Brief Summary of Minutes of Annual Meeting

Scientific presentations (Presenters and scientific summary/goals)

Jeffrey Harper: Jeff Harper reported on development and use of a more sensitive fluorescent reporter of cellular calcium levels. Using this reporter, he shows calcium signaling occurs in response to heat stress within minutes, and that calcium levels in growing pollen tubes oscillate dramatically. Heat stress is a major loss of crop productivity, and further isolation of the underlying signals and their timing will clarify direct effects of heat on photosynthesis as opposed to responses.

Michael Giroux: Reports on the attempt to modulate starch biosynthesis to increase seed yield in wheat. Unexpectedly, measurements of flag-leaf starch content in two segregating populations showed a negative correlation to yield. The next step is to understand the outliers in the population with both high yield and leaf starch, and genome-wide association mapping will be used to identify causative loci.

Julie Stone and Nicole Buan: Reported that exogenous application of an archaeal antioxidant improves crop growth and yield. Multiple hormone responses are triggered, the redox state of the chloroplast is changed, and the level of non-photochemical quenching in high light appears to be decreased. The impact on photosynthesis will be further investigated and native production of the archaeal antioxidant is being attempted.

Rob Aiken: Reported measured carbon dioxide assimilation rates and variation in canopy temperature throughout the day in grain sorghum cultivars differing in putative transpiration rate limitation. Biophysical analysis of multispectral reflectance and thermal emittance will support genomic inquiries to limited transpiration.

Ru Zhang: Reported that moderate high temperatures accelerate carbon metabolism while reducing biomass accumulation in nutrient limited Chlamydomonas reinhardtii. Limiting levels of heat reduced oxygen evolution, gluconeogenesis, glyoxylate cycle, and increased cell size while reducing cell density.

Christoph Benning: Reported that a unique trans fatty acid present in the thylakoid membrane esterified to phosphatidylglycerol is inversely correlated with photosynthetic performance only under temperature stress. A large screen of the effects of temperature on thylakoid lipid mutant photosynthetic parameters revealed many lipids are critical for regulation of photosynthetic efficiency.

Felix Fritschi: Reported that starch accumulates in the leaves of N-deficient maize instead of being used to support kernel growth and development. Export is possible and enzymes for starch digestion are present. Accumulation of photosynthate as starch in leaves which are meant to support grain filling is inefficient and might block efforts to improve yield through photosynthetic manipulation. Also reported is that the University of Missouri’s Plant Transformation Core Facility is back as a public service center.

Tom Sharkey: Reported that the primary source of carbon dioxide released during photosynthesis may be from cytosolic 6-phosphogluconate dehydrogenase. The rate of carbon dioxide release appears to be variable and may slow at high rates of photosynthesis.

Scott McAdam: Reported that in highly drought-tolerant species, the hormone abscisic acid peaks at an intermediate leaf water potential. The expectation was that abscisic acid would peak when stomata close, during initial water potential deficit. The implication is that there are multiple unknowns in the connection between abscisic acid and stomatal opening. Importantly, this is a major mechanism for adapting photosynthesis to drought.

 John Cushman: Reported progress on understanding the genome and diversity of cactus pear. Cactus pear is a CAM photosynthesizer highly adapted to arid conditions and capable of high biomass production with minimal water input.

Tasios Melis: Reported multiple strategies for production of proteins of non-bacterial origin in cyanobacteria. These have been used for single proteins and for production of pathways.

Rebecca Roston: Reported visualization strategies for contact sites between the thylakoid and inner envelope membranes of chloroplasts.

Business Meeting Summary

Renewal of NC1200 in 2021. Rob Aiken, lead author, reports on writing progress, outstanding requests, and submission progress of the renewal proposal. Appendix E form submission is reported and members are notified of the Appendix E submission process. The proposal is on track for a December submission. Christoph Benning remains as Administrative Advisor.

Membership. New members were briefly discussed, and the decision was made to consider members further after the proposal is renewed. Tom Sharkey will retire from the project in 2022 in anticipation of retiring from research.

The 2022 meeting will be held in Reno organized by John Cushman.

The 2023 meeting will be held in Indiana organized by Scott McAdam.

Activities in 2021 are summarized under the different objectives.

Objective 1. Identify Strategies to optimize the assembly and function of the photosynthetic membrane.

• We improved our characterization of chloroplast lipases. Monogalactolipid is critical for photosynthetic efficiency and requires a phosphatidic acid phosphatase in its synthesis. Triple mutants of the major plastid phosphatidic acid phosphatase family (LPPγ, LPPε1, LPPε2) were constructed. In labeling experiments, isolated chloroplasts from triple, double and single mutants are all still capable of synthesizing MGDG. Hence, there must be additional phosphatases involved in synthesis of monogalactolipid.
• The plastid rhomboid-like protease protein RBL10 is implicated in development of the photosynthetic membrane. We published last years’ work identifying potential interactors of RBL10. One of them is ACP4 involved in fatty acid metabolism in chloroplasts that we further investigated by constructing rbl10, acp4 double mutants and labeling of isolated chloroplasts. Both mutations affect the chloroplast PA pool, but in opposite ways. Assay development for recombinant forms of RBL10 has not yet been successful and efforts continue.
• We continued the analysis of the reaction mechanism, activation, and function of the unusual FAD4 desaturase of Arabidopsis. FAD4 is responsible for the formation of a phosphatidylglycerol species in chloroplasts that contains a unique trans fatty acid. A specific peroxiredoxin is required for the activity of FAD4 in vivo and in vitro. We showed an inverse relationship between the abundance of the trans fatty acid and photosynthetic performance under low temperatures in Arabidopsis. We are now investigating this system in Chlamydomonas. In preliminary experiments, we observed differences in overall lipid turnover and biosynthesis in fad4 and prxq
• We finalized and published our studies on thylakoid ion transporter and channels. This study combines experimental data with a mathematical simulation model that describes photosynthetic light-dependent and light-independent reactions. We found that the concerted action of the potassium/proton antiporter KEA3 and the voltage-gated chloride channel VCCN1 fine-tune the establishment of the proton gradient across thylakoid membranes and photoprotective non-photochemical quenching.
• We finalized and published a multi-year project on the response of the photosynthetic apparatus to dehydration in the resurrection model plant Craterostigma. The results indicate that the developmental state of the Craterostigma plants determine whether more photoprotective or more degradation-based processes are activated during dehydration.
• The structural and functional characterization of changes in stacked and unstacked thylakoid membranes during state transitions were finalized. In photosynthesis state transition is a regulatory mechanism that balances light distribution to both photosystems under low light. A manuscript is in preparation.
• We produced the first computer-generated coarse-grain protein maps for stacked thylakoid membranes based on cryo-scanning electron microscopic images (provided by collaboration partners in Israel) and quantitative biochemical and biophysical data.
• We published a paper on rice plastidial phosphorylase. The study indicates that the phosphorylase in chloroplasts interacts with photosystem I in thylakoid membranes and could have a direct regulatory function on photosynthetic electron transport.
• We developed and improved computer-based quantitative analysis tools for the extraction of structural thylakoid membrane parameters from thin-section electron microscopic images. These tools were used to characterize light-induced ultrastructural changes thylakoid ion transport/channel mutants.
• We have developed multiple fluorescent markers of thylakoid/inner envelope membrane contact sites. To investigate the conditions increasing inner envelope and thylakoid membrane connectivity, we will pair these with traditional microscopy to screen stress conditions that show the largest increase in contact sites.
• We have generated candidate lists of proteins at thylakoid/inner envelope membrane contact sites using traditional fractionation techniques and predictions of chloroplast homologs of contact site proteins of other membranes. We have begun to screen these.

Objective 2. Identify strategies to modify biochemical and regulatory factors that impact the photosynthetic capture and photorespiratory release of CO2.

• We measured Rubisco and Phosphoenolpyruvate carboxylase (PEPC) kinetic properties and isotope discrimination using membrane inlet mass spectrometry (MIMS). Recently, we tested if isotopic carbon discrimination is correlated to changes in the elementary rate constants that occur in response to temperature changes in Oryza sativa Rubisco (Boyd et al. in preparation). However, Rubisco discrimination was constant with temperature suggesting that kinetic changes in this species were instead associated with continual deactivation of the enzyme with temperature. Additionally, we modified specific amino acid residues in PEPC to determine their influence on HCO₃^-
• Day respiration, or CO₂ release in the light, reduces the rate of photosynthesis, but the origin of the carbon has been unclear. We showed that this CO₂ originates from glucose 6-phosphate in the cytosol. We identified three different ways that carbon enters the Calvin-Benson cycle and carried out a comprehensive mass flux analysis. We were able to explain why Calvin-Benson cycle intermediates do not become fully labeled when photosynthesizing leaves are fed labeled CO₂. These experiments also showed that isoprene labeling is an appropriate non-destructive measure for studying labeling of the Calvin Benson cycle.
• We performed an integrated genomic and transcriptomic analysis to explore the molecular basis of convergent evolution of C₄ photosynthesis in the grass family. Our results showed that C₄ genes from independent C₄ grass lineages have evolved from a set of common ancestral genes and C₄ genes shared similar cis-elements across independent C₄
• We developed a simple and efficient tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) system for functional analysis of genes in zoysiagrass. The VIGS system provides a fast and efficient toolbox for high-throughput functional genomics in zoysiagrass species, which could potentially be applied to study gene regulation and regulatory network of C₄ metabolic activities.
• We engineered synthetic crassulacean acid metabolism (CAM) and tissue succulence to improve water-use efficiency (WUE), drought tolerance, and plant productivity.
• We improved proteomic resources for membrane-associated proteins in the facultative CAM model Mesembryanthemum crystallinum using free flow electrophoresis techniques and to provide evidence for multiple subcellular localization of selected proteins.

Objective 3. Mechanisms regulating photosynthate partitioning

• We discovered that the plastidial phosphorylase (Pho1) modulates photosystem I (PSI) activity via its interaction with PsaC, the terminal electron acceptor-donor of PSI. Pho1 has an extra peptide (L80) not present in the human and yeast phosphorylase enzymes.  The L80 peptide acts as a negative regulator of photosynthesis, making Pho1 is a potential target for enhancing cereal grain production.  This year we extended the study on the Pho1 protein interactome of PSI components.  We validated the interaction of Pho1 with PsaC by yeast 2-hybrid by bimolecular florescence complementation (BiFC) assays.  Based on yeast 2-hybrid results, Pho1 can interact directly with PsaD, which, in turn, binds to PsaC in the PSI structure.  Pho1 may also interact with ferredoxin.  These results suggest that Pho1 may form higher-order complexes linking components of PSI with reductant proteins (ferredoxin). 
• We generated catalytic mutant versions of Pho1 and Pho1ΔL80 and expressed these genes in pho1^- rice line BMF136. Analysis of grain phenotype indicated no significant differences in grain phenotype between Pho1, Pho1ΔL80, and BMF136.  Hence, catalytic-active Pho1ΔL80 is required to enhance grain size.  
• To identify the negative regulatory elements of the L80 peptide, we deleted selected regions of the peptide and expressed the resulting Pho1 variant proteins in transgenic rice. These transgenic rice lines are currently being grown.
• We studied the triose phosphate utilization (TPU) limitation of photosynthesis, the situation where photosynthesis can go faster than the plant can process its products. This year we showed that when plants are put into conditions that cause TPU, carbon metabolism and electron transport are regulated to match the lowered demand. Within a short time, the reduced rates of carbon metabolism results in a longer-term reduction in carbon fixation capacity. Photosynthesis therefore begins to look like it is limited by rubisco capacity even though it was limited TPU capacity that reduced rubisco capacity. This is why plants rarely appear TPU limited but very frequently are close to TPU limitation.
• We completed flux maps on tobacco. Tobacco produce high levels of lipids that could be an important future crop or model for lipid-based biofuel production. Isotopes were used to examine the tradeoff in starch production that is characteristic of some plants including tobacco, but which was reduced considerably with carbon repartitioned to make the enhanced lipid content in leaves.
• We have made good progress on malic enzyme overexpression lines in soybean to see if this impacts the production of oil content. The work describes a small boost in oil depending on the subcellular location of the malic enzyme overexpression. When expressed in the chloroplast, enhanced levels of monounsaturated oil is observed. When malic enzyme is expressed in the mitochondria, increased levels of pyruvate-derived amino acids were observe, especially alanine.

Objective 4: Developmental and Environmental Limitations to Photosynthesis

• Abscisic acid-activated protein kinase (AAPK) is a positive regulator that can enhance abscisic acid signaling including stomatal closure. We mis-regulated AAPK in soybean and tested physiological and transcriptional drought responses. We found AAPK overexpression lines exhibited enhanced drought tolerance. Notable transcriptional responses included a dehydration-stimulated phosphatase. To determine the role of the dehydration-stimulated phosphatase in regulating rice drought responses, overexpression lines of fructose-1,6-bisphosphatase were generated in rice.
• We have conducted studies examining the environmental triggers of embolism resistance in the xylem, a critical determinant of hydraulic supply to leaves and thus productivity.  We have found that regardless of light level or position in the canopy both leaf and stem embolism resistance is highly conserved within an individual.  This result is critical for our on-going work investigating the importance of embolism in determining leaf gas exchange over a growing season.  We are currently monitoring leaf gas exchange, foliage hormone levels, water potential, hydraulic conductance and embolism resistance in trees native to the Midwest in a forest rainout shelter experiment.
• As part of an ongoing investigation into the mechanism of stomatal regulation during long term drought in land plants, we have found that in species that have evolved highly resistant xylem to embolism formation, foliage abscisic acid (ABA) levels decline once leaves dry to beyond turgor loss point.  This decline in ABA levels is due to the biochemical deactivation of ABA biosynthesis, the conversion of ABA to the conjugate ABA glucose ester and the export of this compound from the leaf in the phloem.  This mechanism is shared by both angiosperms and gymnosperms.  Through these experiments we have discovered that the stomata of angiosperms can be passively closed under long term drought.  This new discovery resolves a 150 year old, unanswered question about the importance of metabolism or biophysical processes in regulating the stomata of angiosperms.
• We obtained the first long-term vegetative and fruit biomass production data for three different cactus pear (Opuntia) species over five years in the USA. These results are being used to develop life cycle assessment and life cycle costing analyses for bioenergy production models.
• We used molecular barcoding to characterize a soil microbial consortium and identify key eubacterial and fungal isolates and their excreted enzymes capable of degrading cactus pear (Opuntia ficus-indica) cladode biomass for biofuel production systems.
• We improved the development of genomic and transcriptomic resources for cochenillifera (diploid) and Opuntia spp. accessions of the USDA-ARS national Opuntia germplasm collection.
• We published results showing that a triple loss-of-function for three Ca²⁺ pumps located in the ER (ACA1, 2, 7, Autoinhibited Calcium ATPases) can result in Ca²⁺ signals with higher magnitudes and durations (Ishka et. al., 2021).  This deletion of ER located Ca²⁺ pumps correlates with an increased frequency of salicylic acid dependent lesions in rosette leaves.  In addition, this mutant also shows a potential change in Ca²⁺ storage in the ER, which can alter the dynamics of guard cells and plant water use efficiency (Jezek et. al., 2021). These studies establish the importance of ER Ca²⁺ pumps in shaping the information content of Ca²⁺ signals that impact biotic and abiotic stress responses. 
• We developed a new Ca²⁺ reporter as a fusion between mCherry and GCaMP6f that allows for more confident imaging of Ca²⁺ signals in response to biotic and abiotic stimuli. This reporter provides a ratiometric measurement that allows more accurate comparisons of signal strength between different tissues, cell types, and subcellular locations.
• We continued researching the role of Ca²⁺ dependent protein kinases (CPKs) in pollen. We identified two features in CPK34 that can be swapped into CPK16 to permit a modified CPK16 to rescue a near pollen-sterile knockout of CPK17/34.  This provides new insights into the biochemical and functional differences for the 34 CPKs expressed in Arabidopsis.
• We continued our investigation of agronomic practices affecting yield through photosynthetic impacts. Previously, we showed that narrow row spacing had the strongest impact on yield. We have updated this with additional factors including plant population and nutrient applications. Narrow rows and the combination of P-S-Zn and K-B fertility were the factors that provided the most significant yield increases compared to the standard control. Increasing plant population from 79,000 to 109,000 plants ha^-1 reduced the yield gap when all other inputs were applied at the enhanced level.
• We quantified carbon dioxide assimilation rates and diel variation in canopy temperature for field trials of grain sorghum cultivars differing in the putative limited transpiration trait. Images of visible, near-infrared reflectance and thermal emittance were acquired for this trial and related mapping populations.
• We quantified the impacts of high temperature stress under controlled environment and field conditions. These studies improved our understanding of physiological and biochemical basis of high temperature tolerance in sorghum and wheat.
• Outreach (all objectives): We developed short videos of our research and shared them on virtual platforms (e.g., social media and website). We also presented the research virtually at multiple international meetings.

Outputs

See Publications, below.

Plans for the coming year

Objective 1. Identify Strategies to optimize the assembly and function of the photosynthetic membrane.

• We will complete the analysis of the three LPP proteins in Arabidopsis chloroplasts and initiate a search for additional PA phosphatases in the chloroplast.
• We will complete our analysis of ACP4 and RBL10 interaction.
• We will continue our analysis of the function of chloroplast trans fatty acids to explore its role in protection of the photosynthetic membrane in Arabidopsis and Chlamydomonas.
• We will finalize the project on the light-induced lateral redistribution of the cytochrome b6f in thylakoid membranes by combining electron microscopic, biochemical and spectroscopic methods.
• We will continue the work on light-induced ultrastructural changes in thylakoid membranes and evaluate functional consequences.
• We will further develop dynamic coarse-grain computer models of thylakoid membranes to understand structure-function relationship for electron transport and light harvesting.
• We will screen our lists of putative chloroplast contact site proteins by co-localizing them with our fluorescent reporters and using traditional fractionation/electron microscopy techniques.
• We will continue refining lists of putative proteins using chloroplast fractionation techniques.
• We will test our fluorescent reporters of chloroplast membrane contact sites using electron microscopy based localization.

Objective 2. Identify strategies to modify biochemical and regulatory factors that impact the photosynthetic capture and photorespiratory release of CO2.

• We will determine kinetic parameters driving the temperature response of Rubisco kinetics from two diverse C₄
• We will determine if substitutions of specific amino acid residues in C₄ isoforms of PEPC drive variation in kinetic properties.
• We will use ccomparative genomics and evolutionary genomics to understand the molecular changes linked to C₄ and CAM photosynthesis evolution.
• We will identify a set of cis-elements that are involved in regulating C₄ and CAM photosynthesis.
• We will make progress towards the optimization of synthetic CAM in Arabidopsis and engineered with tissue succulence in Glycine max.

Objective 3. Mechanisms regulating photosynthate partitioning

• We will validate the interactions of Pho1 with PsaD and ferredoxin by BiFC.
• We will identify the regulatory sites of L80 by studying the growth and grain properties of transgenic rice lines expressing variant Pho1 containing various parts of the L80 deleted.
• We will submit manuscripts on malic enzyme overexpression and on high oil tobacco lines.

Objective 4: Developmental and Environmental Limitations to Photosynthesis

• We will continue to generate overexpression lines of fructose-1,6-bisphosphatase and test stress tolerance profiles of gene-overexpressing lines.
• We will publish the results of overexpression of AAPK-like protein kinase on improving drought response and tolerance in soybean.
• We will continue to investigate the underlying developmental differences that allow stomata to open and attain very high rates of gas exchange.
• We will explore the role of the hormone ABA on limiting gas exchange during drought; and how the evolution of the stomatal response to this hormone led to the ecological success of angiosperms.
• We continue to investigate the determinants of the lethal thresholds for plants during drought and how these might be altered to prolong productivity during periods of water deficit.
• We will report on the results of cladode area index (CAI) models for multiple accessions of Opuntia, life cycle assessment (LCA) and life cycle costing (LCC) analyses related to bioenergy production from ficus-indica. We will also report on the causative agents of Opuntia stunting disease and the genetic basis of spine and glochid formation.
• We will continue work on molecular genotyping and phylogeny of >280 accessions within the national USDA-ARS Opuntia germplasm collection and transcriptome and genome sequencing of two reference species: cochenillifera (diploid) and O. ficus-indica (octoploid).
• We will continue our characterization of the phenotypic diversity within the national USDA-ARS Teff (Eragrostis tef) germplasm collection, including two drought-tolerant tef accessions, and report on the high-quality transcriptome and genome sequence of one of the drought drought-tolerant E. tef accessions.
• We will test candidate genes for their ability to improve heat-stress tolerance in pollen.
• We will determine how Ca²⁺signals are modified by regulation of Ca²⁺pumps and channels.  
• We will investigate the role of lipid flippases in regulating heat-stress tolerance. 
• We will continue to study effects of fertilizers and foliar protectants on crop photosynthesis and productivity.
• We will investigate alternate models of hybrid characterization for yield production.
• We will explore biologicals as an agronomic management strategy to increase nutrient use and/or photosynthetic efficiency.
• We will continue to test how changes in row spacing interact with other management practices.
• We will collect multispectral reflectance and thermal emittance of wheat cultivars in a nationally-coordinated consortium of public wheat breeders.
• We will perform biophysical analysis of multispectral reflectance and thermal emittance of sorghum to support genomic investigations in the limited transpiration trait.
• We will assess the physiological and molecular impact of high night temperature during grain filling on carbon balance, yield, grain quality in corn hybrids.

Adotey, R. E., Patrignani, A., Bergkamp, B., Kluitenberg, G., Prasad, P. V. V., & Jagadish, S. V. K. (2021). Water-deficit stress alters intra-panicle grain number in sorghum. Crop Science, 61(4), 2680-2695. doi:10.1002/csc2.20532

Aiken, R.M. Testing efficacy of plant growth regulator products for enhanced winter wheat grain yield and quality. Kansas Field Research 2021.

Avila, R. T., Cardoso, A. A., Batz, T. A., Kane, C. N., DaMatta, F. M., & McAdam, S. A. M. (2021). Limited plasticity in embolism resistance in response to light in leaves and stems in species with considerable vulnerability segmentation. Physiologia Plantarum, 172(4), 2142-2152. doi:10.1111/ppl.13450

Bheemanahalli, R., Wang, C. X., Bashir, E., Chiluwal, A., Pokharel, M., Perumal, R., . . . Jagadish, S. V. K. (2021). Classical phenotyping and deep learning concur on genetic control of stomatal density and area in sorghum. Plant Physiology, 186(3), 1562-1579. doi:10.1093/plphys/kiab174

Blair, B. B., Yim, W. C., & Cushman, J. C. (2021). Characterization of a microbial consortium with potential for biological degradation of cactus pear biomass for biofuel production. Heliyon, 7(8), e07854. doi:10.1016/j.heliyon.2021.e07854

Borja Reis, A. F. d., Rosso, L. H. M., Davidson, D., Kovács, P., Purcell, L. C., Below, F. E., . . . Ciampitti, I. A. (2021). Sulfur fertilization in soybean: A meta-analysis on yield and seed composition. European Journal of Agronomy, 127, 126285. doi:https://doi.org/10.1016/j.eja.2021.126285

Cook, R., Lupette, J., & Benning, C. (2021). The Role of Chloroplast Membrane Lipid Metabolism in Plant Environmental Responses. Cells, 10(3), 706. doi:10.3390/cells10030706

Cross, P., Iisa, K., To, A., Nimlos, M., Carpenter, D., Mayer, J. A., . . . Mukarakate, C. (2021). Multiscale Catalytic Fast Pyrolysis of Grindelia Reveals Opportunities for Generating Low Oxygen Content Bio-Oils from Drought Tolerant Biomass. Energy & Fuels. doi:10.1021/acs.energyfuels.1c02403

Dani, K. G. S., Pollastri, S., Pinosio, S., Reichelt, M., Sharkey, T. D., Schnitzler, J. P., & Loreto, F. (2021). Isoprene enhances leaf cytokinin metabolism and induces early senescence. New Phytologist. doi:10.1111/nph.17833

DiMario, R. J., Kophs, A. N., Pathare, V. S., Schnable, J. C., & Cousins, A. B. (2021). Kinetic variation in grass phosphoenolpyruvate carboxylases provides opportunity to enhance C-4 photosynthetic efficiency. Plant Journal, 105(6), 1677-1688. doi:10.1111/tpj.15141

Gonzalez-Esquer, C. R., Ferlez, B., Weraduwage, S. M., Kirst, H., Lantz, A. T., Turmo, A., . . . Kerfeld, C. A. (2021). Validation of an insertion-engineered isoprene synthase as a strategy to functionalize terpene synthases. Rsc Advances, 11(48), 29997-30005. doi:10.1039/d1ra05710c

Gregory, L. M., McClain, A. M., Kramer, D. M., Pardo, J. D., Smith, K. E., Tessmer, O. L., . . . Sharkey, T. D. (2021). The triose phosphate utilization limitation of photosynthetic rate: Out of global models but important for leaf models. Plant Cell and Environment, 44(10), 3223-3226. doi:10.1111/pce.14153

Guo, Q., Liu, L., Yim, W. C., Cushman, J. C., & Barkla, B. J. (2021). Membrane Profiling by Free Flow Electrophoresis and SWATH-MS to Characterize Subcellular Compartment Proteomes in Mesembryanthemum crystallinum. International Journal of Molecular Sciences, 22(9). doi:10.3390/ijms22095020

Jagadish, S. V. K., Way, D. A., & Sharkey, T. D. (2021). Plant heat stress: Concepts directing future research. Plant Cell and Environment, 44(7), 1992-2005. doi:10.1111/pce.14050

Jezek, M., Silva-Alvim, F. A. L., Hills, A., Donald, N., Ishka, M. R., Shadbolt, J., . . . Blatt, M. R. (2021). Guard cell endomembrane Ca2+-ATPases underpin a 'carbon memory' of photosynthetic assimilation that impacts on water-use efficiency. Nature Plants, 7(9), 1301-+. doi:10.1038/s41477-021-00966-2

Kambhampati, S., Aznar-Moreno, J. A., Bailey, S. R., Arp, J. J., Chu, K. L., Bilyeu, K. D., . . . Allen, D. K. (2021). Temporal changes in metabolism late in seed development affect biomass composition. Plant Physiol, 186(2), 874-890. doi:10.1093/plphys/kiab116

Kang, B. H., Anderson, C. T., Arimura, S. I., Bayer, E., Bezanilla, M., Botella, M. A., . . . Zolman, B. K. (2021). A glossary of plant cell structures: Current insights and future questions. Plant Cell. doi:10.1093/plcell/koab247

Kirchhoff, H. (2021). Proteoliposomes for Studying Lipid-protein Interactions in Membranes in vitro. Bio Protoc, 11(20), e4197. doi:10.21769/BioProtoc.4197

Koper, K., Hwang, S. K., Singh, S., & Okita, T. W. (2021). Source-sink relationships and its effect on plant productivity: manipulation of primary carbon and starch metabolism. In Genome Engineering for Crop Improvement (pp. 1-31). Springer Nature. 10.1007/978-3-030-63372-1_1

Koper, K., Hwang, S. K., Wood, M., Singh, S., Cousins, A., Kirchhoff, H., & Okita, T. W. (2021). The Rice Plastidial Phosphorylase Participates Directly in Both Sink and Source Processes. Plant and Cell Physiology, 62(1), 125-142. doi:10.1093/pcp/pcaa146

Koper, K., Hwang, S. K., Wood, M., Singh, S., Cousins, A., Kirchhoff, H., & Okita, T. W. (2021). The Rice Plastidial Phosphorylase Participates Directly in Both Sink and Source Processes. Plant Cell Physiol, 62(1), 125-142. doi:10.1093/pcp/pcaa146

Lavell, A., Smith, M., Xu, Y., Froehlich, J. E., de la Mora, C., & Benning, C. (2021). Proteins associated with the Arabidopsis thaliana plastid rhomboid-like protein RBL10. Plant Journal, 108(5), 1332-1345. doi:10.1111/tpj.15514

Li, M., Svoboda, V., Davis, G., Kramer, D., Kunz, H. H., & Kirchhoff, H. (2021). Impact of ion fluxes across thylakoid membranes on photosynthetic electron transport and photoprotection. Nat Plants, 7(7), 979-988. doi:10.1038/s41477-021-00947-5

Liu, J. J., Cook, R., Danhof, L., Lopatto, D., Stoltzfus, J. R., & Benning, C. (2021). Connecting research and teaching introductory cell and molecular biology using an Arabidopsis mutant screen. Biochemistry and Molecular Biology Education, 49(6), 926-934. doi:10.1002/bmb.21579

Lopez-Marques, R. L., Davis, J. A., Harper, J. F., & Palmgren, M. (2021). Dynamic membranes: the multiple roles of P4 and P5 ATPases. Plant Physiology, 185(3), 619-631. doi:10.1093/plphys/kiaa065

Mayer, J. A., Wone, B. W. M., Alexander, D. C., Guo, L., Ryals, J. A., & Cushman, J. C. (2021). Metabolic profiling of epidermal and mesophyll tissues under water-deficit stress in Opuntia ficus-indica reveals stress-adaptive metabolic responses. Funct Plant Biol, 48(7), 717-731. doi:10.1071/FP20332

Meng, X., Liang, Z., Dai, X., Zhang, Y., Mahboub, S., Ngu, D. W., . . . Schnable, J. C. (2021). Predicting transcriptional responses to cold stress across plant species. Proceedings of the National Academy of Sciences, 118(10), e2026330118. doi:10.1073/pnas.2026330118

Monson, R. K., Weraduwage, S. M., Rosenkranz, M., Schnitzler, J. P., & Sharkey, T. D. (2021). Leaf isoprene emission as a trait that mediates the growth-defense tradeoff in the face of climate stress. Oecologia, 197(4), 885-902. doi:10.1007/s00442-020-04813-7

Müh, F., van Oort, B., Puthiyaveetil, S., & Kirchhoff, H. (2021). Reply to: Is the debate over grana stacking formation finally solved? Nature Plants, 7(3), 279-281. doi:10.1038/s41477-021-00881-6

Neupane, D., Mayer, J. A., Niechayev, N. A., Bishop, C. D., & Cushman, J. C. (2021). Five-year field trial of the biomass productivity and water input response of cactus pear (Opuntia spp.) as a bioenergy feedstock for arid lands. GCB Bioenergy, 13(4), 719-741. doi:https://doi.org/10.1111/gcbb.12805

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