Control of Heterocyst Differentiation in Free-Living and Symbiotic Cyanobacteria

点击翻译按钮获取中文摘要

The PI hypothesizes that the mechanisms regulating the differentiation of heterocysts (sites of aerobic N2 fixation by Nostoc sp. differ when Nostoc is in symbiotic association relative to growth in the free-living state. He plans to use physiological and molecular genetics to test the hypothesis with analyses in both free-living and symbiotic growth states. Existing mutants will be complemented by electroporation of genomic DNA after in vitro ligation into a plasmid. Insertional mutagenesis will be used to isolate additional mutants. Interrupted genes will be isolated by rescue of the insertion elements; genomic DNA adjacent to the insertions will be cloned form cosmid libraries and characterized. Transcriptional regulation of glucose-6-phosphate dehydrogenase (zwf) will be analyzed in response to nitrogen deprivation and symbiotic interaction using the recently cloned gene. Insertional mutants of zwf will be used to analyze its role in heterocyst function. Recently identified potential nitrogen and anaerobic regulatory genes will be isolated from cosmid libraries by heterologous hybridization and used to construct insertional mutants in Nostoc for analysis of heterocyst differentiation. The results will lead to an understanding of the environmental signals and mechanisms of regulation of cell differentiation in filamentous cyanobacteria in two different growth states.