Transcriptional dynamics of developmental genes assessed with an FMN-dependent fluorophore in mature heterocysts of Anabaena sp. strain PCC 7120

Videau, Patrick; Oshiro, Reid T.; Cozy, Loralyn M.; Callahan, Sean M.

doi:10.1099/mic.0.078352-0

Cited by 11 publications

(10 citation statements)

References 39 publications

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“…As shown by a patS promoter fusion to gfp, transcription of patS initially increases in all cells of the filament but resolves to a pattern of about every tenth cell by 8 to 10 h after combined nitrogen removal (8 to 10 h NϪ) (20). This expression pattern is maintained until about 27 h NϪ, when transcription of patS is halted in mature heterocysts (39,51).…”

Section: Figmentioning

confidence: 92%

Mutation of the murC and murB Genes Impairs Heterocyst Differentiation in Anabaena sp. Strain PCC 7120

et al. 2016

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To stabilize cellular integrity in the face of environmental perturbations, most bacteria, including cyanobacteria, synthesize and maintain a strong, flexible, three-dimensional peptidoglycan lattice. Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium capable of differentiating morphologically distinct nitrogen-fixing heterocyst cells in a periodic pattern. While heterocyst development has been shown to require proper peptidoglycan remodeling, the role of peptidoglycan synthesis has remained unclear. Here we report the identification of two peptidoglycan synthesis genes, murC (alr5065) and murB (alr5066), as required for heterocyst development. The murC and murB genes are predicted to encode a UDP-N-acetylmuramate:L-alanine ligase and a UDP-N-acetylenolpyruvoylglucosamine reductase, respectively, and we confirm enzymatic function through complementation of Escherichia coli strains deficient for these enzymes. Cells depleted of either murC or murB expression failed to differentiate heterocysts under normally inducing conditions and displayed decreased filament integrity. To identify the stage(s) of development affected by murC or murB depletion, the spatial distribution of expression of the patterning marker gene, patS, was examined. Whereas murB depletion did not affect the pattern of patS expression, murC depletion led to aberrant expression of patS in all cells of the filament. Finally, expression of gfp controlled by the region of DNA immediately upstream of murC was enriched in differentiating cells and was repressed by the transcription factor NtcA. Collectively, the data in this work provide evidence for a direct link between peptidoglycan synthesis and the maintenance of a biological pattern in a multicellular organism. IMPORTANCEMulticellular organisms that differentiate specialized cells must regulate morphological changes such that both cellular integrity and the dissemination of developmental signals are preserved. Here we show that the multicellular bacterium Anabaena, which differentiates a periodic pattern of specialized heterocyst cells, requires peptidoglycan synthesis by the murine ligase genes murC (alr5065) and murB (alr5066) for maintenance of patterned gene expression, filament integrity, and overall development. This work highlights the significant influence that intracellular structure and intercellular connections can have on the execution of a developmental program. Bacteria have evolved diverse strategies to combat environmental changes, including osmotic pressure, oxidative damage, and nutrient deprivation (reviewed in references 1 and 2). To prevent lysis from such environmental stressors, two different cell wall architectures have been adopted that also serve as a basis for classification. Gram-positive bacteria have a characteristically thick peptidoglycan layer (20 to 80 nm) outside an inner membrane, while Gram-negative strains have an inner membrane and outer membrane separated by a thin peptidoglycan layer (1 to 7 nm). Cyanobacteria have a Gram-negative cell wa...

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Section: Figmentioning

confidence: 92%

Mutation of the murC and murB Genes Impairs Heterocyst Differentiation in Anabaena sp. Strain PCC 7120

et al. 2016

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“…A region containing hetN ‐YFP‐His6 was amplified by PCR using pPJAV440 as a template with the primers hetN‐EcoRI and pET28B‐BglII‐R. The product was cloned as an EcoRI–BglII fragment into the EcoRI–BamHI sites in pPJAV213 (Videau et al ., ) to create pPJAV437.…”

Section: Methodsmentioning

confidence: 99%

Mutation of sepJ reduces the intercellular signal range of a hetN‐dependent paracrine signal, but not of a patS‐dependent signal, in the filamentous cyanobacterium Anabaena sp. strain PCC 7120

Rivers

Videau

Callahan

2014

Molecular Microbiology

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“…HetN differs from PatS in two important respects. First, its expression starts at a late stage of differentiation and persists in mature heterocysts (as opposed to induction at an early stage and downregulation in mature heterocysts) (Callahan and Buikema, ; Videau et al ., ). Second, HetN is important in the maintenance of the pattern of heterocysts but not its initial formation (Callahan and Buikema, ).…”

Section: Introductionmentioning

confidence: 97%

Ancient association of cyanobacterial multicellularity with the regulator HetR and an RGSGR pentapeptide‐containing protein (PatX)

Elhai

Khudyakov

2018

Molecular Microbiology

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One simple model to explain biological pattern postulates the existence of a stationary regulator of differentiation that positively affects its own expression, coupled with a diffusible suppressor of differentiation that inhibits the regulator's expression. The first has been identified in the filamentous, heterocyst-forming cyanobacterium, Anabaena PCC 7120 as the transcriptional regulator, HetR and the second as the small protein, PatS, which contains a critical RGSGR motif that binds to HetR. HetR is present in almost all filamentous cyanobacteria, but only a subset of heterocyst-forming strains carry proteins similar to PatS. We identified a third protein, PatX that also carries the RGSGR motif and is coextensive with HetR. Amino acid sequences of PatX contain two conserved regions: the RGSGR motif and a hydrophobic N-terminus. Within 69 nt upstream from all instances of the gene is a DIF1 motif correlated in Anabaena with promoter induction in developing heterocysts, preceded in heterocyst-forming strains by an apparent NtcA-binding site, associated with regulation by nitrogen-status. Consistent with a role in the simple model, PatX is expressed dependent on HetR and acts to inhibit differentiation. The acquisition of the PatX/HetR pair preceded the appearance of both PatS and heterocysts, dating back to the beginnings of multicellularity.

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Transcriptional dynamics of developmental genes assessed with an FMN-dependent fluorophore in mature heterocysts of Anabaena sp. strain PCC 7120

Cited by 11 publications

References 39 publications

Mutation of the murC and murB Genes Impairs Heterocyst Differentiation in Anabaena sp. Strain PCC 7120

Mutation of the murC and murB Genes Impairs Heterocyst Differentiation in Anabaena sp. Strain PCC 7120

Mutation of sepJ reduces the intercellular signal range of a hetN‐dependent paracrine signal, but not of a patS‐dependent signal, in the filamentous cyanobacterium Anabaena sp. strain PCC 7120

Ancient association of cyanobacterial multicellularity with the regulator HetR and an RGSGR pentapeptide‐containing protein (PatX)

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