Phycobilisome rod mutants in Synechocystis sp. strain PCC6803

Ughy, Bettina; Ajlani, Ghada

doi:10.1099/mic.0.27498-0

Cited by 69 publications

(93 citation statements)

References 38 publications

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“…S4). 28,29 It appears that quenching of a core unit (Fig. 3, black and blue curves) occurred more frequently than quenching of a PC subunit (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Intact PB as well as PB cores and cores with short rods, and rod fractions were purified from WT Synechocystis and CK, 29 CB, 28 and ∆AB 27 mutants as reported before in Ref. 19, The samples were prepared for the single molecule experiments by a means of serial dilution and immobilization on a microscope cover glass (see SI for details).…”

Section: Experimental Section Summarymentioning

confidence: 99%

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Controlling Light Harvesting with Light

et al. 2016

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When exposed to intense sunlight all organisms performing oxygenic photosynthesis implement various photoprotective strategies to prevent potentially lethal photodamage. The rapidly responding photoprotective mechanisms, occurring in the light-harvesting pigment-protein antennae, take effect within tens of seconds, while the dramatic and potentially harmful light intensity fluctuations manifest also on shorter timescales. Here we show that upon illumination, individual phycobilisomes from Synechocystis PCC 6803, which in vivo under low-light conditions harvest solar energy, have the inbuilt capacity to switch rapidly and reversibly into light-activated energy-dissipating states. Simultaneously measured fluorescence intensity, lifetime and spectra, compared with a multi-compartmental kinetic model, revealed that essentially any subunit of a phycobilisome can be quenched, and that the core complexes were targeted most frequently. Our results provide the first evidence for fluorescence blinking from a biologically active system at physiological light intensities and suggest that the light-controlled switches to intrinsically available energy dissipating states are responsible for a novel type of photoprotection in cyanobacteria. We anticipate other photosynthetic organisms to employ similar strategies to respond instantly to rapid solar light intensity fluctuations. A detailed understanding of the photophysics of photosynthetic antenna complexes is of great interest for bioinspired solar energy technologies.

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“…S4). 28,29 It appears that quenching of a core unit (Fig. 3, black and blue curves) occurred more frequently than quenching of a PC subunit (Fig.…”

Section: Resultsmentioning

confidence: 99%

Section: Experimental Section Summarymentioning

confidence: 99%

Controlling Light Harvesting with Light

et al. 2016

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“…strain PCC 7120 and derivative strains were grown photoautotrophically at 30°C under constant white light (35 μE m −2 s −1 ), in a CO 2 enriched atmosphere. The medium composition is similar to BG11 with some modification (35). For heterocyst induction, cells were harvested by centrifugation and resuspended in NO 3 − deficient medium, for which NaNO 3 was replaced by NaCl.…”

Section: Methodsmentioning

confidence: 99%

Requirement of Fra proteins for communication channels between cells in the filamentous nitrogen-fixing cyanobacteriumAnabaenasp. PCC 7120

Omairi-Nasser

Mariscal

Austin

et al. 2015

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

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The filamentous nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120 differentiates specialized cells, heterocysts, that fix atmospheric nitrogen and transfer the fixed nitrogen to adjacent vegetative cells. Reciprocally, vegetative cells transfer fixed carbon to heterocysts. Several routes have been described for metabolite exchange within the filament, one of which involves communicating channels that penetrate the septum between adjacent cells. Several fra gene mutants were isolated 25 y ago on the basis of their phenotypes: inability to fix nitrogen and fragmentation of filaments upon transfer from N+ to N− media. Cryopreservation combined with electron tomography were used to investigate the role of three fra gene products in channel formation. FraC and FraG are clearly involved in channel formation, whereas FraD has a minor part. Additionally, FraG was located close to the cytoplasmic membrane and in the heterocyst neck, using immunogold labeling with antibody raised to the N-terminal domain of the FraG protein.

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“…Antenna mutants were maintained with added antibiotics as described previously (Ajlani and Vernotte, 1998;Ughy and Ajlani, 2004). For all experiments, antibiotics were omitted and samples were grown for 3 to 5 d.…”

Section: Growth Of Cyanobacterial Culturesmentioning

confidence: 99%

Photosynthetic Pigment Localization and Thylakoid Membrane Morphology Are Altered in Synechocystis 6803 Phycobilisome Mutants

et al. 2012

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(M.L., H.B.P.) Cyanobacteria are oxygenic photosynthetic prokaryotes that are the progenitors of the chloroplasts of algae and plants. These organisms harvest light using large membrane-extrinsic phycobilisome antenna in addition to membrane-bound chlorophyllcontaining proteins. Similar to eukaryotic photosynthetic organisms, cyanobacteria possess thylakoid membranes that house photosystem (PS) I and PSII, which drive the oxidation of water and the reduction of NADP + , respectively. While thylakoid morphology has been studied in some strains of cyanobacteria, the global distribution of PSI and PSII within the thylakoid membrane and the corresponding location of the light-harvesting phycobilisomes are not known in detail, and such information is required to understand the functioning of cyanobacterial photosynthesis on a larger scale. Here, we have addressed this question using a combination of electron microscopy and hyperspectral confocal fluorescence microscopy in wild-type Synechocystis species PCC 6803 and a series of mutants in which phycobilisomes are progressively truncated. We show that as the phycobilisome antenna is diminished, large-scale changes in thylakoid morphology are observed, accompanied by increased physical segregation of the two photosystems. Finally, we quantified the emission intensities originating from the two photosystems in vivo on a per cell basis to show that the PSI:PSII ratio is progressively decreased in the mutants. This results from both an increase in the amount of photosystem II and a decrease in the photosystem I concentration. We propose that these changes are an adaptive strategy that allows cells to balance the light absorption capabilities of photosystems I and II under light-limiting conditions.

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Phycobilisome rod mutants in Synechocystis sp. strain PCC6803

Cited by 69 publications

References 38 publications

Controlling Light Harvesting with Light

Controlling Light Harvesting with Light

Requirement of Fra proteins for communication channels between cells in the filamentous nitrogen-fixing cyanobacteriumAnabaenasp. PCC 7120

Photosynthetic Pigment Localization and Thylakoid Membrane Morphology Are Altered in Synechocystis 6803 Phycobilisome Mutants

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