In the last decade, the full genome sequence of a number of cyanobacteria became available. While these efforts have rewarded us with a lot of information, they also open the question: "What do all those genes do?" This is especially true in the case of multi gene families were multiple genes code for similar but not identical proteins. The genome of one of those, Nostoc PCC 7120 (a.k.a. Anabaena PCC 7120), an filamentous heterocystous cyanobacteria was published in 2001, and found to contain 5 psbA genes, coding for two versions of D1, the main PSII protein, and 4 psbC genes coding (by sequence analysis) for three different versions of the CP43 protein, believed to be involved in energy transfer from the light harvesting complex to the reaction centre.
The different D1s have been found to express in response to UV light or light intensity. But to date there is no information as to if, when, and where the different genes psbC genes are expressed. A homologous gene, isiA has been found to be expressed under iron stress conditions and to create a ring shaped `light harvesting complex-like¿ structure around PSI. We offer to use a combination of bioinformatics, molecular, biochemical, biophysical and physiological techniques to study the role of the different genes in the psbC family of Nostoc 7120. We will look at expression level in RNA and protein level, at photosynthetic potential, and at the exitonic structure of the light harvesting systems of Nostoc PCC 7120 cells grown under different conditions. We will also compare the above between vegetative cells and heterocysts to test the possibility that an alternative psbC is involved in energy transfer to PSI under diazotrophic conditions.
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