Phosphate (Pi) Starvation Effect on the Cytosolic Pi Concentration and Pi Exchanges across the Tonoplast in Plant Cells: An in Vivo 31P-Nuclear Magnetic Resonance Study Using Methylphosphonate as a Pi Analog

Pratt, Jon R.; Boisson, Anne-Marie; Gout, Elisabeth; Bligny, Richard; Douce, Roland; Aubert, S.

doi:10.1104/pp.109.144626

Cited by 117 publications

(144 citation statements)

References 56 publications

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“…Green arrows represent range of productive operating condition for each of the ATPases shown. Red circles represent examples of reported stoichiometry and physiological conditions (42,48,60,61,(63)(64)(65)(66)(67). The diagonal represents equilibrium behavior where the efficiency, as defined in the text, is maximum but the rate of synthesis or pumping would vanish.…”

Section: Kinetic Equivalence Of Pmf Components May Depend On Experimementioning

confidence: 99%

Biophysical comparison of ATP synthesis mechanisms shows a kinetic advantage for the rotary process

Anandakrishnan

Zhang

Donovan-Maiye

et al. 2016

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

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The ATP synthase (F-ATPase) is a highly complex rotary machine that synthesizes ATP, powered by a proton electrochemical gradient. Why did evolution select such an elaborate mechanism over arguably simpler alternating-access processes that can be reversed to perform ATP synthesis? We studied a systematic enumeration of alternative mechanisms, using numerical and theoretical means. When the alternative models are optimized subject to fundamental thermodynamic constraints, they fail to match the kinetic ability of the rotary mechanism over a wide range of conditions, particularly under low-energy conditions. We used a physically interpretable, closed-form solution for the steady-state rate for an arbitrary chemical cycle, which clarifies kinetic effects of complex free-energy landscapes. Our analysis also yields insights into the debated "kinetic equivalence" of ATP synthesis driven by transmembrane pH and potential difference. Overall, our study suggests that the complexity of the F-ATPase may have resulted from positive selection for its kinetic advantage.ATP synthase | kinetic mechanism | free-energy landscape | nonequilibrium steady state | evolution T he F-ATPase performs molecular-level free-energy (FE) transduction to phosphorylate ADP and yield ATP, the primary energy carrier that drives a vast range of cellular processes. It spurred Mitchell's chemiosmotic hypothesis (1) and Boyer's now-validated proposal for the binding-change mechanism (2) in which a proton electrochemical gradient is transduced to rotationbased mechanical energy and then back to chemical FE as ADP is phosphorylated. The F-ATPase's two-domain uniaxial rotary structure is conserved across all three domains of life (3-6), and details of its function have been the subject of a multitude of studies (e.g., refs. 7-30).Here, we address a relatively narrow question with potentially significant evolutionary implications: Why is ATP synthesized by a rotary mechanism instead of a potentially much simpler alternating-access mechanism (Fig. 1)? Using thermodynamic and kinetic constraints, we address the question of whether evolution tends to arrive at optimal molecular processes (31), building on established concepts of optimality-derived evolutionary convergence (32, 33). Presumably, performance advantages in the central task of ATP synthesis would be under significant evolutionary pressure. Previous modeling studies of the F-ATPase have addressed structural and mechanistic questions about the rotary mechanism (e.g., refs. 11-20), but not the metaissue of the mechanism itself compared with alternatives.To assess whether the rotary mechanism possesses any intrinsic performance advantage, we constructed a series of kinetic models abstracted from known mechanisms (Fig. 1). Beyond the rotarybased model, we considered a series of alternating-access analogs (Fig. 2), building on the demonstrated capacity for ATP-hydrolyzing transporters to be driven in reverse to synthesize ATP (34, 35). The discrete-state models do not include structural details, bu...

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Section: Kinetic Equivalence Of Pmf Components May Depend On Experimementioning

confidence: 99%

Biophysical comparison of ATP synthesis mechanisms shows a kinetic advantage for the rotary process

Anandakrishnan

Zhang

Donovan-Maiye

et al. 2016

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

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“…The level of E4P was estimated assuming that the TRK reaction with E4P and GAP is at equilibrium, and individual levels of Xu5P and Ru5P were estimated by assuming that RPE is at equilibrium. The D r G for the combined reactions of GAPDH and PGK was estimated using measured values of 3PGA and GAP, assuming an NADPH/NADP ratio of 1 (Heineke et al, 1991) and a P i concentration of 0.002 M (Pratt et al, 2009). Nonaqueous fractionation (Dietz and Heber, 1984) and subcellular fractionation by membrane filtration of chloroplasts have shown that the ATP/ ADP ratios in the plastid are much lower than those in the cytosol (Stitt et al, 1982;Gardeström and Wigge, 1988).…”

Section: Calculation Of Gibbs Free Energy Allows the Identification Omentioning

confidence: 99%

Systems Analysis of the Response of Photosynthesis, Metabolism, and Growth to an Increase in Irradiance in the Photosynthetic Model OrganismChlamydomonas reinhardtii

et al. 2014

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We investigated the systems response of metabolism and growth after an increase in irradiance in the nonsaturating range in the algal model Chlamydomonas reinhardtii. In a three-step process, photosynthesis and the levels of metabolites increased immediately, growth increased after 10 to 15 min, and transcript and protein abundance responded by 40 and 120 to 240 min, respectively. In the first phase, starch and metabolites provided a transient buffer for carbon until growth increased. This uncouples photosynthesis from growth in a fluctuating light environment. In the first and second phases, rising metabolite levels and increased polysome loading drove an increase in fluxes. Most Calvin-Benson cycle (CBC) enzymes were substrate-limited in vivo, and strikingly, many were present at higher concentrations than their substrates, explaining how rising metabolite levels stimulate CBC flux. Rubisco, fructose-1,6-biosphosphatase, and seduheptulose-1,7-bisphosphatase were close to substrate saturation in vivo, and flux was increased by posttranslational activation. In the third phase, changes in abundance of particular proteins, including increases in plastidial ATP synthase and some CBC enzymes, relieved potential bottlenecks and readjusted protein allocation between different processes. Despite reasonable overall agreement between changes in transcript and protein abundance (R 2 = 0.24), many proteins, including those in photosynthesis, changed independently of transcript abundance.

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“…The triple KO mutant and wild-type plants were analyzed by the 31 P NMR technique, which can detect several phosphoruscontaining compounds either in living plants or cell extracts (Bligny et al, 1990;Pratt et al, 2009). The drawback of this technique is that it requires large quantities of biological material.…”

Section: Triple Ko Mutant Does Not Mimic or Amplify Phenotypes Causedmentioning

confidence: 99%

The Phosphate Fast-Responsive Genes PECP1 and PPsPase1 Affect Phosphocholine and Phosphoethanolamine Content

et al. 2018

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Phosphate starvation-mediated induction of the HAD-type phosphatases PPsPase1 (AT1G73010) and PECP1 (AT1G17710) has been reported in Arabidopsis (Arabidopsis thaliana). However, little is known about their in vivo function or impact on plant responses to nutrient deficiency. The preferences of PPsPase1 and PECP1 for different substrates have been studied in vitro but require confirmation in planta. Here, we examined the in vivo function of both enzymes using a reverse genetics approach. We demonstrated that PPsPase1 and PECP1 affect plant phosphocholine and phosphoethanolamine content, but not the pyrophosphate-related phenotypes. These observations suggest that the enzymes play a similar role in planta related to the recycling of polar heads from membrane lipids that is triggered during phosphate starvation. Altering the expression of the genes encoding these enzymes had no effect on lipid composition, possibly due to compensation by other lipid recycling pathways triggered during phosphate starvation. Furthermore, our results indicated that PPsPase1 and PECP1 do not influence phosphate homeostasis, since the inactivation of these genes had no effect on phosphate content or on the induction of molecular markers related to phosphate starvation. A combination of transcriptomics and imaging analyses revealed that PPsPase1 and PECP1 display a highly dynamic expression pattern that closely mirrors the phosphate status. This temporal dynamism, combined with the wide range of induction levels, broad expression, and lack of a direct effect on Pi content and regulation, makes PPsPase1 and PECP1 useful molecular markers of the phosphate starvation response.Plant growth is highly sensitive to a lack of phosphate (Pi); hence, the application of Pi fertilizers has become standard practice for high-throughput crop production (Cordell et al., 2009). Most phosphorus in the soil is not available to plants, as it is combined with other minerals or parts of organic compounds (Bieleski, 1973;Raghothama and Karthikeyan, 2005). Only a small fraction of soluble Pi (usually present at a concentration of ,10 mM in the soil) can be taken up by plants.Although growth is not optimal under limiting conditions, plants can withstand changing Pi concentrations within heterogeneous soils or in the external nutrient supply that can lead to reprogramming of their metabolism and architecture (Hammond et al., 2003;Péret et al., 2011;Plaxton and Tran, 2011). Root architecture can be modified to facilitate Pi uptake by favoring the development of lateral roots (at the expense of primary root elongation in many plants including Arabidopsis), increasing the density and length of root hairs, and limiting the development of aerial parts (López-Bucio et al., 2002;Svistoonoff et al., 2007;Gruber et al., 2013). Pi uptake mechanisms are enhanced at the root/soil interface, particularly through the stimulation of Pi transport activity (Mudge et al., 2002;Shin et al., 2004;Nussaume et al., 2011; Ayadi et al., 2015). In parallel, mobilization of Pi sources fr...

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Phosphate (Pi) Starvation Effect on the Cytosolic Pi Concentration and Pi Exchanges across the Tonoplast in Plant Cells: An in Vivo 31P-Nuclear Magnetic Resonance Study Using Methylphosphonate as a Pi Analog

Cited by 117 publications

References 56 publications

Biophysical comparison of ATP synthesis mechanisms shows a kinetic advantage for the rotary process

Biophysical comparison of ATP synthesis mechanisms shows a kinetic advantage for the rotary process

Systems Analysis of the Response of Photosynthesis, Metabolism, and Growth to an Increase in Irradiance in the Photosynthetic Model OrganismChlamydomonas reinhardtii

The Phosphate Fast-Responsive Genes PECP1 and PPsPase1 Affect Phosphocholine and Phosphoethanolamine Content

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