Molecular and Genetic Analysis of COP9, A Regulatory Component Involved in Light-Controlled Development in Arabidopsis

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9303029 Deng Light signals from the environment are perceived by specific regulatory photoreceptors in plants and transduced by unknown mechanisms to control growth and development. The long term goal of this research is to dissect the molecular mechanisms by which such signals are transduced and integrated to modulate plant development. The light-regulated seedling development of Arabidopsis thaliana has been used as a model experimental system in my laboratory. Nine COP (constitutive photomorphogenic) loci, which when mutated produce dark-grown seedlings with a morphology resembling that of light-grown wild-type seedlings, have been identified. The Arabidopsis COP1 (constitutive photomorphogenic) locus, which plays a central role in the light signaling process and encodes a novel protein with putative DNA-binding and G-protein homology domains, represents the only light signaling component besides phytochrome that has been characterized in a molecular term. The preliminary studies in my laboratory indicate that the cop9 mutation results in the same range of phenotype as the cop1 mutants. Therefore COP9 and COP1 may encode closely related regulatory components in the same signaling pathway. It is proposed here to clone and sequence the COP9 locus, by using an available T-DNA insertional mutant allele. After determining the molecular identity of the COP9 gene, appropriate probes (DNA and antibodies) will be developed for the molecular analysis and COP9 promoter-GUS transgenic plants will be generated for analyzing expression pattern of the COP9 gene. With these tools available, it will enable us to determine at the molecular level 1) how the wild-type COP9 gene product couples light signals and seedling development, and 2) the relationship between the COP1 and COP9 genes. Furthermore, the regulatory hierarchy of COP9 and other identified photomorphogenic loci during light-regulated seedling development will be analyzed. %%% Accomplishment of these studies will not only ascertain the nature of a critical regulatory component that links light signals to seedling development, but also provide clues as to how the COP9 relates to other photomorphogenic genes. ***