  Upon growth on dinitrogen, the filamentous cyanobacterium Nostoc PCC 7120
initiates metabolic and morphological changes. We analyzed the expression of
1249 genes from major metabolic categories under nitrogen fixing and
non-nitrogen fixing growth. The expression data were correlated with potential
target secondary structures, probe GC-content, predicted operon structures, and
nitrogen content of gene products. Of the selected genes, 494 show a more than
2-fold difference in the two conditions analyzed. Under nitrogen-fixing
conditions 465 genes, mainly involved in energy metabolism, photosynthesis,
respiration and nitrogen-fixation, were found to be stronger expressed, whereas
29 genes showed a stronger expression under non-nitrogen fixing conditions.
Analysis of the nitrogen content of regulated genes shows that Nostoc PCC 7120
growing on dinitrogen is freed from any constraints to save nitrogen. For the
first time the expression of high light-induced stress proteins (HLIP-family)
is shown to be linked to the nitrogen availability.

Genomics