9407920 Brusslan This is a Research Planning Grant. The objective are to: 1, isolate virescent mutants from EMS, fast-neutron, and T- DNA mutagenized Arabidopsis; 2, characterize the development of the photosynthetic apparatus in these mutants using absorption spectroscopy, fluorescence emission, transmission electron microscopy, and native Deriphat gel electrophoresis; 3, to analyze mutants with regard to temperature sensitivity as well as sensitivity to differing light intensities; and 4, to perform a genetic analysis. The genetic analysis will include reciprocal backcrosses to determine if mutations are inherited maternally or through either parent, complementation studies between the different mutant lines, and crosses between mutant lines and a wild type line of a different ecotype to permit RFLP mapping. The long term goal is to clone and characterize genes whose products are involved in the regulation of chloroplast development in higher plants. %%% The chloroplast is the site of photosynthesis and carbon fixation, and its development is critical for plant survival. The chloroplast originated as an endosymbiont of photosynthetic bacteria, and over time many regulatory functions of the bacterial genome wre taken over by the nucleus. Although many mutations that alter the chloroplast have been isolated from a large number of different plant species, none so far have led to clear understanding of the molecular events that regulate chloroplast development in higher plants. The model plant system, Arabidopsis thaliana, offers an opportunity to understand this process because genes involved in plastid development that are identified by mutation can be cloned. The objective of the work proposed in this research planning grant is to isolate mutants in Arabidopsis that display a delay in greening phenotype (termed virescent) in order to evaluate mutations most likely to be involved in the regulation of chloroplast development. Several mutants have alr eady been obtained, and more will be obtained. These will be characterized biochemically, structurally, and genetically in order to identify those of the greatest potential for understanding chloroplast development. The long term goal of this work is to clone the genes responsible for these mutations and to understand their functions. ***
