The plant hormone auxin controls many processes in growth and development, and acts at the cell level by promoting division or elongation. In cultures, auxin is essential for division, specifically for progression into S phase and mitosis. AUX/IAA proteins are negative regulators of many auxin responsive genes, and are destroyed in response to auxin. However, little is known of auxin action in the cell cycle nor if AUX/IAA are involved. Here we propose to analyse how auxin regulates cell cycle progression u sing a synchronisable cell system for Arabidopsis unique to the host lab allowing the use of microarray approaches, for which a large expression database is available in the host. Three likely possible mechanisms of auxin control at the G1/S and G2/M bound aries will be investigated. Transcriptional targets for auxin amongst core cell cycle regulators will be identified. We will then test whether AUX/IAA proteins are involved in regulation of these genes either directly or indirectly, by making transgenic c ell lines inducibly expressing dominant gain- or loss-of-function AUX/IAA mutants and assessing effects on cell cycle progression and gene expression. Finally whether auxin triggers proteolysis of negative cell cycle regulators will be tested. These experi ments will be carried out in synchronised cells in G1 and G2 to establish common and distinct mechanisms. The results will throw important new light on how auxin controls cell division, and hence impact on our understanding of this key plant hormone in dev elopment. During the project, the candidate will gain valuable scientific and professional training in the host laboratory. The candidate will contribute to the host by sharing his expertise and skills he gained during his scientific career. The Fellowship will also contribute significantly to the European research excellence by establishing collaborations with world leading research groups in auxin biology.
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