9509229 Honma The long term goal of the proposed research is to understand the developmental changes that occur during the transition from vegetative to reproductive growth in Arabidopsis thaliana. Physiological experiments suggest that environmental as well as endogenous factors regulate the time to flowering. Relatively little is known, however, about the genes and their protein products that are required in this critical transition to the reproductive state. The identification of mutants altered in floral induction and the isolation of the corresponding genes will contribute to the understanding of this complex process. An Ac/Ds transposon system was developed for mutagenesis and gene isolation. This system has been used to generate an early flowering mutant, eaf20, that makes the vegetative to reproductive transition earlier than wild-type plants grown in the same condition. Genetic and molecular experiments indicate that the eaf20 gene is tagged with Ds. The Ds transposon sequences were used to isolate a small segment of the flanking genomic region that encodes the flowering gene. Future experiments will focus on isolation and characterization of genomic and cDNA clones that correspond to the eaf20 gene. Genomic clones covering the eaf20 region will be cloned using the previously isolated Ds flanking sequence. To confirm that the eaf20 gene has been isolated, a complementation experiment will be done in which the genomic clones are introduced into the eaf20 mutant plants and screened for rescue of the mutant phenotype. Sequencing of the genomic copies of the eaf20 gene will provide valuable information regarding regulatory regions of the gene that will be used for subsequent studies. The genomic clones will also be used to isolate eaf20 cDNAs. Sequencing the eaf20 cDNAs will be followed by database searches to look for regions of similarity to genes with known biochemical functions. These molecular studies will lay the foundation for fut ure experiments and will contribute to our understanding of floral induction in Arabidopsis.
