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First published online September 15, 2006; 10.1104/pp.106.087676 Plant Physiology 142:1014-1026 (2006) © 2006 American Society of Plant Biologists Branching Genes Are Conserved across Species. Genes Controlling a Novel Signal in Pea Are Coregulated by Other Long-Distance Signals1Station de Génétique et d'Amélioration des Plantes, Institut J.P. Bourgin, Institut National de la Recherche Agronomique, 78026 Versailles, France (X.J., M.G., K.H., C.R.); and Australian Research Council Centre of Excellence for Integrative Legume Research and School of Integrative Biology, University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia (T.B., E.A.D., C.A.B.)
Physiological and genetic studies with the ramosus (rms) mutants in garden pea (Pisum sativum) and more axillary shoots (max) mutants in Arabidopsis (Arabidopsis thaliana) have shown that shoot branching is regulated by a network of long-distance signals. Orthologous genes RMS1 and MAX4 control the synthesis of a novel graft-transmissible branching signal that may be a carotenoid derivative and acts as a branching inhibitor. In this study, we demonstrate further conservation of the branching control system by showing that MAX2 and MAX3 are orthologous to RMS4 and RMS5, respectively. This is consistent with the long-standing hypothesis that branching in pea is regulated by a novel long-distance signal produced by RMS1 and RMS5 and that RMS4 is implicated in the response to this signal. We examine RMS5 expression and show that it is more highly expressed relative to RMS1, but under similar transcriptional regulation as RMS1. Further expression studies support the hypothesis that RMS4 functions in shoot and rootstock and participates in the feedback regulation of RMS1 and RMS5 expression. This feedback involves a second novel long-distance signal that is lacking in rms2 mutants. RMS1 and RMS5 are also independently regulated by indole-3-acetic acid. RMS1, rather than RMS5, appears to be a key regulator of the branching inhibitor. This study presents new interactions between RMS genes and provides further evidence toward the ongoing elucidation of a model of axillary bud outgrowth in pea.
1 This work was supported by FP6 Project Grain Legumes (FOOD–CT–2004–506223), Institut National de la Recherche Agronomique, and Région Ile de France, by the Australian Research Council, and by Australian postgraduate awards (to T.B. and E.A.D.). The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Catherine Rameau (rameau{at}versailles.inra.fr). www.plantphysiol.org/cgi/doi/10.1104/pp.106.087676 * Corresponding author; e-mail rameau{at}versailles.inra.fr; fax 33–1–30–83–33–19. Received July 31, 2006; accepted September 4, 2006; published September 15, 2006. This article has been cited by other articles:
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