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

Kiirats, Olavi; Kramer, David; Edwards, Gerald E.

doi:10.1007/s11120-010-9561-9

Cited by 16 publications

(19 citation statements)

References 34 publications

(47 reference statements)

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“…The value of g Hϩ at ambient CO 2 was approximately 25-30% higher in wild-type than either mothra or the complemented lines under all conditions, possibly reflecting slight differences in overall activity. However, decreasing CO 2 levels from ambient to 50 or near 0 ppm resulted in similar, strong decreases in g Hϩ in all lines, quantitatively similar to the effects reported earlier for Arabidopsis (34), tobacco (20), or a range of C 4 plants (22). Increasing CO 2 to 2000 ppm also resulted in similar decreases in g Hϩ in wildtype, mothra, and complemented lines.…”

Section: Atp Synthase In Mothra Is Equally Active In the Light-andsupporting

confidence: 86%

“…Increasing CO 2 to 2000 ppm also resulted in similar decreases in g Hϩ in wildtype, mothra, and complemented lines. This high CO 2 effect was reported earlier and ascribed to feedback limitations related to depletion of stromal inorganic phosphate (22,29). Overall, these results indicate that, whereas the ATP synthase in mothra is deficient in redox regulation, its responses to metabolic changes were essentially unaffected.…”

Section: Atp Synthase In Mothra Is Equally Active In the Light-andsupporting

confidence: 82%

“…in response to changing CO 2 , O 2 , or mutations that affect assimilation (20,22,27). This metabolism-related regulation modulates the thylakoid pmf (27,29), thus affecting the regulation of light capture and subsequent electron transfer.…”

Section: Atp Synthase In Mothra Is Equally Active In the Light-andmentioning

confidence: 99%

“…by decreasing atmospheric CO 2 or O 2 levels (20), imposing environmental stress conditions (e.g. drought) (21), or altering the capacity of the Calvin-Benson cycle and starch synthesis (22)(23)(24). It has thus been proposed that ATP synthase modulation represents an important feedback regulatory mechanism, sensing the metabolic status of the stroma and, in response, adjusting the efflux of protons from the lumen to modulate the lumen pH-dependent down-regulation of light capture and electron transfer.…”

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confidence: 99%

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Light- and Metabolism-related Regulation of the Chloroplast ATP Synthase Has Distinct Mechanisms and Functions

Kohzuma

Bosco

Meurer

et al. 2013

Journal of Biological Chemistry

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Background: Chloroplast ATP synthase activity is regulated by both light and metabolic factors, but the relationship between these regulatory modes is not established. Results: Mutating three highly conserved acidic amino acid residues in the ␥ subunit alters light-but not metabolism-induced regulation. Conclusion: Metabolism and light regulation operates via distinct mechanisms. Significance: The chloroplast ATP synthase is a key control point for the light and dark reactions of photosynthesis.

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Section: Atp Synthase In Mothra Is Equally Active In the Light-andsupporting

confidence: 86%

Section: Atp Synthase In Mothra Is Equally Active In the Light-andsupporting

confidence: 82%

Section: Atp Synthase In Mothra Is Equally Active In the Light-andmentioning

confidence: 99%

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confidence: 99%

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Light- and Metabolism-related Regulation of the Chloroplast ATP Synthase Has Distinct Mechanisms and Functions

Kohzuma

Bosco

Meurer

et al. 2013

Journal of Biological Chemistry

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“…Measurements were performed with a LI-COR 6400 gas-exchange analyzer coupled to a nonfocusing optics spectrophotometer/chlorophyll fluorometer (Avenson et al, 2004(Avenson et al, , 2005Kiirats et al, 2010). In brief, 0.79 cm 2 of leaf was clamped into a custom-built leaf chamber that allowed simultaneous measurements of net CO 2 exchange, chlorophyll fluorescence, and leaf optical properties.…”

Section: Chlorophyll a Fluorescence And Ecsmentioning

confidence: 99%

The Coordination of C4 Photosynthesis and the CO2-Concentrating Mechanism in Maize and Miscanthus × giganteus in Response to Transient Changes in Light Quality

et al. 2014

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Unequal absorption of photons between photosystems I and II, and between bundle-sheath and mesophyll cells, are likely to affect the efficiency of the CO 2 -concentrating mechanism in C 4 plants. Under steady-state conditions, it is expected that the biochemical distribution of energy (ATP and NADPH) and photosynthetic metabolite concentrations will adjust to maintain the efficiency of C 4 photosynthesis through the coordination of the C 3 (Calvin-Benson-Bassham) and C 4 (CO 2 pump) cycles. However, under transient conditions, changes in light quality will likely alter the coordination of the C 3 and C 4 cycles, influencing rates of CO 2 assimilation and decreasing the efficiency of the CO 2 -concentrating mechanism. To test these hypotheses, we measured leaf gas exchange, leaf discrimination, chlorophyll fluorescence, electrochromatic shift, photosynthetic metabolite pools, and chloroplast movement in maize (Zea mays) and Miscanthus 3 giganteus following transitional changes in light quality. In both species, the rate of net CO 2 assimilation responded quickly to changes in light treatments, with lower rates of net CO 2 assimilation under blue light compared with red, green, and blue light, red light, and green light. Under steady state, the efficiency of CO 2 -concentrating mechanisms was similar; however, transient changes affected the coordination of C 3 and C 4 cycles in M. giganteus but to a lesser extent in maize. The species differences in the ability to coordinate the activities of C 3 and C 4 cycles appear to be related to differences in the response of cyclic electron flux around photosystem I and potentially chloroplast rearrangement in response to changes in light quality.

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The single-process biochemical reaction of Rubisco: A unified theory and model with the effects of irradiance, CO2 and rate-limiting step on the kinetics of C3 and C4 photosynthesis from gas exchange

Farazdaghi¹

2011

Biosystems

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Photosynthesis is the origin of oxygenic life on the planet, and its models are the core of all models of plant biology, agriculture, environmental quality and global climate change. A theory is presented here, based on single process biochemical reactions of Rubisco, recognizing that: In the light, Rubisco activase helps separate Rubisco from the stored ribulose-1,5-bisphosphate (RuBP), activates Rubisco with carbamylation and addition of Mg²(+), and then produces two products, in two steps: (Step 1) Reaction of Rubisco with RuBP produces a Rubisco-enediol complex, which is the carboxylase-oxygenase enzyme (Enco) and (Step 2) Enco captures CO₂ and/or O₂ and produces intermediate products leading to production and release of 3-phosphoglycerate (PGA) and Rubisco. PGA interactively controls (1) the carboxylation-oxygenation, (2) electron transport, and (3) triosephosphate pathway of the Calvin-Benson cycle that leads to the release of glucose and regeneration of RuBP. Initially, the total enzyme participates in the two steps of the reaction transitionally and its rate follows Michaelis-Menten kinetics. But, for a continuous steady state, Rubisco must be divided into two concurrently active segments for the two steps. This causes a deviation of the steady state from the transitional rate. Kinetic models are developed that integrate the transitional and the steady state reactions. They are tested and successfully validated with verifiable experimental data. The single-process theory is compared to the widely used two-process theory of Farquhar et al. (1980. Planta 149, 78-90), which assumes that the carboxylation rate is either Rubisco-limited at low CO₂ levels such as CO₂ compensation point, or RuBP regeneration-limited at high CO₂. Since the photosynthesis rate cannot increase beyond the two-process theory's Rubisco limit at the CO₂ compensation point, net photosynthesis cannot increase above zero in daylight, and since there is always respiration at night, it leads to progressively negative daily CO₂ fixation with no possibility of oxygenic life on the planet. The Rubisco-limited theory at low CO₂ also contradicts all experimental evidence for low substrate reactions, and for all known enzymes, Rubisco included.

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

Cited by 16 publications

References 34 publications

Light- and Metabolism-related Regulation of the Chloroplast ATP Synthase Has Distinct Mechanisms and Functions

Light- and Metabolism-related Regulation of the Chloroplast ATP Synthase Has Distinct Mechanisms and Functions

The Coordination of C4 Photosynthesis and the CO2-Concentrating Mechanism in Maize and Miscanthus × giganteus in Response to Transient Changes in Light Quality

The single-process biochemical reaction of Rubisco: A unified theory and model with the effects of irradiance, CO2 and rate-limiting step on the kinetics of C3 and C4 photosynthesis from gas exchange

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