The PsbY Protein Is Not Essential for Oxygenic Photosynthesis in the Cyanobacterium <i>Synechocystis</i> sp. PCC 6803

Meetam, Metha; Keren, Nir; Ohad, Itzhak; Pakrasi, Himadri B.

doi:10.1104/pp.121.4.1267

Cited by 40 publications

(29 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Oocyte Membrane Extraction and Immunoblotting-For each sample, 10 oocytes were homogenized together by pipetting up and down in hypotonic lysis buffer (7.5 mM sodium phosphate, 1 mM EDTA, pH 7.5) containing a protease inhibitor mixture (Sigma-Aldrich) (19). The oocyte yolk was removed by discarding the pellet after a centrifugation at 735 ϫ g and 4°C for 10 min.…”

Section: Methodsmentioning

confidence: 99%

Plasma Membrane Aquaporin AqpZ Protein Is Essential for Glucose Metabolism during Photomixotrophic Growth of Synechocystis sp. PCC 6803

Akai

Onai

Kusano

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

The genome of Synechocystis PCC 6803 contains a single gene encoding an aquaporin, aqpZ. The AqpZ protein functioned as a water-permeable channel in the plasma membrane. However, the physiological importance of AqpZ in Synechocystis remains unclear. We found that growth in glucose-containing medium inhibited proper division of ⌬aqpZ cells and led to cell death. Deletion of a gene encoding a glucose transporter in the ⌬aqpZ background alleviated the glucose-mediated growth inhibition of the ⌬aqpZ cells. The ⌬aqpZ cells swelled more than the wild type after the addition of glucose, suggesting an increase in cytosolic osmolarity. This was accompanied by a down-regulation of the pentose phosphate pathway and concurrent glycogen accumulation. Metabolite profiling by GC/TOF-MS of wild-type and ⌬aqpZ cells revealed a relative decrease of intermediates of the tricarboxylic acid cycle and certain amino acids in the mutant. The changed levels of metabolites may have been the cause for the observed decrease in growth rate of the ⌬aqpZ cells along with decreased PSII activity at pH values ranging from 7.5 to 8.5. A mutant in sll1961, encoding a putative transcription factor, and a ⌬hik31 mutant, lacking a putative glucose-sensing kinase, both exhibited higher glucose sensitivity than the ⌬aqpZ cells. Examination of protein expression indicated that sll1961 functioned as a positive regulator of aqpZ gene expression but not as the only regulator. Overall, the ⌬aqpZ cells showed defects in macronutrient metabolism, pH homeostasis, and cell division under photomixotrophic conditions, consistent with an essential role of AqpZ in glucose metabolism.

show abstract

Section: Methodsmentioning

confidence: 99%

Plasma Membrane Aquaporin AqpZ Protein Is Essential for Glucose Metabolism during Photomixotrophic Growth of Synechocystis sp. PCC 6803

Akai

Onai

Kusano

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Flash-induced Oxygen Yield-Flash-induced oxygen yield of cyanobacterial cells was measured after dark adaptation for 7 min using a home-built, bare-platinum, Joliot-type electrode as described (18). For the estimation of the rates of decay of the S 2 or S 3 states, the cells were exposed to 1 or 2 single turnover exciting flashes (EG&G, LS-11340 -4, 6 s duration), respectively, followed by additional flashes after increasing time intervals, and the oxygen yield at the third flash was measured.…”

Section: Methodsmentioning

confidence: 99%

Deregulation of Electron Flow within Photosystem II in the Absence of the PsbJ Protein

Regel¹,

Ivleva²,

Zer³

et al. 2001

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

The photosystem II (PSII) complex of photosynthetic oxygen evolving membranes comprises a number of small proteins whose functions remain unknown. Here we report that the low molecular weight protein encoded by the psbJ gene is an intrinsic component of the PSII complex. Fluorescence kinetics, oxygen flash yield, and thermoluminescence measurements indicate that inactivation of the psbJ gene in Synechocystis 6803 cells and tobacco chloroplasts lowers PSII-mediated oxygen evolution activity and increases the lifetime of the reduced primary acceptor Q A Ϫ (more than a 100-fold in the tobacco ⌬psbJ mutant). The decay of the oxidized S 2,3 states of the oxygen-evolving complex is considerably accelerated, and the oscillations of the Q B Ϫ /S 2,3 recombination with the number of exciting flashes are damped. Thus, PSII can be assembled in the absence of PsbJ. However, the forward electron flow from Q A Ϫ to plastoquinone and back electron flow to the oxidized Mn cluster of the donor side are deregulated in the absence of PsbJ, thereby affecting the efficiency of PSII electron flow following the charge separation process. The photosystem II complex (PSII)1 of the thylakoid membrane is involved in the photochemical process resulting in water oxidation, oxygen evolution, and reduction of plastoquinone. PSII comprises a core complex formed by a few proteins binding the ligands required for primary photochemistry and electron transfer and the chlorophyll-binding antennae as well as a number of low molecular weight proteins whose functions have not yet been identified (1, 2). The process of light-induced charge separation and reduction of a quinone acceptor, similar to that performed by PSII, is also carried out by photosynthetic bacteria that do not evolve oxygen and perform cyclic electron flow around the bacterial photochemical reaction center (RC) (3). While in both cases a small number of proteins binding the appropriate ligands are capable of light-driven charge separation and electron transfer, the linear electron flow performed by PSII using water as a source of electrons is more complex and may require regulatory steps that are not demanded by the cyclic electron flow of the bacterial RC. Thus it is plausible that proteins of PSII, besides those acting as energy-transferring antennae (4), may play some role in the regulation of the forward and backward electron flow within the PSII core complex. Recombination of the primary charge-separated pair due to back electron flow may lead to the generation of singlet oxygen considered to be the cause of PSII oxidative stress and turnover of its core proteins (5, 6). Indeed cytochrome b 559 , an essential component of the PSII core complex is considered to play such a regulatory role by diverting electrons from the reducing side of PSII and channeling them to the oxidized donor side of the complex (7). This protein is missing from the RC complex of purple anoxygenic photosynthetic bacteria. The psbE and psbF genes encoding the ␣ and ␤ subunits of cytochrome b 559 , respectiv...

show abstract

“…Figure 2 shows the chlorophyll fluorescence decay kinetics in 20-and 40-day-old leaves of the wild type and ppt1 mutant. Under normal conditions, after a single flash, the largest contribution to the chlorophyll decay kinetics is typically electron transfer from Q A -to the secondary electron acceptor Q B (Trìlek et al 1997;Diner 1998;Meetam et al 1999) and the Youngest and old leaves, illustrated by the red and black dotted lines, were not included in the analyses. Leaves of 6-week-old plants were pooled into young (leaves 1-6; orange thread) and mature (leaves 7-12; blue thread) groups.…”

Section: Fluorescence Decay Kinetics Of the Ppt1 Mutantmentioning

confidence: 99%

Decrease of Photosystem II Photochemistry in Arabidopsis ppt1 Mutant Is Dependent on Leaf Age

Guo

Peng

et al. 2006

JIPB

View full text Add to dashboard Cite

In the present study, we compared the effect of leaf age at one development stage on the photosynthetic behavior of a T-DNA-tagged allele of the ppt1 mutant. Chlorophyll fluorescence (F v /F m , where F m is the maximum fluorescence yield and F v is variable fluorescence) and fluorescence decay kinetics of the ppt1 mutant were different in leaves of different ages. The steady state levels of thylakoid membrane proteins in 40-day-old leaves were decreased compared with those in 20-day-old leaves and changes in photosystem (PS) II proteins were correlated with those of the F v /F m ratio in the ppt1 mutant. Increased accumulation of leaf sugars was accompanied by decreased photosynthetic gene transcripts and protein content in 40-day-old leaves of the mutant. Thus, the results of the present study provide evidence for the phosphate translocator in maintaining normal photosynthesis at a late leaf age.Key words: Arabidopsis thaliana; leaf age; photosynthesis; photosystem II; ppt1 mutant. Photosynthesis is not only affected by plastid developmental stage, but also by several other metabolic processes. Mutation of a gene encoding a protein with a structural or regulatory function can interfere with chloroplast biogenesis or function, with photosynthesis, and finally, influence plant development. The Arabidopsis ppt1 (or cue1) mutant is defective in AtPPT1 (at5g33320), which has been isolated in a screen for chlorophyll a/b binding protein (CAB) underexpressors (Li et al. 1995; Knappe et al. 2003). The affected gene in cue1 is a phosphoenolpyruvate (PEP)/phosphate translocator (PPT) of the plastid inner envelope membrane (Streatfield et al. 1999). It appears that PEP is essential for plastid development and most nongreen plastids have been reported to be incapable of producing PEP from Calvin cycle intermediates (Flügge 1995; Voll et al. 2002). As a key metabolite, PEP acts as a precursor and intermediate for primary and secondary plant products via the shikimate pathway, which is profoundly important to plant life (Herrmann 1995;Fischer et al. 1997;Lara et al. 2002). Ma JF, Guo JK, Peng LW, Chen CY, Zhang LX (2006). Decrease of photosystem II photochemistry inPrevious studies have demonstrated that the ppt1 mutant is severely compromised in establishing photoautotrophic growth (Li et al. 1995). The morphological and gene underexpression phenotypes of ppt1 are light intensity dependent (Streatfield et al. 1999). The chlorophyll and carotenoid components of the light-harvesting and photoprotective machinery are also diminished in ppt1 (Knappe et al. 2003). Overexpression of heterologous PPT2 or orthophosphate dikinase (PPDK) can partially complement the phenotype of ppt1. Thus, the cue1 mutant phenotype cannot simply be explained by a general restriction of the supply of plastids with PEP via the PPT (López-Juez 1998;Streatfield et al. 1999;Voll et al. 2003).In the present study, we characterized a T-DNA-tagged allele of the ppt1 mutant that was selected on the basis of its high chlorophyll fluorescence phenot...

show abstract

The PsbY Protein Is Not Essential for Oxygenic Photosynthesis in the Cyanobacterium Synechocystis sp. PCC 6803

Cited by 40 publications

References 24 publications

Plasma Membrane Aquaporin AqpZ Protein Is Essential for Glucose Metabolism during Photomixotrophic Growth of Synechocystis sp. PCC 6803

Plasma Membrane Aquaporin AqpZ Protein Is Essential for Glucose Metabolism during Photomixotrophic Growth of Synechocystis sp. PCC 6803

Deregulation of Electron Flow within Photosystem II in the Absence of the PsbJ Protein

Decrease of Photosystem II Photochemistry in Arabidopsis ppt1 Mutant Is Dependent on Leaf Age

Contact Info

Product

Resources

About