Response: Commentary: Directions for Optimization of Photosynthetic Carbon Fixation: RuBisCO’s Efficiency May Not Be So Constrained After All

Cummins, Peter L.; Kannappan, Babu; Gready, Jill E.

doi:10.3389/fpls.2019.01426

Cited by 10 publications

(12 citation statements)

References 23 publications

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“…For each genus, the near-linear trend predicted in Figure 3A suggests performing the linear regression for S C vs. S O with the intercept fixed at zero ( Figure 4A ). Further, the gradient (regression coefficient) of the regression line in this way quite accurately predicts the sample S C/O means for each of the genera ( Figure 4B ), which again validates our basic assertion that the coefficients of the linear regression should correspond to sample means ( Cummins et al, 2018a , 2019a ). Examples of genera with data for more than a few species are rather limited.…”

Section: Resultssupporting

confidence: 81%

“…Compared to C 3 Limonium and C 4 plants, S C converges very quickly to this mean value for the C 3 sample ( Table 1 ), and so the dependence of K C on b , which depends on the decarboxylation rate ( k 6 ), may be neglected. This would suggest a lesser significance of k 6 in C 3 species, resolving to some extent the apparent differences of opinion on the issue of decarboxylation ( Tcherkez et al, 2018 ; Cummins et al, 2019a ). Nevertheless, the results suggest significant ( mV max ≈ b ) decarboxylation in both C 3 Limonium and C 4 samples ( Figure 1A ) and deoxygenation ( k 12 , i.e., breakdown of the Michaelis complex by dissociation of O 2 ) in all three ( Figure 1C ).…”

Section: Discussionmentioning

confidence: 95%

“…The coefficient of the K M intercept and coefficient of V max obtained by linear regression of the data can be interpreted as the sample mean values of b and m, respectively, which are functions of the rate constants for the elementary steps in the kinetic mechanism (Cummins et al, 2018a). Prior linear regression analysis of the explicit dependence of K M on V max indicates that K M is to some extent dependent on the value of b, which is a function of the dissociation rates (among other rate constants) of the CO 2 and O 2 gas substrates (Cummins et al, 2018a(Cummins et al, , 2019a.…”

Section: Methodsmentioning

confidence: 99%

“…Although the possibility of enhancing photosynthesis by improving RuBisCO kinetic traits has been given due consideration ( Whitney et al, 2011 ; Sharwood et al, 2016 ; Gomez-Fernandez et al, 2018 ; Wilson et al, 2018 ; Zhou and Whitney, 2019 ; Davidi et al, 2020 ; Lin et al, 2020 ; Bouvier et al, 2021 ), a conclusive picture of RuBisCO’s molecular mechanism ( Cleland et al, 1998 ; Tcherkez, 2013 , 2015 ; Cummins et al, 2018b , 2019b ; Kannappan et al, 2019 ; Bathellier et al, 2020 ; Cummins and Gready, 2020 ) and a general consensus understanding of the observed tradeoffs between RuBisCO’s kinetic parameters remains elusive, despite having been analyzed in varying ways with the objective of gaining insights into the possible connection between evolutionary and biochemical (or catalytic) constraints ( Bouvier et al, 2021 ). The earliest of these studies, ( Tcherkez et al, 2006 ; Savir et al, 2010 ) based on general mechanistic assumptions and limited data samples, concluded that variations in the elementary rate constants must be tightly constrained by the limitations inherent in RuBisCOs kinetic mechanism, resulting in an enzyme which provides only limited scope for further optimization ( Tcherkez et al, 2006 ; Tcherkez, 2013 , 2015 ), while later studies of more extensive data sets have challenged this view, revealing greater flexibility ( Cummins et al, 2018a , 2019a ; Flamholz et al, 2019 ). Other studies have examined the coevolution of RuBisCO kinetics and carbon concentrating mechanism (CCMs) ( Goudet et al, 2020 ; Iñiguez et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

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The Coevolution of RuBisCO, Photorespiration, and Carbon Concentrating Mechanisms in Higher Plants

Cummins

2021

Front. Plant Sci.

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Ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO) is the carbon-fixing enzyme present in most photosynthetic organisms, converting CO2 into organic matter. Globally, photosynthetic efficiency in terrestrial plants has become increasingly challenged in recent decades due to a rapid increase in atmospheric CO2 and associated changes toward warmer and dryer environments. Well adapted for these new climatic conditions, the C4 photosynthetic pathway utilizes carbon concentrating mechanisms to increase CO2 concentrations surrounding RuBisCO, suppressing photorespiration from the oxygenase catalyzed reaction with O2. The energy efficiency of C3 photosynthesis, from which the C4 pathway evolved, is thought to rely critically on an uninterrupted supply of chloroplast CO2. Part of the homeostatic mechanism that maintains this constancy of supply involves the CO2 produced as a byproduct of photorespiration in a negative feedback loop. Analyzing the database of RuBisCO kinetic parameters, we suggest that in genera (Flaveria and Panicum) for which both C3 and C4 examples are available, the C4 pathway evolved only from C3 ancestors possessing much lower than the average carboxylase specificity relative to that of the oxygenase reaction (SC/O=SC/SO), and hence, the higher CO2 levels required for development of the photorespiratory CO2 pump (C2 photosynthesis) essential in the initial stages of C4 evolution, while in the later stage (final optimization phase in the Flaveria model) increased CO2 turnover may have occurred, which would have been supported by the higher CO2 levels. Otherwise, C4 RuBisCO kinetic traits remain little changed from the ancestral C3 species. At the opposite end of the spectrum, C3 plants (from Limonium) with higher than average SC/O, which may be associated with the ability of increased CO2, relative to O2, affinity to offset reduced photorespiration and chloroplast CO2 levels, can tolerate high stress environments. It is suggested that, instead of inherently constrained by its kinetic mechanism, RuBisCO possesses the extensive kinetic plasticity necessary for adaptation to changes in photorespiration that occur in the homeostatic regulation of CO2 supply under a broad range of abiotic environmental conditions.

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Section: Resultssupporting

confidence: 81%

Section: Discussionmentioning

confidence: 95%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Coevolution of RuBisCO, Photorespiration, and Carbon Concentrating Mechanisms in Higher Plants

Cummins

2021

Front. Plant Sci.

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“…RuBISCO (a multi-meric photosynthetic enzyme), reflects potential for plant productivity and the efficiency of resource use by its net C assimilation rate. There is some substantial evidence in literature that described about H 2 S role of being a key regulator of plant photosynthetic apparatus ( Carmo-Silva et al, 2015 ; Cummins et al, 2018 ). In spinach, Chen et al (2011) found that NaHS-treated plants had significant increase in chlorophyll content alongside higher soluble protein content and biomass yield.…”

Section: Exogenous H 2 S Application: a Precursor mentioning

confidence: 99%

Role of Exogenous and Endogenous Hydrogen Sulfide (H2S) on Functional Traits of Plants Under Heavy Metal Stresses: A Recent Perspective

et al. 2021

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Improving growth and productivity of plants that are vulnerable to environmental stresses, such as heavy metals, is of significant importance for meeting global food and energy demands. Because heavy metal toxicity not only causes impaired plant growth, it has also posed many concerns related to human well-being, so mitigation of heavy metal pollution is a necessary priority for a cleaner environment and healthier world. Hydrogen sulfide (H2S), a gaseous signaling molecule, is involved in metal-related oxidative stress mitigation and increased stress tolerance in plants. It performs multifunctional roles in plant growth regulation while reducing the adverse effects of abiotic stress. Most effective function of H2S in plants is to eliminate metal-related oxidative toxicity by regulating several key physiobiochemical processes. Soil pollution by heavy metals presents significant environmental challenge due to the absence of vegetation cover and the resulting depletion of key soil functions. However, the use of stress alleviators, such as H2S, along with suitable crop plants, has considerable potential for an effective management of these contaminated soils. Overall, the present review examines the imperative role of exogenous application of different H2S donors in reducing HMs toxicity, by promoting plant growth, stabilizing their physiobiochemical processes, and upregulating antioxidative metabolic activities. In addition, crosstalk of different growth regulators with endogenous H2S and their contribution to the mitigation of metal phytotoxicity have also been explored.

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Genetic modification strategies for enhancing plant resilience to abiotic stresses in the context of climate change

KhokharVoytas,

Shahbaz,

Maqsood

et al. 2023

Funct Integr Genomics

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Response: Commentary: Directions for Optimization of Photosynthetic Carbon Fixation: RuBisCO’s Efficiency May Not Be So Constrained After All

Cited by 10 publications

References 23 publications

The Coevolution of RuBisCO, Photorespiration, and Carbon Concentrating Mechanisms in Higher Plants

The Coevolution of RuBisCO, Photorespiration, and Carbon Concentrating Mechanisms in Higher Plants

Role of Exogenous and Endogenous Hydrogen Sulfide (H2S) on Functional Traits of Plants Under Heavy Metal Stresses: A Recent Perspective

Genetic modification strategies for enhancing plant resilience to abiotic stresses in the context of climate change

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