Abstract
Heterocyst is a terminally differentiated cell, which is specialized in dinitrogen fixation. Heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120 is triggered by deprivation of combined nitrogen in the medium. Although various genes that are upregulated during the heterocyst differentiation have been reported, most studies to date were limited to individual or a small number of genes. Here we report on the genome-wide expression analysis of the response to nitrogen deprivation. Expression pattern of genes upregulated by nitrogen deprivation is classified into three clusters, and it is indicated that extensive changes in gene expression occurred at the eighth hour of nitrogen deprivation. We also noted that many of the upregulated genes were physically clustered to form expressed islands on the chromosome. This suggests that a mechanism of global regulation of gene expression that involves chromosomal structure exists, which is reminiscent of eukaryotic chromatin remodeling.
