Abstract
Shoot branching patterns result from the spatio-temporal regulation of axillary bud outgrowth. Numerous endogenous, developmental and environmental factors are integrated at the bud and plant levels to determine numbers of growing shoots. Multiple pathways that converge to common integrators are most probably involved. We propose several pathways involving not only the classical hormones auxin, cytokinins and strigolactones, but also other signals with a strong influence on shoot branching such as gibberellins, sugars or molecular actors of plant phase transition. We also deal with recent findings about the molecular mechanisms and the pathway involved in the response to shade as an example of an environmental signal controlling branching. We propose the TEOSINTE BRANCHED1, CYCLOIDEA, PCF transcription factor TB1/BRC1 and the polar auxin transport stream in the stem as possible integrators of these pathways. We finally discuss how modeling can help to represent this highly dynamic system by articulating knowledges and hypothesis and calculating the phenotype properties they imply.
Highlights
The pattern of shoot branching, a major component of plant architecture, results from a complex spatio-temporal regulation of axillary bud outgrowth
Light is a major factor (Leduc et al, 2014); plants modulate bud outgrowth and branch development according to the light parameters they sense, i.e., light intensity—as expressed by the photosynthetic photon flux density (PPFD); light quality—depending on wavelengths and their relative proportions; and the photoperiod—the respective amounts of light and dark in a daily cycle of 24 h (Jackson, 2009)
Among the numerous environmental factors that can influence shoot branching, we focused on shade, an interesting and well-studied example of how light regulates the fate of axillary buds
Summary
Catherine Rameau 1,2*, Jessica Bertheloot 3, Nathalie Leduc 4, Bruno Andrieu 5,6, Fabrice Foucher 3 and Soulaiman Sakr 7. Shoot branching patterns result from the spatio-temporal regulation of axillary bud outgrowth. Developmental and environmental factors are integrated at the bud and plant levels to determine numbers of growing shoots. Multiple pathways that converge to common integrators are most probably involved. We propose several pathways involving the classical hormones auxin, cytokinins and strigolactones, and other signals with a strong influence on shoot branching such as gibberellins, sugars or molecular actors of plant phase transition. We deal with recent findings about the molecular mechanisms and the pathway involved in the response to shade as an example of an environmental signal controlling branching. We propose the TEOSINTE BRANCHED1, CYCLOIDEA, PCF transcription factor TB1/BRC1 and the polar auxin transport stream in the stem as possible integrators of these pathways.
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