Abstract
Genomic DNA of prokaryotes and plastids exists as nucleoids, which associated proteins play functional roles in the global regulation of such essential DNA functions as replication, recombination, transcription, and protection of DNA against environmental stresses. HU is major nucleoid protein in Anabaena sp. PCC 7120 and conserved in not only prokaryotes but also in plastids of red algae and cryptophyte algae. HU is encoded by the hanA gene in Anabaena sp. PCC 7120, however hanA is mostly uncharacterized about transcriptional regulation. In this works, hanA is expressed mainly in the log phase cells and induced under the low temperature or low nitrate conditions. To make deletion mutants of the hanA genes, we attempted to replace hanA by a homolog of Cyanidioschyzon merolae. We obtained mutant strains that were unable to form heterocysts under low nitrate condition. Role of HU in heterocyst differentiation is discussed.
