Signal Transduction Protein P _II Is Required for NtcA-Regulated Gene Expression during Nitrogen Deprivation in the Cyanobacterium Synechococcus elongatus Strain PCC 7942

Abstract

The transcription factor of the cyclic AMP receptor protein/FNR family, NtcA, and the P II signaling protein play central roles in global nitrogen control in cyanobacteria. A dependence on P II for NtcA-regulated transcription, however, has not been observed. In the present investigation, we examined alterations in gene expression following nitrogen deprivation in Synechococcus elongatus strain PCC 7942 and specifically the roles of NtcA and P II . Global changes in de novo protein synthesis following combined-nitrogen deprivation were visualized by in vivo [35 S]methionine labeling and two-dimensional polyacrylamide gel electrophoresis analysis. Nearly all proteins whose synthesis responded specifically to combined-nitrogen deprivation in wild-type cells of S. elongatus failed to respond in P II -and NtcA-deficient mutants. One of the proteins whose synthesis was down-regulated in a P II -and NtcA-dependent manner was RbcS, the small subunit of RubisCO. Quantification of its mRNA revealed that the abundance of the rbcLS transcript following combined-nitrogen deprivation rapidly declined in wild-type cells but not in P II and NtcA mutant cells. To investigate further the relationship between P II and NtcA, fusions of the promotorless luxAB reporter genes to the NtcA-regulated glnB gene were constructed and these constructs were used to transform wild-type cells and P II ؊ and NtcA ؊ mutants. Determination of bioluminescence under different growth conditions showed that NtcA represses gene expression in the presence of ammonium in a P II -independent manner. By contrast, NtcA-dependent activation of glnB expression following combined-nitrogen deprivation was impaired in the absence of P II . Together, these results suggest that under conditions of combined-nitrogen deprivation, the regulation of NtcA-dependent gene expression requires the P II signal transduction protein.

SigC, the Group 2 Sigma Factor of RNA Polymerase, Contributes to the Late-stage Gene Expression and Nitrogen Promoter Recognition in the CyanobacteriumSynechocystissp. Strain PCC 6803

“…49) NtcA-dependent gene expression requires the GlnB signal transduction protein. 50) On the other hand, a recent study revealed that cyanobacteria perceive nitrogen status by sensing intracellular 2-oxoglutarate (2-OG) levels 51) and that the binding of NtcA to glnA and ntcA promoters of Synechococcus PCC 7942 in vitro has been shown to be increased by 2-OG.…”

Identification of PamA as a PII-binding Membrane Protein Important in Nitrogen-related and Sugar-catabolic Gene Expression in Synechocystis sp. PCC 6803

“…Aldehni et al (18) also revealed that PII was involved in regulating the in vivo activity of the NtcA regulons in Synechococcus sp. PCC 7942 (18). However, the underlying mechanism for this PII function also remains unclear.…”

Complex Formation and Catalytic Activation by the PII Signaling Protein of N-Acetyl-l-glutamate Kinase from Synechococcus elongatus Strain PCC 7942

“…strain PCC 6803 cells is catalyzed by a PP2C homologue protein phosphatase, termed PphA (28). Dephosphorylation of P II -P by PphA is controlled by the effector molecules binding to P II -P. 2-Oxoglutarate in synergy with ATP leads to a strong inhibition of dephosphorylation, whereas ADP has a partial inhibitory effect (29,30).Unlike in proteobacteria, receptors of P II signaling have not been known at the molecular level in cyanobacteria, although physiological studies suggested P II to be involved in the regulation of nitrite/nitrate transport (11) and the global transcriptional activator NtcA under conditions of nitrogen deprivation (31,32). Recently, the first cellular component regulated by PII could be identified in S. elongatus (33).…”

“…Unlike in proteobacteria, receptors of P II signaling have not been known at the molecular level in cyanobacteria, although physiological studies suggested P II to be involved in the regulation of nitrite/nitrate transport (11) and the global transcriptional activator NtcA under conditions of nitrogen deprivation (31,32). Recently, the first cellular component regulated by PII could be identified in S. elongatus (33).…”