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Nitrogen Starvation Acclimation in Synechococcus elongatus: Redox-Control and the Role of Nitrate Reduction as an Electron Sink.

Klotz A, Reinhold E, Doello S, Forchhammer K - Life (Basel) (2015)

Bottom Line: This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation.This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors.It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction.

View Article: PubMed Central - PubMed

Affiliation: Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany. alexander.klotz@uni-tuebingen.de.

ABSTRACT
Nitrogen starvation acclimation in non-diazotrophic cyanobacteria is characterized by a process termed chlorosis, where the light harvesting pigments are degraded and the cells gradually tune down photosynthetic and metabolic activities. The chlorosis response is governed by a complex and poorly understood regulatory network, which converges at the expression of the nblA gene, the triggering factor for phycobiliprotein degradation. This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation. Inhibition of glutamine synthetase (GS) by a precise dosage of l-methionine-sulfoximine (MSX) mimics the metabolic situation of nitrogen starvation. Addition of nitrate to such MSX-inhibited cells eliminates the associated redox-stress by enabling electron flow towards nitrate/nitrite reduction and thereby, prevents the induction of nblA expression and the associated chlorosis response. This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors. It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction.

No MeSH data available.


Related in: MedlinePlus

Expression of the glnB::luxAB reporter gene within 5 h after MSX addition at concentrations indicated using the FAM2 reporter strain and measuring luciferease activity.
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life-05-00888-f003: Expression of the glnB::luxAB reporter gene within 5 h after MSX addition at concentrations indicated using the FAM2 reporter strain and measuring luciferease activity.

Mentions: To find out whether the inhibitory effect of high MSX concentrations is a global effect on gene expression, the same type of experiment with 0.2 µM up to 500 µM MSX was performed using reporter strain FAM2, which has a truncated glnB promoter fused to luxAB (Figure 3). This truncated glnB promoter is devoid of the constitutive σ70 binding site and specifically monitors NtcA-dependent gene expression [37].


Nitrogen Starvation Acclimation in Synechococcus elongatus: Redox-Control and the Role of Nitrate Reduction as an Electron Sink.

Klotz A, Reinhold E, Doello S, Forchhammer K - Life (Basel) (2015)

Expression of the glnB::luxAB reporter gene within 5 h after MSX addition at concentrations indicated using the FAM2 reporter strain and measuring luciferease activity.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390884&req=5

life-05-00888-f003: Expression of the glnB::luxAB reporter gene within 5 h after MSX addition at concentrations indicated using the FAM2 reporter strain and measuring luciferease activity.
Mentions: To find out whether the inhibitory effect of high MSX concentrations is a global effect on gene expression, the same type of experiment with 0.2 µM up to 500 µM MSX was performed using reporter strain FAM2, which has a truncated glnB promoter fused to luxAB (Figure 3). This truncated glnB promoter is devoid of the constitutive σ70 binding site and specifically monitors NtcA-dependent gene expression [37].

Bottom Line: This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation.This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors.It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction.

View Article: PubMed Central - PubMed

Affiliation: Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany. alexander.klotz@uni-tuebingen.de.

ABSTRACT
Nitrogen starvation acclimation in non-diazotrophic cyanobacteria is characterized by a process termed chlorosis, where the light harvesting pigments are degraded and the cells gradually tune down photosynthetic and metabolic activities. The chlorosis response is governed by a complex and poorly understood regulatory network, which converges at the expression of the nblA gene, the triggering factor for phycobiliprotein degradation. This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation. Inhibition of glutamine synthetase (GS) by a precise dosage of l-methionine-sulfoximine (MSX) mimics the metabolic situation of nitrogen starvation. Addition of nitrate to such MSX-inhibited cells eliminates the associated redox-stress by enabling electron flow towards nitrate/nitrite reduction and thereby, prevents the induction of nblA expression and the associated chlorosis response. This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors. It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction.

No MeSH data available.


Related in: MedlinePlus