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PLANT CELL 13 (7): 1639-1652

Copyright © 2001 by the American Society of Plant Physiologists.

Overexpression of the Heterotrimeric G-Protein {alpha}-Subunit Enhances Phytochrome-Mediated Inhibition of Hypocotyl Elongation in Arabidopsis

Haruko Okamotoa, Minami Matsuib, and Xing Wang Denga,1

a Department of Molecular, Cellular, and Developmental Biology, Yale University, 165 Prospect Street, New Haven, Connecticut 06520-8104
b Plant Functional Exploration Team, Plant Functional Genomics Research Group, Genomics Science Center RIKEN, 2-1 Hirosawa, Wako-shi, 351-0001 Saitama, Japan

1 To whom correspondence should be addressed. E-mail xingwang.deng{at}; fax 203-432-3854

Abstract: Plant heterotrimeric G-proteins have been implicated in a number of signaling processes. However, most of these studies are based on biochemical or pharmacological approaches. To examine the role of heterotrimeric G-proteins in plant development, we generated transgenic Arabidopsis expressing the G{alpha} subunit of the heterotrimeric G-protein under the control of a glucocorticoid-inducible promoter. With the conditional overexpression of either the wild type or a constitutively active version of Arabidopsis G{alpha}, transgenic seedlings exhibited a hypersensitive response to light. This enhanced light sensitivity was more exaggerated in a relatively lower intensity of light and was observed in white light as well as far-red, red, and blue light conditions. The enhanced responses in far-red and red light required functional phytochrome A and phytochrome B, respectively. Furthermore, the response to far-red light depended on functional FHY1 but not on FIN219 and FHY3. This dependence on FHY1 indicates that the Arabidopsis G{alpha} protein may act only on a discrete branch of the phytochrome A signaling pathway. Thus, our results support the involvement of a heterotrimeric G-protein in the light regulation of Arabidopsis seedling development.

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