones, such as plant hormones. Thus these interacting factors have a major effect on shoot system architecture. Hormones known to have a major influence are auxin, cytokinin, and a novel, as yet chemically undefined, hormone. Auxin is actively transported basipetally in the shoot and inhibits bud outgrowth. By contrast, cytokinins travel acropetally and promote bud outgrowth. The novel hormone also moves acropetally but it inhibits bud outgrowth. The aim of this review is to integrate what is known about the hormonal control of shoot branching in Arabidopsis, focusing on these three hormones and their interactions.
  Journal of Experimental Botany 02/2008; 59(1):67-74. · 5.36 Impact Factor