9808823 Cheng The overall research goal of this laboratory is to elucidate the regulatory pathways through which nitrate and light signals act coordinately to regulate nitrate reductase (NR) gene expression. This research program is important to the advancement of science because these regulatory pathways are fundamental to plant growth and development. Nitrate assimilation and photosynthesis are the two most energy-consuming pathways in plant. One way to achieve balance of these two pathways is to place expression of the NR genes under the control of a plant's photosynthesis capacity. Photomorphogenesis during seed germination marks the onset of photosynthesis. Among the regulatory mutants we have isolated that affect NR gene expression, one mutant, cr88, is also defective in photomorphogenesis. This discovery genetically links expression of the NR genes with the photomorphogenic signaling cascade. The research proposed here will 1) determine the growth-stage specific requirement of CR88, 2) position CR88 in the photomorphogenic pathway, 3) isolate additional cr88 mutant alleles and clone the CR88 gene, and 4) elucidate the biochemical and physiological function(s) of CR88. Studies of CR88 will provide insights into the mechanisms by which expression of some of the genes involved in nitrate assimilation and photomorphogenesis is regulated coordinately. This understanding may allow genetic manipulation of crop plants that respond to nitrate and photosynthetic activity optimally for agricultural practices.
