Overexpression of the heterotrimeric G-protein ?-subunit enhances phytochrome-mediated inhibition of hypocotyl elongation in Arabidopsis

Okamoto, Haruko, Matsui, Minami and Wang Deng, Xing (2001) Overexpression of the heterotrimeric G-protein ?-subunit enhances phytochrome-mediated inhibition of hypocotyl elongation in Arabidopsis. The Plant Cell, 13 (7), 1639-1652. (doi:10.1105/tpc.13.7.1639). (PMID:11449056)

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? 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?, 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? 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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