A BRC1-modulated switch in auxin efflux accounts for the competition between Arabidopsis axillary buds
Fig 1
2-node explants capture key properties of bud regulation.
(A) A stem segment with two axillary buds illustrates two regulatory hubs controlling shoot branching (i) local expression of the transcription factor BRC1, a repressor of bud activation, and (ii) systemic regulation of the auxin transport network. A canalization-based model of shoot branching postulates that bud activation requires the establishment of canalized auxin transport from the bud into the main stem, the dynamics of which is influenced by autocatalytic feedback in auxin flow between the bud and the stem, and the relative auxin source and sink strengths of the bud and stem, respectively. The relationship between BRC1- and auxin-transport-mediated regulation is not known. (B) Arabidopsis bud activation occurs in at least two phases: a slow-growing lag phase, then a switch to rapid outgrowth. Typical timescale 10–12 days. Modified from Nahas and colleagues [8]. (C) Diagram illustrating the four possible growth outcomes for bud activation on 2-node explants, and their representation in a Mitchison plot. Mitchison plots present the length of the top bud versus that of the bottom bud over time in each explant. Explants where at least one bud grows are termed active, otherwise, they are inactive. Within active explants, there are three possible outcomes: both buds grow, or only either the top or the bottom bud grows. All graphics were drawn by hand using Adobe Illustrator.
doi: https://doi.org/10.1371/journal.pbio.3003395.g001