Three ancient hormonal cues co-ordinate shoot branching in a moss

Authors: Yoan Coudert, Wojtek Palubicki, Karin Ljung, Ondrej Novak, Ottoline Leyser, C Jill Harrison

Abstract

Shoot branching is a primary contributor to plant architecture, evolving independently in flowering plant sporophytes and moss gametophytes. Mechanistic understanding of branching is largely limited to flowering plants such as Arabidopsis, which have a recent evolutionary origin. We show that in gametophytic shoots of Physcomitrella, lateral branches arise by re-specification of epidermal cells into branch initials. A simple model co-ordinating the activity of leafy shoot tips can account for branching patterns, and three known and ancient hormonal regulators of sporophytic branching interact to generate the branching pattern- auxin, cytokinin and strigolactone. The mode of auxin transport required in branch patterning is a key divergence point from known sporophytic pathways. Although PIN-mediated basipetal auxin transport regulates branching patterns in flowering plants, this is not so in Physcomitrella, where bi-directional transport is required to generate realistic branching patterns. Experiments with callose synthesis inhibitors suggest plasmodesmal connectivity as a potential mechanism for transport.

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@article{Coudert:2015:HormonalCues,
  author    = {Yoan Coudert and Wojtek Palubicki and Karin Ljung and Ondrej Novak and Ottoline Leyser and C Jill Harrison},
  title     = {Three ancient hormonal cues co-ordinate shoot branching in a moss},
  journal   = {Elife},
  year      = {2015},
  volume    = {4},
  pages     = {e06808},
  doi       = {10.7554/eLife.06808}
}