Christine Raines - Academia.edu (original) (raw)
Papers by Christine Raines
![Research paper thumbnail of Feeding the world: impacts of elevated [CO2] on nutrient content of greenhouse grown fruit crops and options for future yield gains](https://attachments.academia-assets.com/111208476/thumbnails/1.jpg)
](Horticulture research, Feb 21, 2023
Several long-term studies have provided strong support demonstrating that growing crops under ele... more Several long-term studies have provided strong support demonstrating that growing crops under elevated [CO 2 ] can increase photosynthesis and result in an increase in yield, flavour and nutritional content (including but not limited to Vitamins C, E and pro-vitamin A). In the case of tomato, increases in yield by as much as 80 % are observed when plants are cultivated at 1000ppm [CO 2 ], which is consistent with current commercial greenhouse production methods in the tomato fruit industry. These results provide a clear demonstration of the potential for elevating [CO 2 ] for improving yield and quality in greenhouse crops. The major focus of this review is to bring together 50 years of observations evaluating the impact of elevated [CO 2 ] on fruit yield and fruit nutritional quality. In the final section, we consider the need to engineer improvements to photosynthesis and nitrogen assimilation to allow plants to take greater advantage of elevated CO 2 growth conditions.
To meet the growing demand for food, substantial improvements in yields are needed. This is parti... more To meet the growing demand for food, substantial improvements in yields are needed. This is particularly the case for wheat, where global yield has stagnated in recent years. Increasing photosynthesis has been identified as a primary target to achieve yield improvements. To increase leaf photosynthesis in wheat, the level of the Calvin–Benson cycle enzyme sedoheptulose-1,7-biphosphatase (SBPase) has been increased through transformation and expression of a Brachypodium distachyon SBPase gene construct. Transgenic lines with increased SBPase protein levels and activity were grown under greenhouse conditions and showed enhanced leaf photosynthesis and increased total biomass and dry seed yield. This showed the potential of improving yield potential by increasing leaf photosynthesis in a crop species such as wheat. The results are discussed with regards to future strategies for further improvement of photosynthesis in wheat.This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.
Philosophical Transactions of the Royal Society B, Aug 14, 2017
One contribution of 16 to a discussion meeting issue 'Enhancing photosynthesis in crop plants: ta... more One contribution of 16 to a discussion meeting issue 'Enhancing photosynthesis in crop plants: targets for improvement'.
Journal of Experimental Botany, Apr 28, 2015
Photosynthesis is one of the most important biochemical processes, underlying almost all life. It... more Photosynthesis is one of the most important biochemical processes, underlying almost all life. It is also one of the most vulnerable to environmental stress. Irradiance changes over the diurnal cycle is broadly predictable but, superimposed on that cycle, changes in cloud cover can cause order-of-magnitude variations in irradiance from second to second. The extent of cloud cover will change with the season and, depending on the shorter term weather patterns, giving periods of days to weeks of higher or lower irradiance. For example, the low crop yields in the UK in 2012 have been attributed to low levels of sunshine during the summer of that year. Rapid changes in irradiance can also arise due to sunflecks caused by the movement of leaves and the position of the sun relative to gaps in the canopy. Variation in shading will also affect the spectral quality of absorbed light. Changes in light absorption will have direct effects on the ability of plants to generate ATP and NADPH. At the same time, changes in temperature will affect the ability of plants to use those products of electron transport. The lowering of temperatures will result in a lowering of the rate of enzyme-catalysed reactions. At higher temperatures, changes in the solubility of CO 2 and O 2 and in the specificity of Rubisco will alter the extent of photorespiration. Temperatures fluctuate diurnally, but also depend on weather patterns over days to months. Fluctuations in water supply, even over short time periods, can lead to variation in stomatal conductance causing the CO 2 supply to fluctuate. All of the above factors can lead to imbalances between light capture and light use by the photosynthetic apparatus. When light absorption exceeds the capacity for the energy to be fixed, damage is likely to occur, either directly to the photosynthetic apparatus (especially Photosystem II) or more widespread damage caused by the generation of reactive oxygen species, such as singlet oxygen, superoxide, and hydrogen peroxide. In view of this, it might be thought that plants are in constant danger of bleaching themselves to death. The fact that this does not occur, that most plants are able to tolerate and even thrive in a wide range of continually fluctuating environments, is explained by an array of regulatory mechanisms that optimize the photosynthetic apparatus to the conditions experienced. These mechanisms operate on timescales ranging from minutes to weeks, with rapid responses involving the regulation of metabolic processes being followed by reengineering of metabolism through changing gene expression and protein concentrations. Most work in plant biology focuses on plants at a steady state. At the 2014 Annual Meeting of the Society of Experimental Biology, there was a session specifically focusing on how plants respond to fluctuations in the environment, in particular, in relation to the effects of dynamic conditions on photosynthesis. Papers included in this focus section present an excellent overview of the state of research in this emerging field, with a range of different approaches being covered. Schöttler et al. focus on how different environments alter the composition of the thylakoid membrane, describing work in particular that uses spectroscopic approaches to understand the importance of different responses. The review by Dietz looks at work using a systems biology approach in order to understand the early events in the response of plants to changes in light, examining sensing and signalling pathways. Kaiser et al. examine functional responses to fluctuations while Allahverdiyeva et al. look at processes involved in preventing damage to the photosynthetic apparatus during stress. In addition, the review by Retake et al. adopt a modelling approach to understand what the optimal solution is for plants to acclimate photosynthesis to different fluctuating conditions. Together, these papers provide a good cross-section of the range of different experimental approaches being adopted to understand how plants can improve their photosynthetic performance in natural environments. If we are to increase crop yields to meet growing demands, improving performance under natural conditions will be an essential step, which current strategies are poor at targeting. Defining the important types of fluctuation that affect plant productivity and identifying strategies that allow plants to cope with those will be an important step in meeting productivity goals.
In this study we have generated transgenic Arabidopsis plants over-expressing the Rieske FeS prot... more In this study we have generated transgenic Arabidopsis plants over-expressing the Rieske FeS protein (PetC), a component of the cytochrome b 6 f (cyt b 6 f) complex. Increasing the levels of this protein, resulted in the concomitant increase in the levels of cyt f (PetA) and cyt b 6 (PetB), core proteins of the cyt b 6 f complex. Interestingly, an increase in the levels of proteins in both the PSI and PSII complexes was also seen in the Rieske FeS ox plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, the overexpression of the Rieske FeS protein resulted in a substantial and significant impact on the quantum efficiency of PSI and PSII, electron transport, biomass and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity.
Journal of Experimental Botany, Apr 1, 2017
CP12 is a small, redox-sensitive protein, the most detailed understanding of which is the thiored... more CP12 is a small, redox-sensitive protein, the most detailed understanding of which is the thioredoxin-mediated regulation of the Calvin-Benson cycle, where it facilitates the formation of a complex between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) in response to changes in light intensity. In most organisms, CP12 proteins are encoded by small multigene families, where the importance of each individual CP12 gene in vivo has not yet been reported. We used Arabidopsis thaliana T-DNA mutants and RNAi transgenic lines with reduced levels of CP12 transcript to determine the relative importance of each of the CP12 genes. We found that single cp12-1, cp12-2, and cp12-3 mutants do not develop a severe photosynthetic or growth phenotype. In contrast, reductions of both CP12-1 and CP12-2 transcripts lead to reductions in photosynthetic capacity and to slower growth and reduced seed yield. No clear phenotype for CP12-3 was evident. Additionally, the levels of PRK protein are reduced in the cp12-1, cp12-1/2, and multiple mutants. Our results suggest that there is functional redundancy between CP12-1 and CP12-2 in Arabidopsis where these proteins have a role in determining the level of PRK in mature leaves and hence photosynthetic capacity.
Plant Physiology
Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle... more Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle, and increasing the abundance of SBPase in C3 plants provides higher photosynthetic rates and stimulates biomass and yield. C4 plants usually have higher photosynthetic rates because they operate a biochemical CO2-concentrating mechanism between mesophyll and bundle sheath cells. In the C4 system, SBPase and other enzymes of the Calvin cycle are localized to the bundle sheath cells. Here we tested what effect increasing abundance of SBPase would have on C4 photosynthesis. Using green foxtail millet (Setaria viridis), a model C4 plant of NADP-ME subtype, we created transgenic plants with 1.5 to 3.2 times higher SBPase content compared to wild-type plants. Transcripts of the transgene were found predominantly in the bundle sheaths suggesting the correct cellular localization of the protein. The abundance of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit was not affected in ...
Photosynthesis is fundamental for plant growth and yield. The Cytochrome b6f complex catalyses a ... more Photosynthesis is fundamental for plant growth and yield. The Cytochrome b6f complex catalyses a rate-limiting step in thylakoid electron transport and therefore represents an important point of regulation of photosynthesis. Here we show that overexpression of a single core subunit of Cytochrome b6f, the Rieske FeS protein, led to up to a 40% increase in the abundance of the complex in Nicotiana tabacum (tobacco) and was accompanied by an enhanced in vitro Cytochrome f activity, indicating a full functionality of the complex. Analysis of transgenic plants overexpressing Rieske FeS by the light-induced fluorescence transients technique revealed a more oxidised primary quinone acceptor of Photosystem II (QA) and plastoquinone pool and a faster electron transport from the plastoquinone pool to Photosystem I upon changes in irradiance, compared to control plants. A faster establishing of qE, the energy-dependent component of non-photochemical quenching, in transgenic plants suggested a ...
Journal of Experimental Botany
In this study, four tobacco transformants overexpressing the inorganic carbon transporter B gene ... more In this study, four tobacco transformants overexpressing the inorganic carbon transporter B gene (ictB) were screened for photosynthetic performance relative to the wild type (WT) in field-based conditions. The WT and transgenic tobacco plants were evaluated for photosynthetic performance to determine the maximum rate of carboxylation (Vc, max), maximum rate of electron transport (Jmax), the photosynthetic compensation point (Γ*), quantum yield of PSII (ΦPSII), and mesophyll conductance (gm). Additionally, all plants were harvested to compare differences in above-ground biomass. Overall, transformants did not perform better than the WT on photosynthesis-, biomass-, and leaf composition-related traits. This is in contrast to previous studies that have suggested significant increases in photosynthesis and yield with the overexpression of ictB, although not widely evaluated under field conditions. These findings suggest that the benefit of ictB is not universal and may only be seen und...
Frontiers in Plant Science, 2020
C 4 photosynthesis is characterized by the compartmentalization of the processes of atmospheric u... more C 4 photosynthesis is characterized by the compartmentalization of the processes of atmospheric uptake of CO 2 and its conversion into carbohydrate between mesophyll and bundle-sheath cells. As a result, most of the enzymes participating in the Calvin-Benson-Bassham (CBB) cycle, including RubisCO, are highly expressed in bundlesheath cells. There is evidence that changes in the regulatory sequences of RubisCO contribute to its bundle-sheath-specific expression, however, little is known about how the spatial-expression pattern of other CBB cycle enzymes is regulated. In this study, we use a computational approach to scan for transcription factor binding sites in the regulatory regions of the genes encoding CBB cycle enzymes, SBPase, FBPase, PRK, and GAPDH-B, of C 3 and C 4 grasses. We identified potential cis-regulatory elements present in each of the genes studied here, regardless of the photosynthetic path used by the plant. The transacting factors that bind these elements have been validated in A. thaliana and might regulate the expression of the genes encoding CBB cycle enzymes. In addition, we also found C 4-specific transcription factor binding sites in the genes encoding CBB cycle enzymes that could potentially contribute to the pathwayspecific regulation of gene expression. These results provide a foundation for the functional analysis of the differences in regulation of genes encoding CBB cycle enzymes between C 3 and C 4 grasses.
Previous studies have demonstrated that independent stimulation of either electron transport or R... more Previous studies have demonstrated that independent stimulation of either electron transport or RuBP regeneration can increase the rate of photosynthetic carbon assimilation and plant biomass. In this paper, we present evidence that a multi-gene approach to simultaneously manipulate these two processes provides a further stimulation of photosynthesis. We report on the introduction of the cyanobacterial bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase or overexpression of the plant enzyme sedoheptulose-1,7-bisphosphatase, together with expression of the red algal protein cytochromec6, and show that a further increase in biomass accumulation under both glasshouse and field conditions can be achieved. Furthermore, we provide evidence that the simultaneous stimulation of electron transport and RuBP regeneration can lead to enhanced intrinsic water use efficiency under field conditions.One sentence summarySimultaneous stimulation of RuBP regeneration and e...
Food and Energy Security, 2018
Ensuring food security in a changing climate is a major contemporary challenge and requires devel... more Ensuring food security in a changing climate is a major contemporary challenge and requires development of climate‐resilient crops that perform well under variable environments. The hypothesis that yield stability in suboptimal conditions is linked to yield penalties in optimal conditions was investigated in field‐grown wheat in the UK. The phenotypic responses, rate of wheat crop development, and final grain yield to varying sowing date, rainfall, air temperature, and radiation patterns were studied for a panel of 61 elite commercial wheat cultivars grown in the UK in 2012, 2013, and 2014. Contrasting climatic patterns, particularly rainfall accumulation and distribution over the season, influenced the relative performance of the cultivars affecting the duration of grain development stage and impacting on productivity. Indices for crop productivity, yield stability, and performance under suboptimal conditions revealed four cultivars with a combination of stable and high relative gr...
Plant Biotechnology Journal, 2018
SummaryPhotorespiration is essential for C3 plants, enabling oxygenic photosynthesis through the ... more SummaryPhotorespiration is essential for C3 plants, enabling oxygenic photosynthesis through the scavenging of 2‐phosphoglycolate. Previous studies have demonstrated that overexpression of the L‐ and H‐proteins of the photorespiratory glycine cleavage system results in an increase in photosynthesis and growth in Arabidopsis thaliana. Here, we present evidence that under controlled environment conditions an increase in biomass is evident in tobacco plants overexpressing the H‐protein. Importantly, the work in this paper provides a clear demonstration of the potential of this manipulation in tobacco grown in field conditions, in two separate seasons. We also demonstrate the importance of targeted overexpression of the H‐protein using the leaf‐specific promoter ST‐LS1. Although increases in the H‐protein driven by this promoter have a positive impact on biomass, higher levels of overexpression of this protein driven by the constitutive CaMV 35S promoter result in a reduction in the gro...
Journal of Integrative Plant Biology, 2018
In C3 plants, photorespiration is an energy‐expensive process, including the oxygenation of ribul... more In C3 plants, photorespiration is an energy‐expensive process, including the oxygenation of ribulose‐1,5‐bisphosphate (RuBP) by ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) and the ensuing multi‐organellar photorespiratory pathway required to recycle the toxic byproducts and recapture a portion of the fixed carbon. Photorespiration significantly impacts crop productivity through reducing yields in C3 crops by as much as 50% under severe conditions. Thus, reducing the flux through, or improving the efficiency of photorespiration has the potential of large improvements in C3 crop productivity. Here, we review an array of approaches intended to engineer photorespiration in a range of plant systems with the goal of increasing crop productivity. Approaches include optimizing flux through the native photorespiratory pathway, installing non‐native alternative photorespiratory pathways, and lowering or even eliminating Rubisco‐catalyzed oxygenation of RuBP to reduce substrate e...
Plant Biotechnology Journal, 2017
SummaryIn this article, we have altered the levels of three different enzymes involved in the Cal... more SummaryIn this article, we have altered the levels of three different enzymes involved in the Calvin–Benson cycle and photorespiratory pathway. We have generated transgenic Arabidopsis plants with altered combinations of sedoheptulose 1,7‐bisphosphatase (SBPase), fructose 1,6‐bisphophate aldolase (FBPA) and the glycine decarboxylase‐H protein (GDC‐H) gene identified as targets to improve photosynthesis based on previous studies. Here, we show that increasing the levels of the three corresponding proteins, either independently or in combination, significantly increases the quantum efficiency of PSII. Furthermore, photosynthetic measurements demonstrated an increase in the maximum efficiency of CO2 fixation in lines over‐expressing SBPase and FBPA. Moreover, the co‐expression of GDC‐H with SBPase and FBPA resulted in a cumulative positive impact on leaf area and biomass. Finally, further analysis of transgenic lines revealed a cumulative increase of seed yield in SFH lines grown in hi...
Plant physiology, Jan 9, 2017
Acclimation of plants to light has been studied extensively, yet little is known about the effect... more Acclimation of plants to light has been studied extensively, yet little is known about the effect of dynamic fluctuations in light on plant phenotype and acclimatory responses. We mimicked natural fluctuations in light over a diurnal period to examine the effect on photosynthetic processes and growth of Arabidopsis thaliana. High and low light intensities, delivered via a realistic dynamic fluctuating or square wave pattern were used to grow and assess plants. Plants subjected to square wave light had thicker leaves and greater photosynthetic capacity compared with fluctuating light grown plants. This together with elevated levels of proteins associated with electron transport indicates greater investment in leaf structural components and photosynthetic processes. In contrast plants grown under fluctuating light had thinner leaves, lower leaf light absorption but maintained similar photosynthetic rates per unit leaf area to square wave grown plants. Despite high light use efficiency...
Plant Physiology, Jul 28, 2017
In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing t... more In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the Rieske FeS protein (PetC), a component of the cytochrome b 6 f (cyt b 6 f) complex. Increasing the levels of this protein resulted in concomitant increases in the levels of cyt f (PetA) and cyt b 6 (PetB), core proteins of the cyt b 6 f complex. Interestingly, an increase in the levels of proteins in both the photosystem I (PSI) and PSII complexes also was seen in the Rieske FeS overexpression plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, overexpression of the Rieske FeS protein resulted in substantial and significant impacts on the quantum efficiency of PSI and PSII, electron transport, biomass, and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity.
Annual Plant Reviews online
The non-photosyntetic alga Euglena longa harbours a cryptic plastid of unknown function. By a com... more The non-photosyntetic alga Euglena longa harbours a cryptic plastid of unknown function. By a combination of bioinformatic and biochemical approaches we found out that this organelle houses a surprising set of metabolic processes. Biosynthesis of isoprenoid precursors and fatty acids is absent and the tetrapyrrole pathway is incomplete, whereas phospholipids and glycolipids are still being produced in the E. longa plastid. Unprecedented among non-photosynthetic plastids is the ability of this organelle to make tocopherols and a phylloquinone derivative. The most striking attribute is the presence of a linearized Calvin-Benson (CB) pathway including RuBisCO, together with ferredoxin-NADP + reductase and the ferredoxin/thioredoxin system. We hypothesize that the linear CB pathway is regulated by the redox status of the E. longa cell, in effect functioning as a redox valve bypassing the glycolytic oxidation of glyceraldehyde-3-phosphate to 3-phosphoglycerate. Altogether, the E. longa plastid defines a new class of relic plastids.
The abstracts herein are of presentations by crop experts for the ”3rd International Workshop of ... more The abstracts herein are of presentations by crop experts for the ”3rd International Workshop of the Wheat Yield Consortium”. Sponsored by SAGARPA’s international strategic component for increasing wheat performance, under the Sustainable Modernization of Traditional Agriculture Program (MasAgro); and GRDC, Australia. The event covers innovative methods to significantly raise wheat yield potential, including making photosynthesis more efficient, improving adaptation of flowering to diverse environments, addressing the physical processes involved in lodging, and physiological and molecular breeding. The workshop represents the current research of the International Wheat Yield Consortium that involves scientists working on all continents to strategically integrate research components in a common breeding platform, thereby speeding the delivery to farmers of new wheat genotypes. Thanks to Laura Martinez for her help in organizing the workshop and coordinating logistics, with the able a...
Journal of Experimental Botany, 2018
Horticulture research, Feb 21, 2023
Several long-term studies have provided strong support demonstrating that growing crops under ele... more Several long-term studies have provided strong support demonstrating that growing crops under elevated [CO 2 ] can increase photosynthesis and result in an increase in yield, flavour and nutritional content (including but not limited to Vitamins C, E and pro-vitamin A). In the case of tomato, increases in yield by as much as 80 % are observed when plants are cultivated at 1000ppm [CO 2 ], which is consistent with current commercial greenhouse production methods in the tomato fruit industry. These results provide a clear demonstration of the potential for elevating [CO 2 ] for improving yield and quality in greenhouse crops. The major focus of this review is to bring together 50 years of observations evaluating the impact of elevated [CO 2 ] on fruit yield and fruit nutritional quality. In the final section, we consider the need to engineer improvements to photosynthesis and nitrogen assimilation to allow plants to take greater advantage of elevated CO 2 growth conditions.
To meet the growing demand for food, substantial improvements in yields are needed. This is parti... more To meet the growing demand for food, substantial improvements in yields are needed. This is particularly the case for wheat, where global yield has stagnated in recent years. Increasing photosynthesis has been identified as a primary target to achieve yield improvements. To increase leaf photosynthesis in wheat, the level of the Calvin–Benson cycle enzyme sedoheptulose-1,7-biphosphatase (SBPase) has been increased through transformation and expression of a Brachypodium distachyon SBPase gene construct. Transgenic lines with increased SBPase protein levels and activity were grown under greenhouse conditions and showed enhanced leaf photosynthesis and increased total biomass and dry seed yield. This showed the potential of improving yield potential by increasing leaf photosynthesis in a crop species such as wheat. The results are discussed with regards to future strategies for further improvement of photosynthesis in wheat.This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.
Philosophical Transactions of the Royal Society B, Aug 14, 2017
One contribution of 16 to a discussion meeting issue 'Enhancing photosynthesis in crop plants: ta... more One contribution of 16 to a discussion meeting issue 'Enhancing photosynthesis in crop plants: targets for improvement'.
Journal of Experimental Botany, Apr 28, 2015
Photosynthesis is one of the most important biochemical processes, underlying almost all life. It... more Photosynthesis is one of the most important biochemical processes, underlying almost all life. It is also one of the most vulnerable to environmental stress. Irradiance changes over the diurnal cycle is broadly predictable but, superimposed on that cycle, changes in cloud cover can cause order-of-magnitude variations in irradiance from second to second. The extent of cloud cover will change with the season and, depending on the shorter term weather patterns, giving periods of days to weeks of higher or lower irradiance. For example, the low crop yields in the UK in 2012 have been attributed to low levels of sunshine during the summer of that year. Rapid changes in irradiance can also arise due to sunflecks caused by the movement of leaves and the position of the sun relative to gaps in the canopy. Variation in shading will also affect the spectral quality of absorbed light. Changes in light absorption will have direct effects on the ability of plants to generate ATP and NADPH. At the same time, changes in temperature will affect the ability of plants to use those products of electron transport. The lowering of temperatures will result in a lowering of the rate of enzyme-catalysed reactions. At higher temperatures, changes in the solubility of CO 2 and O 2 and in the specificity of Rubisco will alter the extent of photorespiration. Temperatures fluctuate diurnally, but also depend on weather patterns over days to months. Fluctuations in water supply, even over short time periods, can lead to variation in stomatal conductance causing the CO 2 supply to fluctuate. All of the above factors can lead to imbalances between light capture and light use by the photosynthetic apparatus. When light absorption exceeds the capacity for the energy to be fixed, damage is likely to occur, either directly to the photosynthetic apparatus (especially Photosystem II) or more widespread damage caused by the generation of reactive oxygen species, such as singlet oxygen, superoxide, and hydrogen peroxide. In view of this, it might be thought that plants are in constant danger of bleaching themselves to death. The fact that this does not occur, that most plants are able to tolerate and even thrive in a wide range of continually fluctuating environments, is explained by an array of regulatory mechanisms that optimize the photosynthetic apparatus to the conditions experienced. These mechanisms operate on timescales ranging from minutes to weeks, with rapid responses involving the regulation of metabolic processes being followed by reengineering of metabolism through changing gene expression and protein concentrations. Most work in plant biology focuses on plants at a steady state. At the 2014 Annual Meeting of the Society of Experimental Biology, there was a session specifically focusing on how plants respond to fluctuations in the environment, in particular, in relation to the effects of dynamic conditions on photosynthesis. Papers included in this focus section present an excellent overview of the state of research in this emerging field, with a range of different approaches being covered. Schöttler et al. focus on how different environments alter the composition of the thylakoid membrane, describing work in particular that uses spectroscopic approaches to understand the importance of different responses. The review by Dietz looks at work using a systems biology approach in order to understand the early events in the response of plants to changes in light, examining sensing and signalling pathways. Kaiser et al. examine functional responses to fluctuations while Allahverdiyeva et al. look at processes involved in preventing damage to the photosynthetic apparatus during stress. In addition, the review by Retake et al. adopt a modelling approach to understand what the optimal solution is for plants to acclimate photosynthesis to different fluctuating conditions. Together, these papers provide a good cross-section of the range of different experimental approaches being adopted to understand how plants can improve their photosynthetic performance in natural environments. If we are to increase crop yields to meet growing demands, improving performance under natural conditions will be an essential step, which current strategies are poor at targeting. Defining the important types of fluctuation that affect plant productivity and identifying strategies that allow plants to cope with those will be an important step in meeting productivity goals.
In this study we have generated transgenic Arabidopsis plants over-expressing the Rieske FeS prot... more In this study we have generated transgenic Arabidopsis plants over-expressing the Rieske FeS protein (PetC), a component of the cytochrome b 6 f (cyt b 6 f) complex. Increasing the levels of this protein, resulted in the concomitant increase in the levels of cyt f (PetA) and cyt b 6 (PetB), core proteins of the cyt b 6 f complex. Interestingly, an increase in the levels of proteins in both the PSI and PSII complexes was also seen in the Rieske FeS ox plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, the overexpression of the Rieske FeS protein resulted in a substantial and significant impact on the quantum efficiency of PSI and PSII, electron transport, biomass and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity.
Journal of Experimental Botany, Apr 1, 2017
CP12 is a small, redox-sensitive protein, the most detailed understanding of which is the thiored... more CP12 is a small, redox-sensitive protein, the most detailed understanding of which is the thioredoxin-mediated regulation of the Calvin-Benson cycle, where it facilitates the formation of a complex between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) in response to changes in light intensity. In most organisms, CP12 proteins are encoded by small multigene families, where the importance of each individual CP12 gene in vivo has not yet been reported. We used Arabidopsis thaliana T-DNA mutants and RNAi transgenic lines with reduced levels of CP12 transcript to determine the relative importance of each of the CP12 genes. We found that single cp12-1, cp12-2, and cp12-3 mutants do not develop a severe photosynthetic or growth phenotype. In contrast, reductions of both CP12-1 and CP12-2 transcripts lead to reductions in photosynthetic capacity and to slower growth and reduced seed yield. No clear phenotype for CP12-3 was evident. Additionally, the levels of PRK protein are reduced in the cp12-1, cp12-1/2, and multiple mutants. Our results suggest that there is functional redundancy between CP12-1 and CP12-2 in Arabidopsis where these proteins have a role in determining the level of PRK in mature leaves and hence photosynthetic capacity.
Plant Physiology
Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle... more Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle, and increasing the abundance of SBPase in C3 plants provides higher photosynthetic rates and stimulates biomass and yield. C4 plants usually have higher photosynthetic rates because they operate a biochemical CO2-concentrating mechanism between mesophyll and bundle sheath cells. In the C4 system, SBPase and other enzymes of the Calvin cycle are localized to the bundle sheath cells. Here we tested what effect increasing abundance of SBPase would have on C4 photosynthesis. Using green foxtail millet (Setaria viridis), a model C4 plant of NADP-ME subtype, we created transgenic plants with 1.5 to 3.2 times higher SBPase content compared to wild-type plants. Transcripts of the transgene were found predominantly in the bundle sheaths suggesting the correct cellular localization of the protein. The abundance of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit was not affected in ...
Photosynthesis is fundamental for plant growth and yield. The Cytochrome b6f complex catalyses a ... more Photosynthesis is fundamental for plant growth and yield. The Cytochrome b6f complex catalyses a rate-limiting step in thylakoid electron transport and therefore represents an important point of regulation of photosynthesis. Here we show that overexpression of a single core subunit of Cytochrome b6f, the Rieske FeS protein, led to up to a 40% increase in the abundance of the complex in Nicotiana tabacum (tobacco) and was accompanied by an enhanced in vitro Cytochrome f activity, indicating a full functionality of the complex. Analysis of transgenic plants overexpressing Rieske FeS by the light-induced fluorescence transients technique revealed a more oxidised primary quinone acceptor of Photosystem II (QA) and plastoquinone pool and a faster electron transport from the plastoquinone pool to Photosystem I upon changes in irradiance, compared to control plants. A faster establishing of qE, the energy-dependent component of non-photochemical quenching, in transgenic plants suggested a ...
Journal of Experimental Botany
In this study, four tobacco transformants overexpressing the inorganic carbon transporter B gene ... more In this study, four tobacco transformants overexpressing the inorganic carbon transporter B gene (ictB) were screened for photosynthetic performance relative to the wild type (WT) in field-based conditions. The WT and transgenic tobacco plants were evaluated for photosynthetic performance to determine the maximum rate of carboxylation (Vc, max), maximum rate of electron transport (Jmax), the photosynthetic compensation point (Γ*), quantum yield of PSII (ΦPSII), and mesophyll conductance (gm). Additionally, all plants were harvested to compare differences in above-ground biomass. Overall, transformants did not perform better than the WT on photosynthesis-, biomass-, and leaf composition-related traits. This is in contrast to previous studies that have suggested significant increases in photosynthesis and yield with the overexpression of ictB, although not widely evaluated under field conditions. These findings suggest that the benefit of ictB is not universal and may only be seen und...
Frontiers in Plant Science, 2020
C 4 photosynthesis is characterized by the compartmentalization of the processes of atmospheric u... more C 4 photosynthesis is characterized by the compartmentalization of the processes of atmospheric uptake of CO 2 and its conversion into carbohydrate between mesophyll and bundle-sheath cells. As a result, most of the enzymes participating in the Calvin-Benson-Bassham (CBB) cycle, including RubisCO, are highly expressed in bundlesheath cells. There is evidence that changes in the regulatory sequences of RubisCO contribute to its bundle-sheath-specific expression, however, little is known about how the spatial-expression pattern of other CBB cycle enzymes is regulated. In this study, we use a computational approach to scan for transcription factor binding sites in the regulatory regions of the genes encoding CBB cycle enzymes, SBPase, FBPase, PRK, and GAPDH-B, of C 3 and C 4 grasses. We identified potential cis-regulatory elements present in each of the genes studied here, regardless of the photosynthetic path used by the plant. The transacting factors that bind these elements have been validated in A. thaliana and might regulate the expression of the genes encoding CBB cycle enzymes. In addition, we also found C 4-specific transcription factor binding sites in the genes encoding CBB cycle enzymes that could potentially contribute to the pathwayspecific regulation of gene expression. These results provide a foundation for the functional analysis of the differences in regulation of genes encoding CBB cycle enzymes between C 3 and C 4 grasses.
Previous studies have demonstrated that independent stimulation of either electron transport or R... more Previous studies have demonstrated that independent stimulation of either electron transport or RuBP regeneration can increase the rate of photosynthetic carbon assimilation and plant biomass. In this paper, we present evidence that a multi-gene approach to simultaneously manipulate these two processes provides a further stimulation of photosynthesis. We report on the introduction of the cyanobacterial bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase or overexpression of the plant enzyme sedoheptulose-1,7-bisphosphatase, together with expression of the red algal protein cytochromec6, and show that a further increase in biomass accumulation under both glasshouse and field conditions can be achieved. Furthermore, we provide evidence that the simultaneous stimulation of electron transport and RuBP regeneration can lead to enhanced intrinsic water use efficiency under field conditions.One sentence summarySimultaneous stimulation of RuBP regeneration and e...
Food and Energy Security, 2018
Ensuring food security in a changing climate is a major contemporary challenge and requires devel... more Ensuring food security in a changing climate is a major contemporary challenge and requires development of climate‐resilient crops that perform well under variable environments. The hypothesis that yield stability in suboptimal conditions is linked to yield penalties in optimal conditions was investigated in field‐grown wheat in the UK. The phenotypic responses, rate of wheat crop development, and final grain yield to varying sowing date, rainfall, air temperature, and radiation patterns were studied for a panel of 61 elite commercial wheat cultivars grown in the UK in 2012, 2013, and 2014. Contrasting climatic patterns, particularly rainfall accumulation and distribution over the season, influenced the relative performance of the cultivars affecting the duration of grain development stage and impacting on productivity. Indices for crop productivity, yield stability, and performance under suboptimal conditions revealed four cultivars with a combination of stable and high relative gr...
Plant Biotechnology Journal, 2018
SummaryPhotorespiration is essential for C3 plants, enabling oxygenic photosynthesis through the ... more SummaryPhotorespiration is essential for C3 plants, enabling oxygenic photosynthesis through the scavenging of 2‐phosphoglycolate. Previous studies have demonstrated that overexpression of the L‐ and H‐proteins of the photorespiratory glycine cleavage system results in an increase in photosynthesis and growth in Arabidopsis thaliana. Here, we present evidence that under controlled environment conditions an increase in biomass is evident in tobacco plants overexpressing the H‐protein. Importantly, the work in this paper provides a clear demonstration of the potential of this manipulation in tobacco grown in field conditions, in two separate seasons. We also demonstrate the importance of targeted overexpression of the H‐protein using the leaf‐specific promoter ST‐LS1. Although increases in the H‐protein driven by this promoter have a positive impact on biomass, higher levels of overexpression of this protein driven by the constitutive CaMV 35S promoter result in a reduction in the gro...
Journal of Integrative Plant Biology, 2018
In C3 plants, photorespiration is an energy‐expensive process, including the oxygenation of ribul... more In C3 plants, photorespiration is an energy‐expensive process, including the oxygenation of ribulose‐1,5‐bisphosphate (RuBP) by ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) and the ensuing multi‐organellar photorespiratory pathway required to recycle the toxic byproducts and recapture a portion of the fixed carbon. Photorespiration significantly impacts crop productivity through reducing yields in C3 crops by as much as 50% under severe conditions. Thus, reducing the flux through, or improving the efficiency of photorespiration has the potential of large improvements in C3 crop productivity. Here, we review an array of approaches intended to engineer photorespiration in a range of plant systems with the goal of increasing crop productivity. Approaches include optimizing flux through the native photorespiratory pathway, installing non‐native alternative photorespiratory pathways, and lowering or even eliminating Rubisco‐catalyzed oxygenation of RuBP to reduce substrate e...
Plant Biotechnology Journal, 2017
SummaryIn this article, we have altered the levels of three different enzymes involved in the Cal... more SummaryIn this article, we have altered the levels of three different enzymes involved in the Calvin–Benson cycle and photorespiratory pathway. We have generated transgenic Arabidopsis plants with altered combinations of sedoheptulose 1,7‐bisphosphatase (SBPase), fructose 1,6‐bisphophate aldolase (FBPA) and the glycine decarboxylase‐H protein (GDC‐H) gene identified as targets to improve photosynthesis based on previous studies. Here, we show that increasing the levels of the three corresponding proteins, either independently or in combination, significantly increases the quantum efficiency of PSII. Furthermore, photosynthetic measurements demonstrated an increase in the maximum efficiency of CO2 fixation in lines over‐expressing SBPase and FBPA. Moreover, the co‐expression of GDC‐H with SBPase and FBPA resulted in a cumulative positive impact on leaf area and biomass. Finally, further analysis of transgenic lines revealed a cumulative increase of seed yield in SFH lines grown in hi...
Plant physiology, Jan 9, 2017
Acclimation of plants to light has been studied extensively, yet little is known about the effect... more Acclimation of plants to light has been studied extensively, yet little is known about the effect of dynamic fluctuations in light on plant phenotype and acclimatory responses. We mimicked natural fluctuations in light over a diurnal period to examine the effect on photosynthetic processes and growth of Arabidopsis thaliana. High and low light intensities, delivered via a realistic dynamic fluctuating or square wave pattern were used to grow and assess plants. Plants subjected to square wave light had thicker leaves and greater photosynthetic capacity compared with fluctuating light grown plants. This together with elevated levels of proteins associated with electron transport indicates greater investment in leaf structural components and photosynthetic processes. In contrast plants grown under fluctuating light had thinner leaves, lower leaf light absorption but maintained similar photosynthetic rates per unit leaf area to square wave grown plants. Despite high light use efficiency...
Plant Physiology, Jul 28, 2017
In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing t... more In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the Rieske FeS protein (PetC), a component of the cytochrome b 6 f (cyt b 6 f) complex. Increasing the levels of this protein resulted in concomitant increases in the levels of cyt f (PetA) and cyt b 6 (PetB), core proteins of the cyt b 6 f complex. Interestingly, an increase in the levels of proteins in both the photosystem I (PSI) and PSII complexes also was seen in the Rieske FeS overexpression plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, overexpression of the Rieske FeS protein resulted in substantial and significant impacts on the quantum efficiency of PSI and PSII, electron transport, biomass, and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity.
Annual Plant Reviews online
The non-photosyntetic alga Euglena longa harbours a cryptic plastid of unknown function. By a com... more The non-photosyntetic alga Euglena longa harbours a cryptic plastid of unknown function. By a combination of bioinformatic and biochemical approaches we found out that this organelle houses a surprising set of metabolic processes. Biosynthesis of isoprenoid precursors and fatty acids is absent and the tetrapyrrole pathway is incomplete, whereas phospholipids and glycolipids are still being produced in the E. longa plastid. Unprecedented among non-photosynthetic plastids is the ability of this organelle to make tocopherols and a phylloquinone derivative. The most striking attribute is the presence of a linearized Calvin-Benson (CB) pathway including RuBisCO, together with ferredoxin-NADP + reductase and the ferredoxin/thioredoxin system. We hypothesize that the linear CB pathway is regulated by the redox status of the E. longa cell, in effect functioning as a redox valve bypassing the glycolytic oxidation of glyceraldehyde-3-phosphate to 3-phosphoglycerate. Altogether, the E. longa plastid defines a new class of relic plastids.
The abstracts herein are of presentations by crop experts for the ”3rd International Workshop of ... more The abstracts herein are of presentations by crop experts for the ”3rd International Workshop of the Wheat Yield Consortium”. Sponsored by SAGARPA’s international strategic component for increasing wheat performance, under the Sustainable Modernization of Traditional Agriculture Program (MasAgro); and GRDC, Australia. The event covers innovative methods to significantly raise wheat yield potential, including making photosynthesis more efficient, improving adaptation of flowering to diverse environments, addressing the physical processes involved in lodging, and physiological and molecular breeding. The workshop represents the current research of the International Wheat Yield Consortium that involves scientists working on all continents to strategically integrate research components in a common breeding platform, thereby speeding the delivery to farmers of new wheat genotypes. Thanks to Laura Martinez for her help in organizing the workshop and coordinating logistics, with the able a...
Journal of Experimental Botany, 2018