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First published online January 12, 2007; 10.1104/pp.106.092254 Plant Physiology 143:1163-1172 (2007) © 2007 American Society of Plant Biologists DELLAs Contribute to Plant Photomorphogenesis1John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom (P.A., J.B., N.P.H.); The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China (L.L., C.J., X.F.); and Laboratoire de Biologie du Développement des Plantes, 13108 Saint Paul les Durance cedex, France (T.D.)
Plant morphogenesis is profoundly influenced by light (a phenomenon known as photomorphogenesis). For example, light inhibits seedling hypocotyl growth via activation of phytochromes and additional photoreceptors. Subsequently, information is transmitted through photoreceptor-linked signal transduction pathways and used (via previously unknown mechanisms) to control hypocotyl growth. Here we show that light inhibition of Arabidopsis (Arabidopsis thaliana) hypocotyl growth is in part dependent on the DELLAs (a family of nuclear growth-restraining proteins that mediate the effect of the phytohormone gibberellin [GA] on growth). We show that light inhibition of growth is reduced in DELLA-deficient mutant hypocotyls. We also show that light activation of phytochromes promotes the accumulation of DELLAs. A green fluorescent protein (GFP)-tagged DELLA (GFP-RGA) accumulates in elongating cells of light-grown, but not dark-grown, transgenic wild-type hypocotyls. Furthermore, transfer of seedlings from light to dark (or vice versa) results in rapid changes in hypocotyl GFP-RGA accumulation, changes that are paralleled by rapid alterations in the abundance in hypocotyls of transcripts encoding enzymes of GA metabolism. These observations suggest that light-dependent changes in hypocotyl GFP-RGA accumulation are a consequence of light-dependent changes in bioactive GA level. Finally, we show that GFP accumulation and quantitative modulation of hypocotyl growth is proportionate with light energy dose (the product of exposure duration and fluence rate). Hence, DELLAs inhibit hypocotyl growth during the light phase of the day-night cycle via a mechanism that is quantitatively responsive to natural light variability. We conclude that DELLAs are a major component of the adaptively significant mechanism via which light regulates plant growth during photomorphogenesis.
1 This work was supported by funding from the European Union (RTN1–2000–00090 INTEGA), the Biotechnology and Biological Sciences Research Council (Core Strategic grant to the John Innes Centre and response modes grant nos. 208/P18610 and 208/P19972), and the National Natural Science Foundation of China (grant nos. 30525003 and 30521001). 2 Present address: UPR2357, Institut de Biologie Moléculaire des Plantes, 67000 Strasbourg, France. 3 These authors contributed equally to the paper. 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: Nicholas P. Harberd (nicholas.harberd{at}bbsrc.ac.uk). www.plantphysiol.org/cgi/doi/10.1104/pp.106.092254 * Corresponding author; e-mail nicholas.harberd{at}bbsrc.ac.uk; fax 44–1603–450025. Received October 31, 2006; accepted December 20, 2006; published January 12, 2007. This article has been cited by other articles:
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