An RpaA-Dependent Sigma Factor Cascade Sets the Timing of Circadian Transcriptional Rhythms in Synechococcus elongatus

Fleming, Kathleen; O’Shea, Erin K.

doi:10.1016/j.celrep.2018.11.049

Cited by 20 publications

(13 citation statements)

References 40 publications

(54 reference statements)

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“…However, comEA expression decreased in the dark after dusk, whereas it increased in the dark before dusk 37 , suggesting that comEA dark induction is tightly controlled by the clock. Notably, dprA induction did not occur in the absence of SigF2, consistent with evidence for sigF2dependent expression of dprA in a recent transcriptomics dataset obtained in LL 25 . constitutive promoter restored dprA dark induction and resulted in overexpression of dprA.…”

Section: Resultssupporting

confidence: 88%

“…To regulate circadian processes, an output pathway relays KaiC phosphorylation states to a two-component system with two antagonistic histidine kinases, CikA and SasA, and the response regulator RpaA 23 . RpaA serves as a master transcription factor that binds more than 134 transcript targets 24 and enables complex circadian gene expression patterns by regulating a cascade of interdependent sigma factors 25 .…”

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confidence: 99%

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The circadian clock and darkness control natural competence in cyanobacteria

et al. 2020

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The cyanobacterium Synechococcus elongatus is a model organism for the study of circadian rhythms. It is naturally competent for transformation-that is, it takes up DNA from the environment, but the underlying mechanisms are unclear. Here, we use a genome-wide screen to identify genes required for natural transformation in S. elongatus, including genes encoding a conserved Type IV pilus, genes known to be associated with competence in other bacteria, and others. Pilus biogenesis occurs daily in the morning, while natural transformation is maximal when the onset of darkness coincides with the dusk circadian peak. Thus, the competence state in cyanobacteria is regulated by the circadian clock and can adapt to seasonal changes of day length.

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Section: Resultssupporting

confidence: 88%

mentioning

confidence: 99%

The circadian clock and darkness control natural competence in cyanobacteria

et al. 2020

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“…However, comEA expression decreased in the dark after dusk, whereas it increased in the dark before dusk 29 , suggesting that comEA dark induction is tightly controlled by the clock. Notably, dprA induction did not occur in the absence of SigF2, consistent with evidence for sigF2 -dependent expression of dprA in a recent transcriptomics dataset obtained in LL 20 . The complementation of sigF2 from a constitutive promoter restored dprA dark induction and resulted in overexpression of dprA.…”

Section: Dusk and Darksupporting

confidence: 88%

“…To regulate circadian processes, an output pathway relays KaiC phosphorylation states to a two-component system with 2 antagonistic histidine kinases, CikA and SasA, and the response regulator RpaA 18 . RpaA serves as a master transcription factor that binds more than 134 transcript targets 19 and enables complex circadian gene expression patterns by regulating a cascade of interdependent sigma factors 20 .…”

mentioning

confidence: 99%

The circadian clock and darkness control natural competence in cyanobacteria

Taton

Erikson

Yang

et al. 2019

Preprint

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Natural genetic competence-based transformation contributed to the evolution of prokaryotes, including the cyanobacterial phylum that established oxygenic photosynthesis. The cyanobacterium Synechococcus elongatus is noted both as a model system for analyzing a prokaryotic circadian clock and for its facile, but poorly understood, natural competence. Here a genome-wide screen aimed at determining the genetic basis of competence in cyanobacteria identified all genes required for natural transformation in S. elongatus, including conserved Type IV pilus, competence-associated, and newly described genes, and revealed that the circadian clock controls the process. The findings uncover a daily program that determines the state of competence in S. elongatus and adapts to seasonal changes of day-length. Pilus biogenesis occurs daily in the morning, but competence is maximal upon the coincidence of circadian dusk and the onset of darkness. As in heterotrophic bacteria, where natural competence is conditionally regulated by nutritional or other stress, cyanobacterial competence is conditional and is tied to the daily cycle set by the cell’s most critical nutritional source, the Sun.

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“…Although S. elongatus is of great scientific interest in the context of direct bioconversion of carbon dioxide into fuels and plastic precursors (Atsumi et al ., 2009; Carbonell et al ., 2019), metabolic engineering to enhance production of fatty acids (Santos‐Merino et al ., 2018), circadian rhythm biology (Fleming and O'Shea, 2018) and many additional applications, its interaction with mammalian immunological processes has not previously been detailed. This study comprehensively assessed the safety of intravenous administration of S. elongatus cyanobacteria in rats in vivo to inform future exploration of this organism's utility in symbiotic therapeutics.…”

Section: Discussionmentioning

confidence: 99%

Safety of photosynthetic Synechococcus elongatus for in vivo cyanobacteria–mammalian symbiotic therapeutics

Williams

Wang

Paulsen

et al. 2020

Microbial Biotechnology

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The cyanobacterium Synechococcus elongatus (SE) has been shown to rescue ischaemic heart muscle after myocardial infarction by photosynthetic oxygen production. Here, we investigated SE toxicity and hypothesized that systemic SE exposure does not elicit a significant immune response in rats. Wistar rats intravenously received SE (n = 12), sterile saline (n = 12) or E. coli lipopolysaccharide (LPS, n = 4), and a subset (8 SE, 8 saline) received a repeat injection 4 weeks later. At baseline, 4 h, 24 h, 48 h, 8 days and 4 weeks after injection, clinical assessments, blood cultures, blood counts, lymphocyte phenotypes, liver function tests, proinflammatory cytokines and immunoglobulins were assessed. Across all metrics, SE rats responded comparably to saline controls, displaying no clinically significant immune response. As expected, LPS rats exhibited severe immunological responses. Systemic SE administration does not induce sepsis or toxicity in rats, thereby supporting the safety of cyanobacteria-mammalian symbiotic therapeutics using this organism.

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An RpaA-Dependent Sigma Factor Cascade Sets the Timing of Circadian Transcriptional Rhythms in Synechococcus elongatus

Abstract: Highlights d RpaA and RpaA-dependent sigma factors are required for circadian gene expression d RpaA-dependent sigma factors constitute an interdependent sigma factor cascade

Cited by 20 publications

References 40 publications

The circadian clock and darkness control natural competence in cyanobacteria

The circadian clock and darkness control natural competence in cyanobacteria

The circadian clock and darkness control natural competence in cyanobacteria

Safety of photosynthetic Synechococcus elongatus for in vivo cyanobacteria–mammalian symbiotic therapeutics

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