Cyanobacterial ycf27 gene products regulate energy transfer from phycobilisomes to photosystems I and II

Ashby, Michael

doi:10.1016/s0378-1097(99)00547-9

Cited by 30 publications

(54 citation statements)

References 13 publications

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“…strain PCC 6803. In that strain, rpaA-null mutants have an increased efficiency of energy transfer to PSII relative to PSI (22). Our pigment absorbance data collected at 0 h support the hypothesis that RpaA also affects photosynthetic parameters in S. elongatus (Fig.…”

Section: Synechocystissupporting

confidence: 84%

“…Although this study did not directly address changes in photosynthesis, a similar relative increase in chlorophyll was observed in Synechocystis sp. strain PCC 6803 ΔrpaA mutants (22). The broad differences in pigmentation at 0 h between WT and ΔrpaA (Fig.…”

Section: Darkness Initiates Pigmentation Changes and Rapid Cell Deathmentioning

confidence: 97%

“…RpaA was first identified in another cyanobacterium, Synechocystis sp. strain PCC 6803, as an OmpR-type response regulator that influences the ratio of light energy transfer from light-harvesting phycobilisomes to photosystem I (PSI) vs. PSII (22). Thus, it is not surprising that RpaA affects core energy-producing pathways when cells are exposed to light.…”

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confidence: 99%

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Redox crisis underlies conditional light–dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA

Diamond

Rubin

Shultzaberger

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Cyanobacteria evolved a robust circadian clock, which has a profound influence on fitness and metabolism under daily lightdark (LD) cycles. In the model cyanobacterium Synechococcus elongatus PCC 7942, a functional clock is not required for diurnal growth, but mutants defective for the response regulator that mediates transcriptional rhythms in the wild-type, regulator of phycobilisome association A (RpaA), cannot be cultured under LD conditions. We found that rpaA-null mutants are inviable after several hours in the dark and compared the metabolomes of wild-type and rpaA-null strains to identify the source of lethality. Here, we show that the wild-type metabolome is very stable throughout the night, and this stability is lost in the absence of RpaA. Additionally, an rpaA mutant accumulates excessive reactive oxygen species (ROS) during the day and is unable to clear it during the night. The rpaA-null metabolome indicates that these cells are reductant-starved in the dark, likely because enzymes of the primary nighttime NADPH-producing pathway are direct targets of RpaA. Because NADPH is required for processes that detoxify ROS, conditional LD lethality likely results from inability of the mutant to activate reductant-requiring pathways that detoxify ROS when photosynthesis is not active. We identified second-site mutations and growth conditions that suppress LD lethality in the mutant background that support these conclusions. These results provide a mechanistic explanation as to why rpaA-null mutants die in the dark, further connect the clock to metabolism under diurnal growth, and indicate that RpaA likely has important unidentified functions during the day.C yanobacteria are both key agents of global carbon and nitrogen cycles and promising platforms for renewable chemicals, fuels, and nutraceuticals (1-3). Understanding the control mechanisms that govern the flow of carbon and nitrogen through these organisms is crucial for predicting their behavior in natural environments as well as for improving engineering strategies. Although the basic pathways for carbon and nitrogen metabolism, and their regulation, are well understood in heterotrophic bacteria, cyanobacteria exhibit important deviations in these core metabolic pathways (4-7). Additionally, metabolic control mechanisms in cyanobacteria evolved to be compatible with photoautotrophic metabolism and the dramatic shifts that are imposed on those pathways by predictable daily light-dark (LD) cycles. Examples include enzymatic activity that responds to light-dependent cellular redox changes (8-11); the preference for NADPH, the reductant produced by the photochemical reactions, over NADH by many biosynthetic enzymes (12, 13); and a circadian clock that drives 24-h transcriptional rhythms in most genes (14-16).A daily LD cycle presents a strong metabolic driver for the photosynthetic cyanobacteria, but a circadian clock also imposes daily cycles in transcription and redox regulatory systems (17, 18). Circadian measurements historically have been performed in...

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Section: Synechocystissupporting

confidence: 84%

Section: Darkness Initiates Pigmentation Changes and Rapid Cell Deathmentioning

confidence: 97%

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Redox crisis underlies conditional light–dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA

Diamond

Rubin

Shultzaberger

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…strain PCC6803, two proteins that are involved in the regulation of transfer of excitation energy from the phycobilisome to PSI and PSII, respectively. For example, deletion of rpaA results in increased efficiency of energy transfer from phycobilisomes to PSII relative to PSI (8). Although seemingly involved in phycobilisome state transitions, these DNA-binding response regulators are, surprisingly, present in single copy in most marine picocyanobacteria.…”

Section: Two-component Systems and Crp-type Regulatorsmentioning

confidence: 99%

Ecological Genomics of Marine Picocyanobacteria

Scanlan

Ostrowski

Mazard

et al. 2009

Microbiol Mol Biol Rev

657

824

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SUMMARY Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus numerically dominate the picophytoplankton of the world ocean, making a key contribution to global primary production. Prochlorococcus was isolated around 20 years ago and is probably the most abundant photosynthetic organism on Earth. The genus comprises specific ecotypes which are phylogenetically distinct and differ markedly in their photophysiology, allowing growth over a broad range of light and nutrient conditions within the 45°N to 40°S latitudinal belt that they occupy. Synechococcus and Prochlorococcus are closely related, together forming a discrete picophytoplankton clade, but are distinguishable by their possession of dissimilar light-harvesting apparatuses and differences in cell size and elemental composition. Synechococcus strains have a ubiquitous oceanic distribution compared to that of Prochlorococcus strains and are characterized by phylogenetically discrete lineages with a wide range of pigmentation. In this review, we put our current knowledge of marine picocyanobacterial genomics into an environmental context and present previously unpublished genomic information arising from extensive genomic comparisons in order to provide insights into the adaptations of these marine microbes to their environment and how they are reflected at the genomic level.

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“…One candidate for such an accessory factor was RpaB, a similar OmpR-type response regulator. RpaA and RpaB were initially identified as regulators related to phycobilisome association in photosynthetic complexes (23), and RpaB was recently found to contribute to high light-dependent transcriptional regulation by binding to a specific DNA sequence known as the high light regulatory 1 (HLR1) element (18,24). However, a functional role for RpaB in circadian clock-dependent transcriptional regulation has not previously been proposed; the possibility that RpaB might function in circadian output pathways was not examined in a previous genetic screen because RpaB is an essential response regulator in Synechococcus (16).…”

Section: Rpaa Is Not Involved In Direct Transcriptional Regulation Ofmentioning

confidence: 99%

RpaB, Another Response Regulator Operating Circadian Clock-dependent Transcriptional Regulation in Synechococcus elongatus PCC 7942

Hanaoka

Takai

Hosokawa

et al. 2012

Journal of Biological Chemistry

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Background:The circadian output pathway in cyanobacteria is mediated by a two-component system consisting of SasA/RpaA. Results: An additional response regulator, RpaB, directly binds to clock-regulated promoters during the night. Conclusion: RpaB is also a key regulator of the circadian output pathway; RpaA and RpaB function cooperatively. Significance: Clarification of output pathway details is crucial for understanding the circadian clock.

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Cyanobacterial ycf27 gene products regulate energy transfer from phycobilisomes to photosystems I and II

Cited by 30 publications

References 13 publications

Redox crisis underlies conditional light–dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA

Redox crisis underlies conditional light–dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA

Ecological Genomics of Marine Picocyanobacteria

RpaB, Another Response Regulator Operating Circadian Clock-dependent Transcriptional Regulation in Synechococcus elongatus PCC 7942

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