A genetically engineered increase in fatty acid unsaturation in <i>Synechococcus</i> sp. PCC 7942 allows exchange of D1 protein forms and sustenance of photosystem II activity at low temperature

Sippola, Katja; Kanervo, Eira; Murata, Norio; Aro, Eva‐Mari

doi:10.1046/j.1432-1327.1998.2510641.x

Cited by 44 publications

(21 citation statements)

References 2 publications

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“…In turn, this may impact photosynthesis via several different mechanisms: (1) the change in membrane fluidity may affect the activity of membrane bound proteins, including those required for photosynthesis; (2) the change in chemical composition may disrupt the membrane structure itself, preventing formation of the thylakoid membranes; and (3) the increased saturation of FA may prevent the attachment of the light-harvesting phycobilisomes to the thylakoid membrane. The influence of fatty acid saturation on photosynthetic activity at low temperatures is well-documented (Gombos et al 1991; Gombos et al 1992; Sippola et al 1998), illustrating that membrane composition impacts enzymatic activities in cyanobacteria. The reduced photosynthetic yields for FFA-producing S. elongatus 7942 may correspond to reduced activity of photosynthetic enzymes.…”

Section: Discussionmentioning

confidence: 99%

Physiological effects of free fatty acid production in genetically engineered Synechococcus elongatus PCC 7942

Ruffing

Jones

2012

Biotech & Bioengineering

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Objective Hip flexion range of motion (ROM), hip extensor strength (torque production), and hip pain are important correlates of physical function in individuals with hip osteoarthritis (OA). However, the relationships among these variables remain unclear. The purpose of this study was to examine whether hip extensor strength and hip pain mediate the association between hip flexion ROM and physical function. Methods Participants were 100 adults (mean age 62 years) with radiographically confirmed hip OA. Passive hip flexion ROM was measured using a digital inclinometer, and isometric hip extensor strength was measured using a force transducer. Self‐report measures of physical function and pain were assessed by the Short Form 36 (SF‐36) questionnaire, and physical performance was assessed by the gait speed, step test, and stair climb test. Results Multiple mediation analyses, adjusted for demographic and anthropometric measures, revealed that the association between hip flexion ROM and SF‐36 physical function scores was fully mediated by SF‐36 bodily pain scores and hip extensor strength. Hip extensor strength mediated the hip flexion effects on gait speed and step test performance, while the SF‐36 bodily pain scores mediated the hip flexion stair performance association. Conclusion In individuals with symptomatic hip OA, hip pain and hip extensor strength mediated the influence of hip flexion ROM on physical function. These results suggest that interventions to improve the range of hip motion may be clinically indicated.

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Section: Discussionmentioning

confidence: 99%

Physiological effects of free fatty acid production in genetically engineered Synechococcus elongatus PCC 7942

Ruffing

Jones

2012

Biotech & Bioengineering

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“…Because cyanobacteria lack zeaxanthin cycle-dependent antenna quenching (45), the proposed mechanism of energy dissipation would be of primary importance in protecting cyanobacterial cells from photoinhibitory damage when PSII reaction centers are exposed to high excitation pressure induced by exposure to chilling temperatures. The transient exchange of the D1:1 protein, which appears to be the initial response, may thus provide the time required for full cellular acclimation to an increased excitation pressure through modifications in protein (2,6,10) and lipid (24,46) composition.…”

Section: Discussionmentioning

confidence: 99%

A Transient Exchange of the Photosystem II Reaction Center Protein D1:1 with D1:2 during Low Temperature Stress ofSynechococcus sp. PCC 7942 in the Light Lowers the Redox Potential of QB

Sane

Ivanov

Sveshnikov

et al. 2002

Journal of Biological Chemistry

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Upon exposure to low temperature under constant light conditions, the cyanobacterium Synechococcus sp. PCC 7942 exchanges the photosystem II reaction center D1 protein form 1 (D1:1) with D1 protein form 2 (D1:2). This exchange is only transient, and after acclimation to low temperature the cells revert back to D1:1, which is the preferred form in acclimated cells (Campbell, D., Zhou, G., Gustafsson, P., Ö quist, G., and Clarke, A. K. (1995) EMBO J. 14, 5457-5466). In the present work we use thermoluminescence to study charge recombination events between the acceptor and donor sides of photosystem II in relation to D1 replacement. The data indicate that in cold-stressed cells exhibiting D1:2, the redox potential of Q B becomes lower approaching that of Q A . This was confirmed by examining the Synechococcus sp. PCC 7942 inactivation mutants R2S2C3 and R2K1, which possess only D1:1 or D1:2, respectively. In contrast, the recombination of Q A ؊ with the S 2 and S 3 states did not show any change in their redox characteristics upon the shift from D1:1 to D1:2. We suggest that the change in redox properties of Q B results in altered charge equilibrium in favor of Q A . This would significantly increase the probability of Q A ؊ and P680 ؉ recombination. The resulting non-radiative energy dissipation within the reaction center of PSII may serve as a highly effective protective mechanism against photodamage upon excessive excitation. The proposed reaction center quenching is an important protective mechanism because antenna and zeaxanthin cycle-dependent quenching are not present in cyanobacteria. We suggest that lowering the redox potential of Q B by exchanging D1:1 for D1:2 imparts the increased resistance to high excitation pressure induced by exposure to either low temperature or high light.

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“…One prediction of this idea would be that the turnover of the D1 polypeptide should be slower in the desA ϩ transformant in which phycobilisome mobility is greatly reduced. However, it appears that D1 turnover is actually faster in desA ϩ than in the wild-type (36). Phycobilisome Mobility Increases the Efficiency of Light-harvesting-Phycobilisomes are mobile on the same time scale as the secondary electron transport reactions.…”

Section: Physiological Role(s) Of Phycobilisome Mobilitymentioning

confidence: 99%

Diffusion of Phycobilisomes on the Thylakoid Membranes of the Cyanobacterium Synechococcus 7942

Sarcina¹,

Tobin²,

Mullineaux³

2001

Journal of Biological Chemistry

123

106

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A variant of fluorescence recovery after photobleaching allows us to observe the diffusion of photosynthetic complexes in cyanobacterial thylakoid membranes in vivo. The unicellular cyanobacterium Synechococcus sp. PCC7942 is a wonderful model organism for fluorescence recovery after photobleaching, because it has a favorable membrane geometry and is well characterized and transformable. In Synechococcus 7942 (as in other cyanobacteria) we find that photosystem II is immobile, but phycobilisomes diffuse rapidly on the membrane surface. The diffusion coefficient is 3 ؋ 10 ؊10 cm 2 s ؊1 at 30°C. This shows that the association of phycobilisomes with reaction centers is dynamic; there are no stable phycobilisome-reaction center complexes in vivo. We report the effects of mutations that change the phycobilisome size and membrane lipid composition. 1) In a mutant with no phycobilisome rods, the phycobilisomes remain mobile with a slightly faster diffusion coefficient. This confirms that the diffusion we observe is of intact phycobilisomes rather than detached rod elements. The faster diffusion coefficient in the mutant indicates that the rate of diffusion is partly determined by the phycobilisome size. 2) The temperature dependence of the phycobilisome diffusion coefficient indicates that the phycobilisomes have no integral membrane domain. It is likely that association with the membrane is mediated by multiple weak interactions with lipid head groups. 3) Changing the lipid composition of the thylakoid membrane has a dramatic effect on phycobilisome mobility. The results cannot be explained in terms of changes in the fluidity of the membrane; they suggest that lipids play a role in controlling phycobilisome-reaction center interaction.

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A genetically engineered increase in fatty acid unsaturation in Synechococcus sp. PCC 7942 allows exchange of D1 protein forms and sustenance of photosystem II activity at low temperature

Cited by 44 publications

References 2 publications

Physiological effects of free fatty acid production in genetically engineered Synechococcus elongatus PCC 7942

Physiological effects of free fatty acid production in genetically engineered Synechococcus elongatus PCC 7942

A Transient Exchange of the Photosystem II Reaction Center Protein D1:1 with D1:2 during Low Temperature Stress ofSynechococcus sp. PCC 7942 in the Light Lowers the Redox Potential of QB

Diffusion of Phycobilisomes on the Thylakoid Membranes of the Cyanobacterium Synechococcus 7942

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