Mutual dependence of the expression of the cell differentiation regulatory protein HetR and the global nitrogen regulator NtcA during heterocyst development

  title={Mutual dependence of the expression of the cell differentiation regulatory protein HetR and the global nitrogen regulator NtcA during heterocyst development},
  author={Alicia M. Muro-Pastor and Ana Valladares and Enrique Flores and Antonia Herrero},
  journal={Molecular Microbiology},
Heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120 depends on both the global nitrogen regulator NtcA and the cell differentiation regulatory protein HetR, and induction of hetR upon nitrogen step‐down depends on NtcA. The use of two out of the four transcription start points (tsps) described for the hetR gene (those located at positions –728 and –271) was found to be dependent on NtcA, and the use of the tsp located at position –271 was also dependent on HetR. Thus… 

HetR-Dependent and -Independent Expression of Heterocyst-Related Genes in an Anabaena Strain Overproducing the NtcA Transcription Factor

Results show that some NtcA-dependent heterocyst-related genes can be expressed independently of HetR, and this study constructed strains that constitutively express the ntcA gene leading to high levels of NTCA protein irrespective of the nitrogen source.

Temporal and Spatial Regulation of the Four Transcription Start Sites of hetR from Anabaena sp. Strain PCC 7120

The role of regulation of the -271 tsp of hetR in the genetic network that governs heterocyst pattern formation and differentiation is demonstrated.

Ectopic expression of hetP can partially bypass the need for hetR in heterocyst differentiation by Anabaena sp. strain PCC 7120

Results suggest that HetP functions directly downstream of HetR in the regulatory network responsible for heterocyst differentiation, and two of the three identified homologues of hetP found in PCC 7120 partially complemented a heTP‐null mutant.

NtcA-Regulated Heterocyst Differentiation Genes hetC and devB from Anabaena sp. Strain PCC 7120 Exhibit a Similar Tandem Promoter Arrangement

The hetC and devBCA promoter regions exhibit similar tandem promoter arrangements, and a second transcriptional start site located at position -293 that leads to NtcA-dependent, HetR-dependent inducible transcription of het C was identified.

Specific Role of the Cyanobacterial PipX Factor in the Heterocysts of Anabaena sp. Strain PCC 7120

The Anabaena PipX factor shows a spatiotemporal specificity contributing to normal heterocyst function, including full activation of the nitrogenase structural genes and genes of thenitrogenase-protective features of theheterocyst.

NrrA, a nitrogen‐responsive response regulator facilitates heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120

It is concluded that the nrrA gene, which encodes a response regulator of the OmpR family with a DNA‐binding domain, facilitates heterocyst development.

A new player in the regulatory cascade controlling heterocyst differentiation in cyanobacteria

HTP is shown to be able to replace hetR for most of the downstream events required for a functional heterocyst, and the 5′‐flanking region of the hetP gene provides the best‐characterized binding site for the HetR protein so far, a seven‐base pair inverted repeat.

Transcription Activation by NtcA and 2-Oxoglutarate of Three Genes Involved in Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120

A stringent requirement of both NtcA and 2-Oxoglutarate was observed for the detection of open complexes and transcript production at the three investigated promoters, which support a key role for 2-oxoglUTarate in transcription activation in the developing heterocyst.

Elements of the heterocyst-specific transcriptome unravelled by co-expression analysis in Nostoc sp. PCC 7120.

The elements identified here are of interest for understanding cell differentiation, engineering of biological nitrogen fixation or production of O2 -sensitive molecules in cyanobacteria.

In vivo activity of the nitrogen control transcription factor NtcA is subjected to metabolic regulation in Synechococcus sp. strain PCC 7942.

Results indicate in vivo regulation of the activity of NtcA at activation of transcription of nitrogen-regulated genes as a function of the nitrogen status of the cell.



The hetC Gene Is a Direct Target of the NtcA Transcriptional Regulator in Cyanobacterial Heterocyst Development

Activation of expression of hetC during heterocyst development appears thus to be directly operated by NtcA, indicating that HetC is not an NTCA-dependent element required for hetR induction.

Expression of the Anabaena hetR gene from a copper-regulated promoter leads to heterocyst differentiation under repressing conditions

  • W. BuikemaR. Haselkorn
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 2001
The results suggest that although the intracellular concentration of HetR has to be elevated for the differentiation decision, PatA plays a role as well, this role may be in the form of posttranslational modification of HtR, because PatA is a member of the response regulator family of proteins.

Requirement of the regulatory protein NtcA for the expression of nitrogen assimilation and heterocyst development genes in the cyanobacterium Anabaena sp. PCC7120

Results showed that the ntcA gene product, NTCA, is required in Anabaena sp.

Developmental regulation and spatial pattern of expression of the structural genes for nitrogenase in the cyanobacterium Anabaena.

Results provide evidence for a causal relationship between development and transcriptional events in Anabaena and three lines of evidence indicate that the mutant has retained the ability to develop a pattern despite its inability to make heterocysts.

Convergence of two global transcriptional regulators on nitrogen induction of the stress‐acclimation gene nblA in the cyanobacterium Synechococcus sp. PCC 7942

It is shown that, under nitrogen stress, nblA is also regulated by NtcA, the global regulator for nitrogen control, and PnblA‐2 is proposed to represent a novel type of NTCA‐dependent promoter.

Anabaena sp. strain PCC 7120 ntcA gene required for growth on nitrate and heterocyst development

The Anabaena sp. strain PCC 7120 ntcA (bifA) gene encodes a sequence-specific DNA-binding protein, NtcA (BifA, VF1) that interacts with the upstream region of several genes, including glnA, xisA,

The hetF Gene Product Is Essential to Heterocyst Differentiation and Affects HetR Function in the Cyanobacterium Nostoc punctiforme

HetF appears to cooperate with HtR in a positive regulatory pathway and may be required for the increased transcription of hetR and localization of the HetR protein in differentiating heterocysts.

hetC, a gene coding for a protein similar to bacterial ABC protein exporters, is involved in early regulation of heterocyst differentiation in Anabaena sp. strain PCC 7120

Transposon-generated mutant C3 of Anabaena sp. strain PCC 7120 is unable to form heterocysts upon deprivation of combined nitrogen but forms a pattern of spaced, weakly fluorescent cells after 2 days

Identification of the Active Site of HetR Protease and Its Requirement for Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120

Results show the Ser152 is the active site of HetR, a serine-type protease activity required for heterocyst differentiation and might be needed for repression of HtR overproduction under conditions of nitrogen deprivation.

NtcA, a global nitrogen regulator from the cyanobacterium Synechococcus that belongs to the Crp family of bacterial regulators

The gene ntcA is proposed to encode a transcriptional activator of genes subject to nitrogen control in Synechococcus, and of special biological significance, is the presence of a conserved helix‐turn‐helix motif in the sequence close to the C‐terminal end of all the proteins in the family.