Molecular Control of Ovule Development

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0079434GasserAs the precursors to seeds, ovules play essential roles in sexual plant reproduction and crop productivity. Because ovule development includes processes which typify development in all multicellular organisms, it can serve as a model for studying fundamental mechanisms regulating the processes of morphogenesis and tissue differentiation. Genes regulating critical steps in ovule development have been identified through studies on mutations affecting this process in Arabidopsis thaliana. Three mutants affecting growth of ovules, or specific substructures, will be used to elucidate the regulation of ovule development. HUELLENLOS (HLL) is essential for maintenance of ovule growth, and SHORT INTEGUMENTS 2 (SIN2) and INNER NO OUTER (INO) are essential for complete formation of the integuments (which go on to form the seed coat). INO encodes a putative transcription factor and exhibits a tightly regulated pattern of expression in ovules. The mechanism of INO regulation will be examined by dissecting the regulatory elements in the promoter region, and by testing such elements for interactions with putative regulators of this gene. HLL encodes a protein with significant similarity to the L14 subunits of bacterial ribosomes. mRNA and protein localizations will be used to determine the expression pattern and subcellular location of the protein product of this gene. These studies will test the hypotheses that HLL has an essential cellular role, or that it is a novel regulator of ovule development. Following isolation, the SIN2 gene will be subject to similar analysis. DNA microarrays will be tested with probes deriving from mutant tissues to assess the utility of this method in evaluation of overall patterns of gene expression in ovules and integuments. Completion of the proposed research will significantly increase our understanding of genetic and molecular control of plant reproductive development and of morphogenesis and histogenesis in general.