Inorganic Phosphate Concentration in the Stroma of Isolated Chloroplasts and Its Influence on Photosynthesis

Robinson, SP; Giersch, Christoph

doi:10.1071/pp9870451

Cited by 29 publications

(22 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the metabolic signal responsible for regulation of the ATP synthase is not yet known, a well-established model involves modulation by changes in stromal P i concentrations (Robinson and Giersch 1987;Sharkey 1990;Takizawa et al 2007). If this model is relevant to C 4 plant chloroplasts, then changes in chloroplast P i levels would control ATP synthase conductance in response to changes Fig.…”

Section: Discussionmentioning

confidence: 99%

Co-regulation of dark and light reactions in three biochemical subtypes of C4 species

2010

View full text Add to dashboard Cite

Regulation of light harvesting in response to changes in light intensity, CO(2) and O(2) concentration was studied in C(4) species representing three different metabolic subtypes: Sorghum bicolor (NADP-malic enzyme), Amaranthus edulis (NAD-malic enzyme), and Panicum texanum (PEP-carboxykinase). Several photosynthetic parameters were measured on the intact leaf level including CO(2) assimilation rates, O(2) evolution, photosystem II activities, thylakoid proton circuit and dissipation of excitation energy. Gross rates of O(2) evolution (J(O)₂'), measured by analysis of chlorophyll fluorescence), net rates of O(2) evolution and CO(2) assimilation responded in parallel to changes in light and CO(2) levels. The C(4) subtypes had similar energy requirements for photosynthesis since there were no significant differences in maximal quantum efficiencies for gross rates of O(2) evolution (average value = 0.072 O(2)/quanta absorbed, approximately 14 quanta per O(2) evolved). At saturating actinic light intensities, when photosynthesis was suppressed by decreasing CO(2), ATP synthase proton conductivity (g (H) (+)) responded strongly to changes in electron flow, decreasing linearly with J(O)₂', which was previously observed in C(3) plants. It is proposed that g (H) (+) is controlled at the substrate level by inorganic phosphate availability. The results suggest development of nonphotochemical quenching in C(4) plants is controlled by a decrease in g (H) (+), which causes an increase in proton motive force by restricting proton efflux from the lumen, rather than by cyclic or pseudocyclic electron flow.

show abstract

Section: Discussionmentioning

confidence: 99%

Co-regulation of dark and light reactions in three biochemical subtypes of C4 species

2010

View full text Add to dashboard Cite

show abstract

“…For this reason, we have determined the bulk of phosphate esters in nonaqueously isolated chloroplasts. Knowing that inorganic phosphate concentrations are very low at high rates of photosynthesis in the presence of high CO2 concentrations (Walker and Sivak 1986;Robinson and Giersch 1987) and that total phosphate contents (organic plus inorganic phosphate) can be considered constant within the time scale of our experiments owing to the obligatory countertransport of phosphate and phosphate esters which is catalyzed by the phosphate translocator of the chloroplast envelope, we have assumed the total phosphate concentration in our sunflower chloroplasts to be 30 mM (see Dietz and Heber 1989). Subtraction of measured organic phosphates from this yields concentrations of inorganic phosphate.…”

Section: Still It Is Obvious Frommentioning

confidence: 99%

Control of photosynthesis in leaves as revealed by rapid gas exchange and measurements of the assimilatory force FA

Siebke

Laisk²,

Oja³

et al. 1990

Planta

View full text Add to dashboard Cite

The rapid transients of CO2 gas exchange have been measured in leaves ofHelianthus annuus L. In parallel experiments the assimilatory force FA, which is the product of the phosphorylation potential and the redox ratio NADPH/NADP, has been calculated from measured ratios of dihydroxyacetone phosphate to phosphoglycerate in the chloroplast stroma and in leaves. The following results were obtained: (i) When the light-dependent stroma alkalization was measured under steady-state conditions for photosynthesis in air containing 2000 μl · l(-1) CO2, alkalization increased with photosynthesis as the quantum flux density (irradiance) was increased. This contrasts to the light-dependent stroma alkalisation measured in dark-adapted leaves during the dark-light transient (Laisk et al. 1989, Planta177, 350-358) which reached a maximum at a quantum flux density far below that necessary to saturate photosynthesis. This maximum was about three times higher than the maximum stroma alkalization at light- and CO2-saturated photosynthesis. (ii) Accurate calculations of the assimilatory force FA require a consideration of the stromal pH. However, under many conditions, changes in the stromal pH resulting from changes in photosynthetic flux can be neglected because they are small. (iii) Stromal ratios of dihydroxyacetone phosphate to phosphoglycerate are generally lower than ratios measured in leaf extracts. The value of FA calculated from stromal metabolites was about 30% lower than FA calculated from cellular metabolites. Still, it appears sufficient for many purposes to calculate FA from metabolite measurements in leaf extracts. (iv) In the light, the catalytic capacity of the photosynthetic apparatus is adjusted to the level of irradiance. The response of carbon assimilation to large increases in irradiance is slow because it requires enzyme activation. Deactivation of the Calvin cycle induced by decreases in irradiance is slower than activation. (v) Changes in catalytic capacity and in the availability or level of substrates such as CO2 alter the flux resistance of the Calvin cycle. A decrease in flux resistance explains why FA often does not increase by much and may actually decrease when carbon flux is increased. Adjustments of flux resistances in the Calvin cycle and of photosystem-II activity in the electron-transport chain permit varying rates of photosynthesis at low levels of ATP and NADPH. As NADP remains available, the danger of over-reduction which leads to photoinactivation of electron transport is minimized.

show abstract

“…(i) The K m value in thylakoids, at least in the case of P i , may be the same, if not much lower, than the one obtained in the E. coli system, as in the case of the thylakoid ATP/ADP carrier (6). (ii) To accurately determine the P i concentration in organelles such as chloroplast (stroma) seems to be difficult; thus, values ranging between Յ1 and ϳ10 mM have been reported (27)(28)(29). (iii) When it comes to Na ϩ , its physiological concentration in the stroma is ϳ100 mM (30).…”

Section: Eantr1 Controlmentioning

confidence: 99%

Arabidopsis ANTR1 Is a Thylakoid Na+-dependent Phosphate Transporter

Pavón

Lundh²,

Lundin

et al. 2008

Journal of Biological Chemistry

View full text Add to dashboard Cite

In this study, the putative anion transporter 1 (ANTR1) from Arabidopsis thaliana was shown to be localized to the chloroplast thylakoid membrane by Western blotting with two different peptide-specific antibodies. ANTR1 is homologous to the type I of mammalian Na ؉ -dependent inorganic phosphate (P i ) transporters. The function of ANTR1 as a Na ؉ -dependent P i transporter was demonstrated by heterologous expression and uptake of radioactive P i into Escherichia coli cells. The expression of ANTR1 conferred increased growth rates to the transformed cells and stimulated P i uptake in a pH-and Na ؉ -dependent manner as compared with the control cells. Among various tested effectors, P i was the preferred substrate. Although it competed with the uptake of P i , glutamate was not transported by ANTR1 into E. coli. In relation to its function as a P i transporter, several physiological roles for ANTR1 in the thylakoid membrane are proposed, such as export of P i produced during nucleotide metabolism in the thylakoid lumen back to the chloroplast stroma and balance of the trans-thylakoid H ؉ electrochemical gradient storage.Solute and metabolite transporters play essential roles in physiological processes, including nutrient uptake, cell homeostasis, signal transduction, growth, and stress responses in every living organism. In the plant chloroplast, the photosynthetic organelle, most transporters have been identified and biochemically characterized from the envelope membrane (1, 2). Among them, there are several translocators for inorganic phosphate (P i ), all functioning as antiport systems using P i or phosphorylated C3 and C6 compounds as counter substrates (3, 4). Much less information is available for transport processes across the chloroplast thylakoid membrane, which is mostly studied as the site of light-driven photosynthetic reactions coupled to ATP synthesis. Only a few thylakoid transporters have been identified and functionally characterized. Examples are ATP transport across spinach thylakoid membrane into the lumenal space and a thylakoid ATP/ADP carrier identified and characterized in Arabidopsis thaliana (5,6). An active nucleotide metabolism in the thylakoid lumen (5) implies the existence of additional, yet unidentified, transporters, such as those recycling P i to the soluble stroma.A few Na ϩ -coupled P i transporters (NaP i ) 6 have in recent years been reported in green algae and vascular plants (7,8). NaP i systems are known to be mostly active in mammals, whereas H ϩ -coupled P i transport is dominant in plants (4). Three NaP i types have been described in eukaryotes, NaP i -II and III being the main ones in mammals (9 -11). NaP i -II type plays the role of an intracellular P i accumulation system, whereas NaP i -III type has the characteristics of a housekeeping system (9). The molecular mechanisms controlling the NaP i -II and III uptake systems have recently been reviewed (11). NaP i -I represents a group of proteins for which the endogenous substrate, ionic coupling, and physiological fu...

show abstract

Inorganic Phosphate Concentration in the Stroma of Isolated Chloroplasts and Its Influence on Photosynthesis

Cited by 29 publications

References 24 publications

Co-regulation of dark and light reactions in three biochemical subtypes of C4 species

Co-regulation of dark and light reactions in three biochemical subtypes of C4 species

Control of photosynthesis in leaves as revealed by rapid gas exchange and measurements of the assimilatory force FA

Arabidopsis ANTR1 Is a Thylakoid Na+-dependent Phosphate Transporter

Contact Info

Product

Resources

About