The pknH gene restrictively expressed in heterocysts is required for diazotrophic growth in the cyanobacterium Anabaena sp. strain PCC 7120

The nitrogenase complex in the heterocysts of the filamentous freshwater cyanobacterium Anabaena sp. PCC 7120 fixes atmospheric nitrogen to allow diazotrophic growth. The heterocyst cell envelope protects the nitrogenase from oxygen and consists of a polysaccharide and a glycolipid layer that are formed by a complex process involving the recruitment of different proteins. Here we studied the function of the putative nucleoside-diphosphate-sugar epimerase HgdA, which along with HgdB and HgdC is essential for deposition of the glycolipid layer and growth without a combined nitrogen source. Using site-directed mutagenesis and single homologous recombination approach, we performed a thoroughly functional characterization of HgdA and confirmed that the glycolipid layer of the hgdA mutant heterocyst is aberrant as shown by transmission electron microscopy and chemical analysis. The hgdA gene was expressed during late stages of the heterocyst differentiation. GFP-tagged HgdA protein localized inside the heterocysts. The purified HgdA protein had UDP-galactose 4-epimerase activity in vitro. This enzyme could be responsible for synthesis of heterocyst-specific glycolipid precursors, which could be transported over the cell wall by the ABC transporter components HgdB/HgdC.

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NrrA directly regulates expression of the fraF gene and antisense RNAs for fraE in the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120

Microbiology ◽

10.1099/mic.0.076703-0 ◽

2014 ◽

Vol 160 (5) ◽

pp. 844-850 ◽

Cited By ~ 5

Author(s):

Shigeki Ehira ◽

Masayuki Ohmori

Keyword(s):

Response Regulator ◽

Repeat Sequence ◽

Nitrogen Deprivation ◽

Antisense Rnas ◽

Regulated Expression ◽

Cyanobacterium Anabaena ◽

Anabaena Sp ◽

Dna Strand ◽

Pcc 7120 ◽

Diazotrophic Growth

The heterocystous cyanobacterium Anabaena sp. strain PCC 7120 grows as linear multicellular filaments that can contain hundreds of cells. Heterocysts, which are specialized cells for nitrogen fixation, are regularly intercalated among photosynthetic vegetative cells, and these cells are metabolically dependent on each other. Thus, multicellularity is essential for diazotrophic growth of heterocystous cyanobacteria. In Anabaena sp. strain PCC 7120, the fraF gene, which is required to limit filament length, is induced by nitrogen deprivation. The fraF transcripts extend to the fraE gene, which lies on the opposite DNA strand and could possess dual functionality, mRNAs for fraF and antisense RNAs for fraE. In the present study, we found that NrrA, a nitrogen-regulated response regulator, directly regulated expression of fraF. Induction of fraF by nitrogen deprivation was abolished by the nrrA disruption. NrrA specifically bound to the promoter region of fraF, and recognized an inverted repeat sequence. Thus, it is concluded that NrrA controls expression of mRNAs for fraF and antisense RNAs for fraE in response to nitrogen deprivation.

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Expanding the Natural Products Heterologous Expression Repertoire in the Model Cyanobacterium Anabaena sp. Strain PCC 7120: Production of Pendolmycin and Teleocidin B-4

10.26434/chemrxiv.11316098.v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

Patrick Videau ◽

Kaitlyn Wells ◽

Arun Singh ◽

Jessie Eiting ◽

Philip Proteau ◽

...

Keyword(s):

Natural Products ◽

Genome Mining ◽

Gene Clusters ◽

Combinatorial Biosynthesis ◽

Test Case ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Cyanobacterium Anabaena ◽

Anabaena Sp ◽

Pcc 7120

Cyanobacteria are prolific producers of natural products and genome mining has shown that many orphan biosynthetic gene clusters can be found in sequenced cyanobacterial genomes. New tools and methodologies are required to investigate these biosynthetic gene clusters and here we present the use of <i>Anabaena </i>sp. strain PCC 7120 as a host for combinatorial biosynthesis of natural products using the indolactam natural products (lyngbyatoxin A, pendolmycin, and teleocidin B-4) as a test case. We were able to successfully produce all three compounds using codon optimized genes from Actinobacteria. We also introduce a new plasmid backbone based on the native <i>Anabaena</i>7120 plasmid pCC7120ζ and show that production of teleocidin B-4 can be accomplished using a two-plasmid system, which can be introduced by co-conjugation.

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