Efficient Regulation of CO2 Assimilation Enables Greater Resilience to High Temperature and Drought in Maize

Increasing temperatures and extended drought episodes are among the major constraints affecting food production. Maize has a relatively high temperature optimum for photosynthesis compared to C3 crops, however, the response of this important C4 crop to the combination of heat and drought stress is poorly understood. Here, we hypothesized that resilience to high temperature combined with water deficit (WD) would require efficient regulation of the photosynthetic traits of maize, including the C4–CO2 concentrating mechanism (CCM). Two genotypes of maize with contrasting levels of drought and heat tolerance, B73 and P0023, were acclimatized at high temperature (38°C versus 25°C) under well-watered (WW) or WD conditions. The photosynthetic performance was evaluated by gas exchange and chlorophyll a fluorescence, and in vitro activities of key enzymes for carboxylation (phosphoenolpyruvate carboxylase), decarboxylation (NADP-malic enzyme), and carbon fixation (Rubisco). Both genotypes successfully acclimatized to the high temperature, although with different mechanisms: while B73 maintained the photosynthetic rates by increasing stomatal conductance (gs), P0023 maintained gs and showed limited transpiration. When WD was experienced in combination with high temperatures, limited transpiration allowed water-savings and acted as a drought stress avoidance mechanism. The photosynthetic efficiency in P0023 was sustained by higher phosphorylated PEPC and electron transport rate (ETR) near vascular tissues, supplying chemical energy for an effective CCM. These results suggest that the key traits for drought and heat tolerance in maize are limited transpiration rate, allied with a synchronized regulation of the carbon assimilation metabolism. These findings can be exploited in future breeding efforts aimed at improving maize resilience to climate change.

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Hybridization Assays in Strawberry Tree Towards the Identification of Plants Displaying Increased Drought Tolerance

10.20944/preprints202101.0164.v1 ◽

2021 ◽

Author(s):

João Martins ◽

Pedro Monteiro ◽

Glória Pinto ◽

Jorge Canhoto

Keyword(s):

Drought Stress ◽

Drought Tolerance ◽

Ecological Impact ◽

Tree Breeding ◽

Co2 Assimilation ◽

Fruit Production ◽

Plant Performance ◽

Water Restriction ◽

Strawberry Tree

Arbutus unedo L. is a small Ericaceae tree with a circum-Mediterranean distribution. It has a huge ecological impact on southern Europe forests and a great economic importance, as a source of phytochemicals with bioactive properties and for fruit production. On the foreseen climate change context, breeding towards drought tolerance is necessary in order to ameliorate plant performance. The aim of this work was therefore to study the reproduction mechanisms of strawberry tree, obtain new genetic combinations by hybridization and select genotypes more tolerant to drought stress. A morphological analysis of flowers and pollen was carried out, and controlled pollinations performed both in vitro and ex vitro. The very first approach on strawberry tree breeding by means of hybridization is also presented. Several physiological parameters were evaluated on 26 genotypes submitted to a water deficit regime. Plant behavior under drought greatly varied among genotypes, which showed a high phenotype plasticity. Three genotypes that were able to cope with water restriction without compromising net CO2 assimilation were identified as highly tolerant to drought stress. The results obtained elucidate the reproduction mechanisms of strawberry tree and open the way for a long-term breeding program based on the selection of drought tolerant plants.

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Photosynthesis and Growth of Pennisetum centrasiaticum (C4) is Superior to Calamagrostis pseudophragmites (C3) during Drought and Recovery

Plants ◽

10.3390/plants9080991 ◽

2020 ◽

Vol 9 (8) ◽

pp. 991

Author(s):

Yayong Luo ◽

Xueyong Zhao ◽

Ginger R. H. Allington ◽

Lilong Wang ◽

Wenda Huang ◽

...

Keyword(s):

Drought Stress ◽

Water Status ◽

Regional Climate ◽

Co2 Assimilation ◽

Photosynthetic Performance ◽

Thermal Dissipation ◽

Plant Responses ◽

C4 Plant ◽

C3 Plant ◽

Ecosystem Level

Global warming and changes in rainfall patterns may put many ecosystems at risk of drought. These stressors could be particularly destructive in arid systems where species are already water-limited. Understanding plant responses in terms of photosynthesis and growth to drought and rewatering is essential for predicting ecosystem-level responses to climate change. Different drought responses of C3 and C4 species could have important ecological implications affecting interspecific competition and distribution of plant communities in the future. For this study, C4 plant Pennisetum centrasiaticum and C3 plant Calamagrostis pseudophragmites were subjected to progressive drought and subsequent rewatering in order to better understand their differential responses to regional climate changes. We tracked responses in gas exchange, chlorophyll fluorescence, biomass as well as soil water status in order to investigate the ecophysiological responses of these two plant functional types. Similar patterns of photosynthetic regulations were observed during drought and rewatering for both psammophytes. They experienced stomatal restriction and nonstomatal restriction successively during drought. Photosynthetic performance recovered to the levels in well-watered plants after rewatering for 6–8 days. The C4 plant, P. centrasiaticum, exhibited the classic CO2-concentrating mechanism and more efficient thermal dissipation in the leaves, which confers more efficient CO2 assimilation and water use efficiency, alleviating drought stress, maintaining their photosynthetic advantage until water deficits became severe and quicker recovery after rewatering. In addition, P. centrasiaticum can allocate a greater proportion of root biomass in case of adequate water supply and a greater proportion of above-ground biomass in case of drought stress. This physiological adaptability and morphological adjustment underline the capacity of C4 plant P. centrasiaticum to withstand drought more efficiently and recover upon rewatering more quickly than C. pseudophragmites and dominate in the Horqin Sandy Land.

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Stomatal and photochemical limitations of photosynthesis in coffee (Coffea spp.) plants subjected to elevated temperatures

Crop and Pasture Science ◽

10.1071/cp17044 ◽

2018 ◽

Vol 69 (3) ◽

pp. 317 ◽

Cited By ~ 5

Author(s):

Weverton P. Rodrigues ◽

Jefferson R. Silva ◽

Luciene S. Ferreira ◽

José A. Machado Filho ◽

Fabio A. M. M. A. Figueiredo ◽

...

Keyword(s):

High Temperature ◽

Elevated Temperatures ◽

Stomatal Density ◽

Stomatal Closure ◽

Carbon Assimilation ◽

Field Capacity ◽

Photosynthetic Performance ◽

Potted Plants ◽

Intrinsic Water Use Efficiency ◽

Mild Temperature

Temperature increase assumes a prominent role in the context of expected climate change because of its significant impact on plant metabolism. High temperature can affect the carbon-assimilation pathway at both stomatal and non-stomatal levels, mainly through stomatal closure and photochemical and biochemical limitations. In general, however, plants have some ability to trigger acclimation mechanisms to cope with stressful conditions, especially if the limitations are imposed in a gradual manner during seasonal change. This study aims at evaluating changes at stomatal and photochemical levels in Coffea arabica and C. canephora under exposure to mild temperature (spring) and high temperature (summer). Potted plants were maintained in a greenhouse, watered to field capacity and subject to natural variations of light, temperature and relative humidity. In C. arabica, exposure to summer conditions decreased photosynthetic rates (A), stomatal conductance (gs) and stomatal density and increased intrinsic water-use efficiency (iWUE) compared with spring values, whereas C. canephora plants maintained similar values in both seasons. However, C. canephora presented lower A and gs during spring than C. arabica. Because photosynthetic capacity (Amax), photosynthetic performance index and membrane permeability were similar between genotypes and seasons, and maximum quantum yield (Fv/Fm) and photosynthetic pigments were not affected in C. arabica in summer, we conclude that under high temperature conditions, stomatal closure imposes the major limitation on C. arabica photosynthesis in summer. Finally, both coffee genotypes were able to avoid damage to photochemistry pathway under supra-optimal temperatures.

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The global mass and average rate of rubisco

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1816654116 ◽

2019 ◽

Vol 116 (10) ◽

pp. 4738-4743 ◽

Cited By ~ 34

Author(s):

Yinon M. Bar-On ◽

Ron Milo

Keyword(s):

Total Mass ◽

Carbon Fixation ◽

Average Rate ◽

Carbon Assimilation ◽

Dry Weight ◽

Effective Rate ◽

Terrestrial Plants ◽

Bisphosphate Carboxylase ◽

Catalytic Rate

Photosynthetic carbon assimilation enables energy storage in the living world and produces most of the biomass in the biosphere. Rubisco (d-ribulose 1,5-bisphosphate carboxylase/oxygenase) is responsible for the vast majority of global carbon fixation and has been claimed to be the most abundant protein on Earth. Here we provide an updated and rigorous estimate for the total mass of Rubisco on Earth, concluding it is ≈0.7 Gt, more than an order of magnitude higher than previously thought. We find that >90% of Rubisco enzymes are found in the ≈2 × 1014m2of leaves of terrestrial plants, and that Rubisco accounts for ≈3% of the total mass of leaves, which we estimate at ≈30 Gt dry weight. We use our estimate for the total mass of Rubisco to derive the effective time-averaged catalytic rate of Rubisco of ≈0.03 s−1on land and ≈0.6 s−1in the ocean. Compared with the maximal catalytic rate observed in vitro at 25 °C, the effective rate in the wild is ≈100-fold slower on land and sevenfold slower in the ocean. The lower ambient temperature, and Rubisco not working at night, can explain most of the difference from laboratory conditions in the ocean but not on land, where quantification of many more factors on a global scale is needed. Our analysis helps sharpen the dramatic difference between laboratory and wild environments and between the terrestrial and marine environments.

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Development of an in vitro Microtuberization and Temporary Immersion Bioreactor System to Evaluate Heat Stress Tolerance in Potatoes (Solanum tuberosum L.)

Frontiers in Plant Science ◽

10.3389/fpls.2021.700328 ◽

2021 ◽

Vol 12 ◽

Author(s):

Sanjeev Gautam ◽

Nora Solis-Gracia ◽

Megan K. Teale ◽

Kranthi Mandadi ◽

Jorge A. da Silva ◽

...

Keyword(s):

Heat Stress ◽

High Temperature ◽

Stress Tolerance ◽

Heat Tolerance ◽

Potato Variety ◽

Temporary Immersion Bioreactor ◽

Temporary Immersion ◽

Bioreactor System ◽

Heat Tolerant

High temperature (heat) stress reduces tuber yield and quality of potatoes. Screening potatoes for heat tolerance is increasingly important, considering the climate change scenario and expansion of potatoes to countries where heat stress is an issue. In vitro screening for tolerance to abiotic stresses offers several advantages, including quick evaluation of numerous genotypes (clones) in reduced space, controlled environmental conditions (temperature and photoperiod), and free from confounding variables inherent to greenhouse and field conditions. In this study, we explored the feasibility of using a temporary immersion bioreactor system for heat tolerance screening of potatoes. We determined the best hormone-free microtuberizing media for this system (MSG with 8% sucrose) to enhance microtuber number and size. Comparisons of microtubers produced at 30°C as heat treatment, with 16°C as normal condition, allowed to identify heat tolerant and susceptible potato clones. The use of bioreactors allowed distinguishing well-formed (non-deformed) from deformed microtubers. Heat stress increased the total biomass of plant tissues in all the clones. However, the effect of heat stress on microtuber number and weight varied among the clones. Incubation at 30°C decreased the weight and number of non-deformed microtubers in all the clones except for Reveille Russet in which the weight of non-deformed microtubers was significantly increased and the count of non-deformed microtubers was not affected. The potato variety Reveille Russet, which was selected under high-temperature field conditions in Texas, had many non-deformed microtubers per explant and the highest microtuber weight among four clones evaluated under heat stress. We described a faster and reliable in vitro microtuberization system for abiotic stress tolerance screening, identified Reveille Russet as a promising heat-tolerant potato variety, and confirmed Russet Burbank and Atlantic as susceptible heat-tolerant checks.

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Computational protein design enables a novel one-carbon assimilation pathway

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1500545112 ◽

2015 ◽

Vol 112 (12) ◽

pp. 3704-3709 ◽

Cited By ~ 141

Author(s):

Justin B. Siegel ◽

Amanda Lee Smith ◽

Sean Poust ◽

Adam J. Wargacki ◽

Arren Bar-Even ◽

...

Keyword(s):

Protein Design ◽

Biosynthetic Pathway ◽

Carbon Fixation ◽

Carbon Assimilation ◽

Dihydroxyacetone Phosphate ◽

Design Tools ◽

Chemical Transformations ◽

Central Metabolism ◽

Naturally Occurring

We describe a computationally designed enzyme, formolase (FLS), which catalyzes the carboligation of three one-carbon formaldehyde molecules into one three-carbon dihydroxyacetone molecule. The existence of FLS enables the design of a new carbon fixation pathway, the formolase pathway, consisting of a small number of thermodynamically favorable chemical transformations that convert formate into a three-carbon sugar in central metabolism. The formolase pathway is predicted to use carbon more efficiently and with less backward flux than any naturally occurring one-carbon assimilation pathway. When supplemented with enzymes carrying out the other steps in the pathway, FLS converts formate into dihydroxyacetone phosphate and other central metabolites in vitro. These results demonstrate how modern protein engineering and design tools can facilitate the construction of a completely new biosynthetic pathway.

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Hybridization Assays in Strawberry Tree toward the Identification of Plants Displaying Increased Drought Tolerance

Forests ◽

10.3390/f12020148 ◽

2021 ◽

Vol 12 (2) ◽

pp. 148

Author(s):

João Martins ◽

Pedro Monteiro ◽

Glória Pinto ◽

Jorge Canhoto

Keyword(s):

Drought Stress ◽

Drought Tolerance ◽

Ecological Impact ◽

Tree Breeding ◽

Co2 Assimilation ◽

Fruit Production ◽

Plant Performance ◽

Water Restriction ◽

Strawberry Tree

Arbutus unedo L. is a small Ericaceae tree with a circum-Mediterranean distribution. It has a huge ecological impact on southern Europe forests and a great economic importance as a source of phytochemicals with bioactive properties and for fruit production. On the foreseen climate change context, breeding toward drought tolerance is necessary in order to ameliorate plant performance. Therefore, the aim of this work was to study the reproduction mechanisms of the strawberry tree, obtain new genetic combinations by hybridization, and select genotypes more tolerant to drought stress. A morphological analysis of flowers and pollen was carried out, and controlled pollinations were performed both in vitro and ex vitro. The very first approach on strawberry tree breeding by means of hybridization is also presented. Several physiological parameters were evaluated on 26 genotypes submitted to a water-deficit regime. Plant behavior under drought greatly varied among genotypes, which showed high phenotype plasticity. Three genotypes that were able to cope with water restriction without compromising net CO2 assimilation were identified as highly tolerant to drought stress. The results obtained elucidate the reproduction mechanisms of the strawberry tree and open the way for a long-term breeding program based on the selection of drought-tolerant plants.

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Sectioned rubisco crystals in TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010016087x ◽

1990 ◽

Vol 48 (3) ◽

pp. 664-665

Author(s):

Gunnel Karlsson ◽

Jan-Olov Bovin ◽

Michael Bosma

Keyword(s):

Plant Cell ◽

Carbon Fixation ◽

Unit Cell ◽

Protein Crystals ◽

Unit Cell Parameters ◽

Cell Parameters ◽

Photosynthetic Carbon Fixation ◽

Photosynthetic Carbon

RuBisCO (D-ribulose-l,5-biphosphate carboxylase/oxygenase) is the most aboundant enzyme in the plant cell and it catalyses the key carboxylation reaction of photosynthetic carbon fixation, but also the competing oxygenase reaction of photorespiation. In vitro crystallized RuBisCO has been studied earlier but this investigation concerns in vivo existance of RuBisCO crystals in anthers and leaves ofsugarbeets. For the identification of in vivo protein crystals it is important to be able to determinethe unit cell of cytochemically identified crystals in the same image. In order to obtain the best combination of optimal contrast and resolution we have studied different staining and electron accelerating voltages. It is known that embedding and sectioning can cause deformation and obscure the unit cell parameters.

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