Tai-ping SunDepartment of Biology, Duke University, Durham, NC, USA F1000 Faculty Member (since 14 May 2003)
Professor, Department of Biology
Bioactive gibberellins (GAs) are plant growth hormones, controlling diverse processes such as seed germination, stem elongation, leaf expansion, and flower and fruit development. GA-mediated growth events can be modulated by changing the level of bioactive GAs and/or altering the tissue responsiveness to GAs. To understand the developmental and environmental regulation of GA biosynthesis, we and others have cloned several Arabidopsis genes encoding enzymes that catalyze early and late steps in GA biosynthetic pathway. Their expression patterns suggest that the first gene GA1 may serve as a gate keeper to control the flow of metabolites into the GA pathway, whereas the late genes are important for fine-tuning the amount of active GAs in specific tissues. To monitor the sites of bioactive GA synthesis, we analyzed the developmental expression profiles of the GA3ox genes that encode enzymes for the final step of bioactive GA synthesis. These studies indicate that local GA transport is required to support proper development during reproductive growth. Our previous genetic studies identified DELLA proteins, which are major repressors of GA signaling. GA, upon binding to its receptor GID1, de-represses its signaling pathway by targeting rapid degradation of DELLA, via the SCFSLY1 E3 ubiquitin-26S proteasome pathway. Our biochemical studies and structural analysis of the GA-GID1-DELLA complex reveal the exciting molecular mechanism how GA-GID1 recognizes DELLA. The DELLA proteins are likely nuclear transcriptional regulators, which may control target gene expression via interaction with other transcription factors. Our recent microarray analysis followed by chromatin immunoprecipitation-qPCR (ChIP-qPCR) helped to identify several putative DELLA targets.
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