Dynamics of transcriptional start site selection during nitrogen stress-induced cell differentiation in Anabaena sp PCC7120

作者：Mitschke Jan; Vioque Agustn; Haas Fabian; Hess Wolfgang R^*; Muro Pastor Alicia M

来源：Proceedings of the National Academy of Sciences, 2011, 108(50): 20130-20135.

DOI：10.1073/pnas.1112724108

The fixation of atmospheric N2 by cyanobacteria is a major source of nitrogen in the biosphere. In Nostocales, such as Anabaena, this process is spatially separated from oxygenic photosynthesis and occurs in heterocysts. Upon nitrogen step-down, these specialized cells differentiate from vegetative cells in a process controlled by two major regulators: NtcA and HetR. However, the regulon controlled by these two factors is only partially defined, and several aspects of the differentiation process have remained enigmatic. Using differential RNA-seq, we experimentally define a genome-wide map of >10,000 transcriptional start sites (TSS) of Anabaena sp. PCC7120, a model organism for the study of prokaryotic cell differentiation and N-2 fixation. By analyzing the adaptation to nitrogen stress, our global TSS map provides insight into the dynamic changes that modify the transcriptional organization at a critical step of the differentiation process. We identify >900 TSS with minimum fold change in response to nitrogen deficiency of eight. From these TSS, at least 209 were under control of HetR, whereas at least 158 other TSS were potentially directly controlled by NtcA. Our analysis of the promoters activated during the switch to N2 fixation adds hundreds of protein-coding genes and noncoding transcripts to the list of potentially involved factors. These data experimentally define the NtcA regulon and the DIF+ motif, a palindrome at or close to position -35 that seems essential for heterocyst-specific expression of certain genes.

• 出版日期2011-12-13