Abstract
We have investigated the gene expression profile using a DNA microarray when the cells of Anabaena sp. PCC 7120 were exposed to certain stress conditions. Nitrogen depleted conditions caused an induction of "Nif gene islands". Those gene expression are mediated by a transcription factor, NrrA which is under the control of global nitrogen-responsive transcription factor, NtcA. NrrA regulates HetR which is a master transcription factor for nitrogen metabolic genes. A terrestrial cyanobacterium, Nostoc sp. HK-01 shows a high drought stress tolerance. We have found that a sigma factor, SigI, plays a key role in the cellular response to desiccation stress. It was also found that the genes involved in treharose metabolism were induced by desiccation stress. As for salt stress, a transcription factor, OrrA, was found to be important to regulate gene expression in response to high salt concentration. However, the regulatory mechanism by OrrA has not yet been elucidated.
