Clustered Genes Required for the Synthesis of Heterocyst Envelope Polysaccharide in
            <i>Anabaena</i>
            sp. Strain PCC 7120

Huang, Guo N.; Fan, Qing; Lechno‐Yossef, Sigal; Wojciuch, Elizabeth; Wölk, C. Peter; Kaneko, Takakazu; Tabata, Satoshi

doi:10.1128/jb.187.3.1114-1123.2005

Cited by 76 publications

(89 citation statements)

References 46 publications

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“…as the template, and cloned into plasmid pGEM-T Easy (Promega Corp.). Insertion of a PstI-cat-erm-oriT(RK2)-PstI cassette from pRL2665b (12) into the unique PstI site of the resulting plasmid yielded plasmid pRL2787a. pRL2787a was transferred to Anabaena sp.…”

Section: Methodsmentioning

confidence: 99%

Septum-Localized Protein Required for Filament Integrity and Diazotrophy in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

et al. 2007

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Heterocysts, formed when filamentous cyanobacteria, such as Anabaena sp. strain PCC 7120, are grown in the absence of combined nitrogen, are cells that are specialized in fixing atmospheric nitrogen (N 2 ) under oxic conditions and that transfer fixed nitrogen to the vegetative cells of the filament. Anabaena sp. mutants whose sepJ gene (open reading frame alr2338 of the Anabaena sp. genome) was affected showed filament fragmentation and arrested heterocyst differentiation at an early stage. In a sepJ insertional mutant, a layer similar to a heterocyst polysaccharide layer was formed, but the heterocyst-specific glycolipids were not synthesized. The sepJ mutant did not exhibit nitrogenase activity even when assayed under anoxic conditions. In contrast to proheterocysts produced in the wild type, those produced in the sepJ mutant still divided. SepJ is a multidomain protein whose N-terminal region is predicted to be periplasmic and whose C-terminal domain resembles an export permease. Using a green fluorescent protein translationally fused to the carboxyl terminus of SepJ, we observed that in mature heterocysts and vegetative cells, the protein is localized at the intercellular septa, and when cell division starts, it is localized in a ring whose position is similar to that of a Z ring. SepJ is a novel composite protein needed for filament integrity, proper heterocyst development, and diazotrophic growth.

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Section: Methodsmentioning

confidence: 99%

Septum-Localized Protein Required for Filament Integrity and Diazotrophy in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

et al. 2007

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“…strain PCC 7120 and the transposon mutant derivatives FQ671 (hepN), FQ1487 (hepS), FQ1227 (henR; complemented by plasmid pRL3194, which also complemented henR mutant FQ621 [17]), and Y7 (hepK) (74) were used in this study. PCC 7120 was maintained in AA/8 liquid medium as described previously (33); wild-type cultures to be used as inocula for experiments were supplemented with nitrate. Mutant cultures were supplemented with nitrate plus 20 g/ml neomycin sulfate.…”

Section: Methodsmentioning

confidence: 99%

“…Proheterocysts deposit a protective, enveloping layer of polysaccharide (Hep). Deposition depends upon a cluster of genes (33), hepA among them (32,64,74), whose expression is up-regulated 8 h after nitrogen step-down (14). Mutations in other genes, e.g., hepB (alr3698), alr3699, and all4160 (46, 64; Q.…”

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Mutations in Four Regulatory Genes Have Interrelated Effects on Heterocyst Maturation in Anabaena sp. Strain PCC 7120

Lechno‐Yossef¹,

Fan²,

Ehira

et al. 2006

J Bacteriol

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Regulatory genes hepK, hepN, henR, and hepS are required for heterocyst maturation in Anabaena sp. strain PCC 7120. They presumptively encode two histidine kinases, a response regulator, and a serine/threonine kinase, respectively. To identify relationships between those genes, we compared global patterns of gene expression, at 14 h after nitrogen step-down, in corresponding mutants and in the wild-type strain. Heterocyst envelopes of mutants affected in any of those genes lack a homogeneous, polysaccharide layer. Those of a henR mutant also lack a glycolipid layer. patA, which encodes a positive effector of heterocyst differentiation, was up-regulated in all mutants except the hepK mutant, suggesting that patA expression may be inhibited by products related to heterocyst development. hepS and hepK were up-regulated if mutated and so appear to be negatively autoregulated. HepS and HenR regulated a common set of genes and so appear to belong to one regulatory system. Some nontranscriptional mechanism may account for the observation that henR mutants lack, and hepS mutants possess, a glycolipid layer, even though both mutations down-regulated genes involved in formation of the glycolipid layer. HepK and HepN also affected transcription of a common set of genes and therefore appear to share a regulatory pathway. However, the transcript abundance of other genes differed very significantly from expression in the wild-type strain in either the hepK or hepN mutant while differing very little from wild-type expression in the other of those two mutants. Therefore, hepK and hepN appear to participate also in separate pathways.

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“…Synthesis and deposition of the polysaccharide layer requires the expression of a cluster of genes that constitute the HEP island (23). The expression of these genes is upregulated during the early stages of heterocyst differentiation.…”

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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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Clustered Genes Required for the Synthesis of Heterocyst Envelope Polysaccharide in Anabaena sp. Strain PCC 7120

Cited by 76 publications

References 46 publications

Septum-Localized Protein Required for Filament Integrity and Diazotrophy in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

Septum-Localized Protein Required for Filament Integrity and Diazotrophy in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

Mutations in Four Regulatory Genes Have Interrelated Effects on Heterocyst Maturation in Anabaena sp. Strain PCC 7120

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

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