Constitutive and nitrogen‐regulated promoters of the petH gene encoding ferredoxin:NADP+ reductase in the heterocyst‐forming cyanobacterium Anabaena sp

Valladares, Ana; Muro‐Pastor, Alicia M.; Fillat, Marı́a F.; Herrero, Antonia; Flores, Enrique

doi:10.1016/s0014-5793(99)00404-4

Cited by 57 publications

(59 citation statements)

References 33 publications

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“…The regulation of the Anabaena PCC 7120 nifHDK operon has been studied for over 25 years (14,18,20,43,44,50,53); however, little is known about the transcription components that regulate this operon. Our results suggest that sigE is in -FIG.…”

Section: Discussionmentioning

confidence: 99%

The sigE Gene Is Required for Normal Expression of Heterocyst-Specific Genes in Anabaena sp. Strain PCC 7120

et al. 2011

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The filamentous cyanobacterium Anabaena (Nostoc) sp. strain PCC 7120 produces specialized cells for nitrogen fixation called heterocysts. Previous work showed that the group 2 sigma factor sigE (alr4249; previously called sigF) is upregulated in differentiating heterocysts 16 h after nitrogen step-down. We now show that the sigE gene is required for normal heterocyst development and normal expression levels of several heterocyst-specific genes. Mobility shift assays showed that the transcription factor NtcA binds to sites in the upstream region of sigE and that this binding is enhanced by 2-oxoglutarate (2-OG). Deletions of the region containing the NtcA binding sites in P sigE -gfp reporter plasmids showed that the sites contribute to normal developmental regulation but are not essential for upregulation in heterocysts. Northern RNA blot analysis of nifH mRNA revealed delayed and reduced transcript levels during heterocyst differentiation in a sigE mutant background. Quantitative reverse transcription-PCR (qRT-PCR) analyses of the sigE mutant showed lower levels of transcripts for nifH, fdxH, and hglE2 but normal levels for hupL. We developed a P nifHD -gfp reporter construct that showed strong heterocyst-specific expression. Time-lapse microscopy of the P nifHD -gfp reporter in a sigE mutant background showed delayed development and undetectable green fluorescent protein (GFP) fluorescence. Overexpression of sigE caused accelerated heterocyst development, an increased heterocyst frequency, and premature expression of GFP fluorescence from the P nifHD -gfp reporter.

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Section: Discussionmentioning

confidence: 99%

The sigE Gene Is Required for Normal Expression of Heterocyst-Specific Genes in Anabaena sp. Strain PCC 7120

et al. 2011

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“…petH produces two mRNAs; one is constitutive (starts at nucleotide Ϫ63 from Met-1) and the other one is used in the absence of combined nitrogen (starts at nucleotide Ϫ188 from Met-1) (30). This larger transcript is expected to produce FNR S by a yet-unknown posttranscriptional mechanism that would prevent initiation at Met-1.…”

Section: Discussionmentioning

confidence: 99%

A second isoform of the ferredoxin:NADP oxidoreductase generated by an in-frame initiation of translation

Thomas

Ughy

Lagoutte

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

100

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Ferredoxin:NADP oxidoreductases (FNRs) constitute a family of flavoenzymes that catalyze the exchange of reducing equivalents between one-electron carriers and the two-electron-carrying NADP(H). The main role of FNRs in cyanobacteria and leaf plastids is to provide the NADPH for photoautotrophic metabolism. In root plastids, a distinct FNR isoform is found that has been postulated to function in the opposite direction, providing electrons for nitrogen assimilation at the expense of NADPH generated by heterotrophic metabolism. A multiple gene family encodes FNR isoenzymes in plants, whereas there is only one FNR gene (petH) in cyanobacteria. Nevertheless, we detected two FNR isoforms in the cyanobacterium Synechocystis sp. strain PCC6803. One of them (FNR S Ϸ34 kDa) is similar in size to the plastid FNR and specifically accumulates under heterotrophic conditions, whereas the other one (FNRL Ϸ46 kDa) contains an extra N-terminal domain that allows its association with the phycobilisome. Site-directed mutants allowed us to conclude that the smaller isoform, FNR S, is produced from an internal ribosome entry site within the petH ORF. Thus we have uncovered a mechanism by which two isoforms are produced from a single gene, which is, to our knowledge, novel in photosynthetic bacteria. Our results strongly suggest that FNRL is an NADP ؉ reductase, whereas FNRS is an NADPH oxidase.

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“…PCC 6803 icd gene, coding for the isocytrate dehydrogenase (Muro-Pastor et al, 1996); the Anabaena sp. PCC 7120 rbcL gene encoding for the large subunit of Rubisco (Ramasubramaniam et al, 1994); and the gor gene, coding the antioxidant defense enzyme glutathione reductase (Jiang et al, 1997) or the petH gene coding for the ferredoxin NADPϩ-reductase (Valladares et al, 1999). Some of the NtcA up-regulated genes (like glnA or glnB) have been shown to be under electron transport control in Synechocystis sp.…”

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confidence: 99%

Redox Control of ntcA Gene Expression in Synechocystis sp. PCC 6803. Nitrogen Availability and Electron Transport Regulate the Levels of the NtcA Protein

Alfonso

Perewoska

Kirilovsky³

2001

Plant Physiology

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In this work we have studied the influence of the cellular redox status in the expression of the Synechocystis sp. PCC 6803 ntcA gene. Two different ntcAtranscripts with different 5′ ends were detected, depending on the different dark/light or nitrogen availability conditions. Accumulation of a 0.8-kb ntcA message was light and nitrogen dependent, whereas a longer 1.2-kb ntcA transcript was neither light nor nitrogen regulated. NtcA protein levels increased concomitantly with the accumulation of the 0.8-kb ntcAtranscript. The light-dependent accumulation of the ntcAgene and the NtcA protein was sensitive to electron transport inhibitors. In addition, Glc-grown Synechocystis sp. cells showed a similar ntcA expression pattern in darkness to that observed under illumination. These data suggested that electron transport, and not light per se may regulatentcA gene expression. Primer extension analysis, together with gel mobility-shift assays, demonstrated that in vitro, the Synechocystis sp. NtcA protein specifically bound to the putative promoter region from the light/nitrogen-dependentntcA transcript but not to that from the constitutive 1.2-kb ntcA mRNA. Band-shift experiments carried out in the presence of thiol oxidizing/modifiying agents and different reducing/oxidizing conditions suggested that NtcA binding to its own promoter was under a thiol-dependent redox mechanism. Our results suggest that the cellular redox status plays a central role in the autoregulatory mechanism of the NtcA protein.

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Constitutive and nitrogen‐regulated promoters of the petH gene encoding ferredoxin:NADP⁺ reductase in the heterocyst‐forming cyanobacterium Anabaena sp

Cited by 57 publications

References 33 publications

The sigE Gene Is Required for Normal Expression of Heterocyst-Specific Genes in Anabaena sp. Strain PCC 7120

The sigE Gene Is Required for Normal Expression of Heterocyst-Specific Genes in Anabaena sp. Strain PCC 7120

A second isoform of the ferredoxin:NADP oxidoreductase generated by an in-frame initiation of translation

Redox Control of ntcA Gene Expression in Synechocystis sp. PCC 6803. Nitrogen Availability and Electron Transport Regulate the Levels of the NtcA Protein

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