Different recombination site specificity of two developmentally regulated genome rearrangements

Golden, James W.; Mulligan, Martin E.; Haselkorn, Robert

doi:10.1038/327526a0

Cited by 114 publications

(63 citation statements)

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“…The HindIlI fragment An256, which spans one of the nipD element recombination sites (20), hybridized with a 2.9-kb band in wild-type vegetative cell DNA and with 2.1-and 1.8-kb bands in heterocyst DNA. The EcoRI fragment An155, which spans one of the fdxN element recombination sites (19), hybridized with a 3.6-kb band in wild-type vegetative cell DNA and with 4.6-and 2.2-kb bands in heterocyst DNA. AMC236 did not rearrange the niJD element or fdxN element under any of these growth conditions.…”

Section: Methodsmentioning

confidence: 99%

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

1994

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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, rbcL, and nifH. We have constructed a ntcA null mutant by interrupting the gene with an omega Spr-Smr cassette. The ntcA mutant was not able to grow with nitrate or atmospheric dinitrogen as the sole nitrogen source but could be grown on medium containing ammonium. The ntcA mutant was unable to form heterocysts and did not rearrange the nifD or fdxN elements after induction on a medium lacking combined nitrogen. Northern (RNA) analysis of ntcA in the wild-type strain during nitrogen stepdown showed a peak of ntcA message at an early stage (12 h) of heterocyst induction. Complementation of the ntcA mutant with a DNA fragment containing the ntcA gene and 251 bp of upstream sequence on a shuttle vector restored a wild-type phenotype; however, a similar construction containing 87 bp of upstream sequence only partially restored the phenotype. Northern analysis of RNA samples isolated from ammonium-grown cultures of the ntcA mutant showed reduced amounts of glnA message and the absence of a 1.7-kb transcript. In the wild type, the 1.7-kb transcript represents the majority of glnA transcripts after nitrogen stepdown. The ntcA mutant showed a normal pattern of rbcLS messages under these growth conditions.

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Section: Methodsmentioning

confidence: 99%

“…The blot containing HindIII-digested DNA was probed with the HindlIl fragment An256 (21), which contains the niffl-proximal recombination site of the nifD element. The same blot was stripped and then probed with the EcoRI fragment An155 (19), which contains the nifB-proximal recombination site of the fdxN element.…”

Section: Methodsmentioning

confidence: 99%

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

1994

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“…A Northern blot of total RNA (10 \Lg per lane) from Anabaena 7120 isolated at 6-hr intervals from an N~ induced culture as described (Golden et al 1987) was obtained from Bianca Brahamsha. Northern blot analysis was performed as described (Maniatis et al 1982).…”

Section: Genes and Developmentmentioning

confidence: 99%

Characterization of a gene controlling heterocyst differentiation in the cyanobacterium Anabaena 7120.

Buikema¹,

Haselkorn²

1991

Genes Dev.

304

360

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Anabaena 7120 mutant 216 fails to differentiate heterocysts. We previously identified a 2.4-kb wild-type DNA fragment able to complement this mutant. We show here that the sequence of this fragment contains a single open reading frame [hetR), encoding a 299-amino-acid protein. Conjugation of deletion subclones of this fragment into strain 216 showed that the /ieti?-coding region is both necessary and sufficient for complementation of the Het~ phenotype. The mutation in 216 is located at nucleotide 535 in the betR gene, converting a serine at position 179 in the wild-type protein to an asparagine in the mutant. Interruption of the hetR gene in wild-type cells results in a mutant phenotype identical to that of 216. Both 216 and wild-type cells containing wild-type hetR on a plasmid display increased frequency of heterocysts, even on media containing fixed nitrogen. These results suggest that hetR encodes a product that is not only essential for but also controls heterocyst development. This putative regulatory protein lacks known structural motifs characteristic of transcription factors and probably acts at a level one or more steps removed from its target genes.

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“…nifJ is not part of the cluster (4). The nifB-fdxNnifS-nifU operon is interrupted by a 55-kb insertion in fdxN, and the nifD gene has an 11-kb insertion, both of which are excised during heterocyst differentiation (19,20). The heterocyst ferredoxin gene of Anabaena sp.…”

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confidence: 99%

Characterization of nifB, nifS, and nifU genes in the cyanobacterium Anabaena variabilis: NifB is required for the vanadium-dependent nitrogenase

Lyons

Thiel

1995

J Bacteriol

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Anabaena variabilis ATCC 29413 is a heterotrophic, nitrogen-fixing cyanobacterium containing both a Mo-dependent nitrogenase encoded by the nif genes and V-dependent nitrogenase encoded by the vnf genes. The nifB, nifS, and nifU genes of A. variabilis were cloned, mapped, and partially sequenced. The fdxN gene was between nifB and nifS. Growth and acetylene reduction assays using wild-type and mutant strains indicated that the nifB product (NifB) was required for nitrogen fixation not only by the enzyme encoded by the nif genes but also by the enzyme encoded by the vnf genes. Neither NifS nor NifU was essential for nitrogen fixation in A. variabilis.Anabaena spp. are filamentous cyanobacteria capable of fixing dinitrogen in specialized morphologically distinct cells called heterocysts (18,41). Under diazotrophic growth conditions, vegetative cells compose 90 to 95% of the cells in a filament and contain both photosystems I and II. The other 5 to 10% of cells are heterocysts that have only photosystem I and therefore evolve no oxygen (40). Additional envelope layers in heterocysts may protect nitrogenase from oxygen (38, 39).Many nif genes have been identified in Anabaena sp. strain PCC 7120: one large cluster contains nifB, fdxN, nifS, nifU, nifH, nifD, nifK, nifN, nifX, open reading frame 3, nifW, open reading frame 1, open reading frame 2, and fdxH (8,23,30,33,36,37,42). nifJ is not part of the cluster (4). The nifB-fdxNnifS-nifU operon is interrupted by a 55-kb insertion in fdxN, and the nifD gene has an 11-kb insertion, both of which are excised during heterocyst differentiation (19,20). The heterocyst ferredoxin gene of Anabaena sp. strain PCC 7120, fdxH, is downstream of the other characterized nif genes in the cluster (8). The nif genes of A. variabilis ATCC 29413 that are the homologs of the nif genes of Anabaena sp. strain PCC 7120 have been cloned and mapped (24), and the 11-kb excision element, but not the 55-kb excision element, has been found in that nif cluster (9).Besides the nif genes that encode nitrogenase 1, which requires a Mo cofactor, Anabaena variabilis also contains vnf genes that encode nitrogenase 2, which requires a V cofactor (53). Nitrogenases that do not require Mo were first described in Azotobacter vinelandii, which has nitrogenase 1, nitrogenase 2, and nitrogenase 3. Nitrogenase 3, which requires only Fe in the cofactor, is encoded by the anf genes (6, 10, 27). The vnf and anf systems of A. vinelandii do not have homologs of all the genes of the nif system. Known vnf and anf genes include vnfDGK, homologous to nifDK; vnfEN, homologous to nifEN; vnfA, homologous to nifA; and anfHDGK, homologous to nif HDK (6). The nifB, nifS, nifU, nifM, and nifV genes are required for the activity of all three nitrogenases of A. vinelandii (28,29). The vnfEN genes may also function in the anf system (6). The vnf-and anf-encoded nitrogenases are repressed by Mo and have the ability to reduce acetylene not only to ethylene but also to ethane, which is one criterion for the presence of these altern...

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Different recombination site specificity of two developmentally regulated genome rearrangements

Cited by 114 publications

References 1 publication

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

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

Characterization of a gene controlling heterocyst differentiation in the cyanobacterium Anabaena 7120.

Characterization of nifB, nifS, and nifU genes in the cyanobacterium Anabaena variabilis: NifB is required for the vanadium-dependent nitrogenase

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