Transcriptional regulators ChlR and CnfR are essential for diazotrophic growth in nonheterocystous cyanobacteria

Tsujimoto, Ryoma; Kamiya, Narumi; Fujita, Yuichi

doi:10.1073/pnas.1323570111

Cited by 50 publications

(86 citation statements)

References 37 publications

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“…Interestingly, both P. serta PCC 8927 and P. tepida PCC 9214 nif clusters were flanked by the fdxB gene and a gene encoding a XRE (Xenobiotique response element) family transcriptional regulator. This regulator, named PatB in heterocystous cyanobacteria and CnfR in other diazotrophic cyanobacteria, was identified as the master regulator for the nif genes24. Moreover, three molybdenum transporter genes ( modIII, modA , and modB ) also flanked the nif gene cluster of P. tepida PCC 9214, as the one of Synechococcus sp.…”

Section: Resultsmentioning

confidence: 99%

Insights into the Planktothrix genus: Genomic and metabolic comparison of benthic and planktic strains

Pancrace

Barny

Ueoka

et al. 2017

Sci Rep

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Planktothrix is a dominant cyanobacterial genus forming toxic blooms in temperate freshwater ecosystems. We sequenced the genome of planktic and non planktic Planktothrix strains to better represent this genus diversity and life style at the genomic level. Benthic and biphasic strains are rooting the Planktothrix phylogenetic tree and widely expand the pangenome of this genus. We further investigated in silico the genetic potential dedicated to gas vesicles production, nitrogen fixation as well as natural product synthesis and conducted complementary experimental tests by cell culture, microscopy and mass spectrometry. Significant differences for the investigated features could be evidenced between strains of different life styles. The benthic Planktothrix strains showed unexpected characteristics such as buoyancy, nitrogen fixation capacity and unique natural product features. In comparison with Microcystis, another dominant toxic bloom-forming genus in freshwater ecosystem, different evolutionary strategies were highlighted notably as Planktothrix exhibits an overall greater genetic diversity but a smaller genomic plasticity than Microcystis. Our results are shedding light on Planktothrix evolution, phylogeny and physiology in the frame of their diverse life styles.

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Section: Resultsmentioning

confidence: 99%

Insights into the Planktothrix genus: Genomic and metabolic comparison of benthic and planktic strains

Pancrace

Barny

Ueoka

et al. 2017

Sci Rep

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“…Transcription of nifB, the first gene in the large cluster of genes that is responsible for the synthesis of nitrogenase, requires an activator protein, CnfR (originally called PatB) (26)(27)(28)(29), and also depends on highly conserved sequences upstream of the nifB transcription start site (25). An interaction between CnfR and these conserved nifB sequences has been implicated in the nonheterocystous cyanobacterium Leptolyngbya boryana (25), and direct binding of CnfR to the conserved sequences upstream of nifB was shown for CnfR from the unicellular nitrogen-fixing strain Cyanothece sp.…”

Section: Discussionmentioning

confidence: 99%

Role of the nifB1 and nifB2 Promoters in Cell-Type-Specific Expression of Two Mo Nitrogenases in the Cyanobacterium Anabaena variabilis ATCC 29413

2017

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Anabaena variabilis ATCC 29413 has one Mo nitrogenase that is made under oxic growth conditions in specialized cells called heterocysts and a second Mo nitrogenase that is made only under anoxic conditions in vegetative cells. The two large nif gene clusters responsible for these two nitrogenases are under the control of the promoter of the first gene in the operon, nifB1 or nifB2. Despite differences in the expression patterns of nifB1 and nifB2, related to oxygen and cell type, the regions upstream of their transcription start sites (tss) show striking homology, including three highly conserved sequences (CS). CS1, CS2, and the region just upstream from the tss were required for optimal expression from the nifB1 promoter, but CS3 and the 5= untranslated region (UTR) were not. Hybrid fusions of the nifB1 and nifB2 upstream regions revealed that the region including CS1, CS2, and CS3 of nifB2 could substitute for the similar region of nifB1; however, the converse was not true. Expression from the nifB2 promoter region required the CS1, CS2, and CS3 regions of nifB2 and also required the nifB2 5= UTR. A hybrid promoter that was mostly nifB2 but that had the region from about position Ϫ40 to the tss of nifB1 was expressed in heterocysts and in anoxic vegetative cells. Thus, addition of the nifB1 promoter region (from about position Ϫ40 to the tss of nifB1) in the nifB hybrid promoter supported expression in heterocysts but did not prevent the mostly nifB2 promoter from also functioning in anoxic vegetative cells. IMPORTANCE In the filamentous cyanobacterium Anabaena variabilis, two Mo nitrogenase gene clusters, nif1 and nif2, function under different environmental conditions in different cell types. Little is known about the regulation of transcription from the promoter upstream of the first gene of the cluster, which drives transcription of each of these two large operons. The similarity in the sequences upstream of the primary promoters for the two nif gene clusters belies the differences in their expression patterns. Analysis of these nif promoters in strains with mutations in the conserved sequences and in strains with hybrid promoters, comprising parts from nif1 and nif2, provides strong evidence that each promoter has key elements required for cell-type-specific expression of the nif1 and nif2 gene clusters.KEYWORDS Anabaena, cyanobacteria, heterocysts, nitrogenase, regulation, transcriptional regulation F ilamentous heterocystous cyanobacteria fix atmospheric nitrogen under oxic growth conditions in specialized cells called heterocysts that differentiate in a semiregular pattern in a filament. They comprise about 5 to 10% of the cells in filaments in cultures grown in an environment that is deficient in fixed nitrogen (1-5). Heterocysts are microoxic; they have a glycolipid layer that restricts oxygen diffusion into the cell, lack components of oxygen-evolving photosystem II, and have high levels of respiration, which together protect the oxygen-labile nitrogenase from oxygen (6-10).

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“…However, some nitrogen-fixing cyanobacteria, such as Leptolyngbya boryana and Nostoc PCC 7120, do not have ChlE. In these species, the activity of the low-oxygen type isoform ChlA II is high enough for Chl biosynthesis under nitrogen-fixing conditions [25].…”

Section: Evolution Of Chle/bchementioning

confidence: 99%

Identification of the chlE gene encoding oxygen-independent Mg-protoporphyrin IX monomethyl ester cyclase in cyanobacteria

Yamanashi

Minamizaki

Fujita

2015

Biochemical and Biophysical Research Communications

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The fifth ring (E-ring) of chlorophyll (Chl) a is produced by Mg-protoporphyrin IX monomethyl ester (MPE) cyclase. There are two evolutionarily unrelated MPE cyclases: oxygen-independent (BchE) and oxygen-dependent (ChlA/AcsF) MPE cyclases. Although ChlA is the sole MPE cyclase in Synechocystis PCC 6803, it is yet unclear whether BchE exists in cyanobacteria. A BLAST search suggests that only few cyanobacteria possess bchE. Here, we report that two bchE candidate genes from Cyanothece strains PCC 7425 and PCC 7822 restore the photosynthetic growth and bacteriochlorophyll production in a bchE-lacking mutant of Rhodobacter capsulatus. We termed these cyanobacterial bchE orthologs "chlE."

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Transcriptional regulators ChlR and CnfR are essential for diazotrophic growth in nonheterocystous cyanobacteria

Cited by 50 publications

References 37 publications

Insights into the Planktothrix genus: Genomic and metabolic comparison of benthic and planktic strains

Insights into the Planktothrix genus: Genomic and metabolic comparison of benthic and planktic strains

Role of the nifB1 and nifB2 Promoters in Cell-Type-Specific Expression of Two Mo Nitrogenases in the Cyanobacterium Anabaena variabilis ATCC 29413

Identification of the chlE gene encoding oxygen-independent Mg-protoporphyrin IX monomethyl ester cyclase in cyanobacteria

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