Genomic Studies of Blue-Light Signaling Pathways Controlling Seedling Growth

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A detailed description of the mechanisms plants use to sense and respond to their light environment is necessary for a complete understanding of plant development, which is important to those concerned with the practical uses of plants in agriculture and biotechnology as well as to academic researchers. The processes that control the growth of seedlings exposed to blue light do not function properly in Arabidopsis thaliana mutants that lack the cryptochrome photoreceptors. Understanding the molecular-level differences responsible for the differences in growth rates between the wild-type and cryptochrome mutant seedlings will lead to a better understanding of what controls the fundamental process of plant growth. The funding provided by this award will enable measurements of the expression levels of thousands of genes at once using DNA microarray technology at a point during the seedling's response to light that previous work has shown to be critical. Those genes found to differ in expression will be manipulated to test the hypothesis that they function in growth control. Finding genes that affect the rate of seedling growth in specific light conditions could provide plant breeders and biotechnologists with promising targets for their studies. In addition to such a genomic approach, specific hypotheses about the role of the hormone gibberellic acid in the phenomenon of blue-light controlled growth will be tested. Also, the role of calcium in the earliest phase of the response, which is mediated by the phototropin 1 photoreceptor, will be investigated using cell biological techniques.A central theme in the experimental design is that a detailed understanding of the biology under study should guide the genomics experiments, the results of which should be brought back to the biological system for validation. The cycle can then be repeated. In this iterative fashion, a very detailed, molecular-level description of how light controls growth can be obtained during the next funding cycle. In the process, undergraduate, graduate, and postdoctoral students will receive training in modern biological research, which adds to the country's scientific infrastructure.