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DEVELOPMENT AND HORMONE ACTION

Global Identification of DELLA Target Genes during Arabidopsis Flower Development^{1,[C],[W],[OA]}

Department of Biological Sciences, Faculty of Sciences (X.H., L.S., L.Y.C.L., Z.T., J.-H.H., H.Y.), and Temasek Life Sciences Laboratory (X.H., W.-W.H., L.S., L.Y.C.L., H.Y.), National University of Singapore, Singapore 117543

Gibberellin (GA) plays important roles in regulating many aspects of plant development. GA derepresses its signaling pathway by promoting the degradation of DELLA proteins, a family of nuclear growth repressors. Although the floral organ identity is established in flowers of the GA-deficient mutant ga1-3, the growth of all floral organs is severely retarded. In particular, abortive anther development in ga1-3 results in male sterility. Genetic analysis has revealed that various combinations of null mutants of DELLA proteins could gradually rescue floral organ defects in ga1-3 and that RGA is the most important DELLA protein involved in floral organ development. To elucidate the early molecular events controlled by RGA during flower development, we performed whole-genome microarray analysis to identify genes in response to the steroid-inducible activation of RGA in ga1-3 rgl2 rga 35S:RGA-GR. Although DELLA proteins were suggested as transcriptional repressors, similar numbers of genes were down-regulated or up-regulated by RGA during floral organ development. More than one-third of RGA down-regulated genes were specifically or predominantly expressed in stamens. A significant number of RGA-regulated genes are involved in phytohormone signaling or stress response. Further expression analysis through activation of RGA by steroid induction combined with cycloheximide identified eight genes as immediate targets of RGA. In situ hybridization and transgenic studies further showed that the expression pattern and function of several selected genes were consistent with the predictions from microarray analysis. These results suggest that DELLA regulation of floral organ development is modulated by multiple phytohormones and stress signaling pathways.

² These authors contributed equally to the article.

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: Hao Yu (dbsyuhao{at}nus.edu.sg).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.108.121301

^* Corresponding author; e-mail dbsyuhao{at}nus.edu.sg.

Received April 16, 2008; accepted May 20, 2008; published May 23, 2008.

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