Gerald E. Edwards's research while affiliated with Washington State University and other places

Publications (293)

Article
C2 photosynthesis is characterized by recapturing photorespiratory CO2 by RuBisCO in Kranz‐like cells and is therefore physiologically intermediate between C3 and C4 photosynthesis. C2 can be interpreted as an evolutionary precursor of C4 and/or as the result of hybridization between a C3 and C4 lineage. ●We compared the expression of photosyntheti...
Preprint
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C2 photosynthesis is characterized by recapturing photorespiratory CO2 by RuBisCO in Kranz-like cells and is therefore physiologically intermediate between C3 and C4 photosynthesis. C2 is either interpreted as an evolutionary precursor of C4 or as the result of hybridization between a C3 and C4 lineage. We compared the expression of photosynthetic...
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Background: Chloroplast genome information is critical to understanding forms of photosynthesis in the plant kingdom. During the evolutionary process, plants have developed different photosynthetic strategies that are accompanied by complementary biochemical and anatomical features. Members of family Chenopodiaceae have species with C3 photosynthe...
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The engineering process of C4 photosynthesis into C3 plants requires an increased activity of phosphoenolpyruvate carboxylase (PEPC) in the cytosol of leaf mesophyll cells. The literature varies on the physiological effect of transgenic maize (Zea mays) PEPC (ZmPEPC) leaf expression in Oryza sativa (rice). Therefore, to address this issue, leaf–atm...
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Halopeplis perfoliata, a C3 halophyte with succulent photosynthetic shoots, is a common primary producer of the coastal marshes of the Saharo‐Arabian region. Little information is available on the salinity tolerance mechanisms of this perennial halophyte. Growth, physiological and biochemical adaptations to saline conditions (0, 150, 300 and 600 mM...
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The influence of reduced glycine decarboxylase complex (GDC) activity on leaf-atmosphere CO2 and 13CO2 exchange was tested in transgenic Oryza sativa with the knocked down (KD) of the GDC H-subunit in the leaf M cells. Leaf measurements on transgenic (gdch-KD) and wild-type (WT) plants were carried out in the light under photorespiratory and low-ph...
Article
Photosynthesis in different organs of Cleome was analysed in four species known to have differences in leaf photosynthesis: Cleome africana Botsch. (C3), Cleome paradoxa R.Br. (C3-C4 intermediate), Cleome angustifolia Forssk. and Cleome gynandra L. (C4). The chlorophyll content, carbon isotope composition, stomatal densities, anatomy, levels and co...
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In C4 photosynthesis, pyruvate orthophosphate dikinase (PPDK) catalyzes the regeneration of phosphoenolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characterized, a genetic analysis of PPDK has not been reported. In this study, we utilize the maize transposable elements Mutator and Ds to generat...
Preprint
The efficiency of photosynthetic carbon assimilation in higher plantsfaces significant limitations due to the oxygenase activity of the enzyme Rubisco,particularly under warmer temperatures or water stress. A drop in atmospheric CO2and rise in O2 as early as 300 mya provided selective pressure for the evolution ofmechanisms to concentrate CO2 aroun...
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Salt-tolerant grasses of warm sub-tropical ecosystems differ in their distribution patterns with respect to salinity and moisture regimes. Experiments were conducted on CO2 fixation and light harvesting processes of four halophytic C4 grasses grown under different levels of salinity (0, 200 and 400 mM NaCl) under ambient environmental conditions. T...
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While many C4 lineages have Kranz anatomy around individual veins, Salsoleae have evolved the Salsoloid Kranz anatomy where a continuous dual layer of chlorenchyma cells encloses the vascular and water-storage tissue. With the aim of elucidating the evolution of C4 photosynthesis in Salsoleae, a broadly sampled molecular phylogeny and anatomical su...
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Portulacaceae is a family that has considerable diversity in photosynthetic phenotypes. It is one of 19 families of terrestrial plants where species having C4 photosynthesis have been found. Most species in Portulaca are in the alternate-leaved (AL) lineage, which includes one clade (Cryptopetala) with taxa lacking C4 photosynthesis and three clade...
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Bienertia cycloptera belongs to a diverse set of plants, recently discovered to perform C4 photosynthesis within individual mesophyll cells. How these plants accomplish high photosynthetic efficiency without adopting Kranz anatomy remains unanswered. By modelling the processes of diffusion, capture, and release of carbon dioxide and oxygen inside a...
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Temporal and spatial patterns of photosynthetic enzyme expression and structural maturation of chlorenchyma cells along longitudinal developmental gradients were characterized in young leaves of two single cell C4 species, Bienertia sinuspersici and Suaeda aralocaspica. Both species partition photosynthetic functions between distinct intracellular...
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The two carboxylation reactions performed by phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) are vital in the fixation of inorganic carbon for C4 plants. The abundance of PEPC is substantially elevated in C4 leaves, while the location of Rubisco is restricted to one of two chloroplast types. Thes...
Article
Kranz C4 species strictly depend on separation of primary and secondary carbon fixation reactions in different cell types. In contrast, the single-cell C4 (SCC4) species Bienertia sinuspersici utilizes intracellular compartmentation including two physiologically and biochemically different chloroplast types. However, information on identity, locali...
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Three C4 acid decarboxylases, phosphoenolpyruvate carboxykinase (PEPCK), NADP-malic enzyme (NADP-ME), and NAD-malic enzyme (NAD-ME) were recruited from C3 plants to support C4 photosynthesis. In Poaceae, there are established lineages having PEPCK type species, and some NADP-ME lineages in which PEPCK contributes to C4. Besides family Poaceae, rece...
Article
Another “green revolution” is needed for crop yields to meet the demands for food and this has provided a new focus on photosynthesis research. Many important crops have the C3 photosynthetic pathway and a range of options for enhancing leaf photosynthesis in C3 species are being tested. George Bowes’ pioneering research elucidated the inducible si...
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Photosynthesis in C3-C4 intermediates reduces carbon loss by photorespiration through refixing photorespired CO2 within bundle sheath cells. This is beneficial under warm temperatures where rates of photorespiration are high; however, it is unknown how photosynthesis in C3-C4 plants acclimates to growth under cold conditions. Therefore, the cold to...
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In subfamily Suaedoideae, four independent gains of C4 photosynthesis are proposed, which includes two parallel origins of Kranz anatomy (sections Salsina and Schoberia) and two independent origins of single-cell C4 anatomy (Bienertia and Suaeda aralocaspica). Additional phylogenetic support for this hypothesis was generated from sequence data of t...
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In family Cleomaceae there are NAD-malic enzyme-type C4 species having different forms of leaf anatomy. Leaves of Cleome angustifolia have Glossocardioid-type anatomy with a single complex Kranz unit which surrounds all the veins, while C. gynandra has Atriplicoid anatomy with multiple Kranz units, each surrounding an individual vein. Biochemical a...
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In the model single-cell C4 plant Bienertia sinuspersici, chloroplast- and nuclear-encoded photosynthetic enzymes, characteristically confined to either bundle sheath or mesophyll cells in Kranz-type C4 leaves, all occur together within individual leaf chlorenchyma cells. Intracellular separation of dimorphic chloroplasts and key enzymes within cen...
Article
Traditionally, it was believed that C4 photosynthesis required two types of chlorenchyma cells to concentrate CO2 within the leaf. However, several species have been identified that perform C4 photosynthesis using dimorphic chloroplasts within an individual cell. The goal of this research was to determine how growth under limited light affects leaf...
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Portulacaceae is a family with a remarkable diversity in photosynthetic pathways. This lineage not only has species with different C4 biochemistry (NADP-ME and NAD-ME types) and C3-C4 intermediacy, but also displays different leaf anatomical configurations. Here we addressed the evolutionary history of leaf anatomy and photosynthetic pathways in Po...
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In subfamily Salsoloideae (family Chenopodiaceae) most species are C4 plants having terete leaves with Salsoloid Kranz anatomy characterized by a continuous dual chlorenchyma layer of Kranz cells (KCs) and mesophyll (M) cells, surrounding water storage and vascular tissue. From section Coccosalsola sensu Botschantzev, leaf structural and photosynth...
Article
Oryza, which includes rice and wild relatives, is a useful genus to study leaf properties in order to identify structural features that control CO2 access to chloroplasts, photosynthesis, water use efficiency and drought tolerance. Traits, 26 structural and 17 functional, associated with photosynthesis and transpiration were quantified on 24 access...
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Photosynthetic performance of plants is crucially dependent on the mobility of the molecular complexes that catalyze conversion of sunlight to metabolic energy equivalents in the thylakoid membrane network inside chloroplasts. The role of the extensive folding of thylakoid membranes leading to structural differentiation into stacked grana regions a...
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David Alan Walker, Emeritus Professor of Biology, University of Sheffield, UK and Fellow of the Royal Society, died on February 13, 2012. David had a marvelous 60 year career as a scientist, during which he was a researcher, mentor, valued colleague, and a prolific writer in the field of photosynthesis. His career was marked by creative breakthroug...
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We provide here insights on the life and work of Berger C. Mayne (1920-2011). We remember and honor Berger, whose study of photosynthesis began with the most basic processes of intersystem electron transport and oxygen evolution, continued with application of fluorescence techniques to the study of photophosphorylation and the unique features of ph...
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A computer model comprising light reactions in PS II and PS I, electron-proton transport reactions in mesophyll and bundle sheath chloroplasts, all enzymatic reactions and most of the known regulatory functions of NADP-ME type C4 photosynthesis has been developed as a system of differential budget equations for intermediate compounds. Rate-equation...
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Various C3,C3-C4 Flaveria Species were examined for their light-dependent ability to concentrate inorganic carbon (CO2 plus HCO3-) within leaf discs. The five C4 species concentrated 14-32 nmol of inorganic carbon per mg Chl (after reaching saturation with 14CO2). Among the 10 C3-C4 species examined, six species showed a considerable capacity to co...
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The photosynthetic efficiency of the CO(2)-concentrating mechanism in two forms of single-cell C(4) photosynthesis in the family Chenopodiaceae was characterized. The Bienertioid-type single-cell C(4) uses peripheral and central cytoplasmic compartments (Bienertia sinuspersici), while the Borszczowioid single-cell C(4) uses distal and proximal comp...
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The husk surrounding the ear of corn/maize (Zea mays) has widely spaced veins with a number of interveinal mesophyll (M) cells and has been described as operating a partial C(3) photosynthetic pathway, in contrast to its leaves, which use the C(4) photosynthetic pathway. Here, we characterized photosynthesis in maize husk and leaf by measuring comb...
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Bienertia sinuspersici is one of only three higher land plant species known to perform C 4 photosynthesis without Kranz anatomy through partitioning of photosynthetic functions between dimorphic chloroplasts in a single photosynthetic cell. We recently reported the successful separation of the two chloroplast types, and biochemical and functional a...
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To study the developmental transition of chloroplasts from C(3) to C(4) photosynthesis in the terrestrial single-cell C(4) species Bienertia sinuspersici, a regeneration protocol was developed. Stem explant material developed callus either with or without red nodular structures (RNS) when cultured on Murashige-Skoog (MS) salts and vitamins, supplem...
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Bienertia sinuspersici is a land plant known to perform C(4) photosynthesis through the location of dimorphic chloroplasts in separate cytoplasmic domains within a single photosynthetic cell. A protocol was developed with isolated protoplasts to obtain peripheral chloroplasts (P-CP), a central compartment (CC), and chloroplasts from the CC (C-CP) t...
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Genus Suaeda (family Chenopodiaceae, subfamily Suaedoideae) has two structural types of Kranz anatomy consisting of a single compound Kranz unit enclosing vascular tissue. One, represented by Suaeda taxifolia, has mesophyll (M) and bundle sheath (BS) cells distributed around the leaf periphery. The second, represented by Suaeda eltonica, has M and...
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Cleomaceae is one of 19 angiosperm families in which C(4) photosynthesis has been reported. The aim of the study was to determine the type, and diversity, of structural and functional forms of C(4) in genus Cleome. Methods Plants of Cleome species were grown from seeds, and leaves were subjected to carbon isotope analysis, light and scanning electr...
Chapter
Plants identified as having C4 photosynthesis have a C4 metabolic cycle with phosphoenolpyruvate carboxylase as the initial catalyst for fixation of atmospheric CO2, and a C4 acid decarboxylase (NADP-malic enzyme, NAD-malic enzyme, or phosphoenolpyruvate carboxykinase), which releases CO2 for fixation by the C3 cycle. Effective donation of CO2 to R...
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Recent research on the photosynthetic mechanisms of plant species in the Chenopodiaceae family revealed that three species, including Bienertia sinuspersici, can carry out C(4) photosynthesis within individual photosynthetic cells, through the development of two cytoplasmic domains having dimorphic chloroplasts. These unusual single-cell C(4) speci...
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Photosynthetic pathway innovations have had a large impact on patterns of diversification of angiosperm lineages and the biogeographic distribution of ecological assemblages. C₄ photosynthesis has been one of the most studied processes in plants with respect to function, structure, occurrence, and response to climatic conditions. One of the most pr...
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In this study we present the functional characterisation of SKD1 (suppressor of K(+) transport growth defect) in salt tolerance of higher plants. SKD1 participates in endosome-mediated protein sorting and expression of SKD1 is salt-induced in Na(+) storage cells of halophyte ice plant. Transgenic Arabidopsis with reduced SKD1 expression were genera...
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Regulation of light harvesting in response to changes in light intensity, CO2 and O2 concentration was studied in C4 species representing three different metabolic subtypes: Sorghum bicolor (NADP-malic enzyme), Amaranthus edulis (NAD-malic enzyme), and Panicum texanum (PEP-carboxykinase). Several photosynthetic parameters were measured on the intac...
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Portulacaceae is one of 19 families of terrestrial plants in which species having C4 photosynthesis have been found. Representative species from major clades of the genus Portulaca were studied to characterize the forms of photosynthesis structurally and biochemically. The species P. amilis, P. grandiflora, P. molokiniensis, P. oleracea, P. pilosa,...
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While malate and fumarate participate in a multiplicity of pathways in plant metabolism, the function of these organic acids as carbon stores in C(3) plants has not been deeply addressed. Here, Arabidopsis (Arabidopsis thaliana) plants overexpressing a maize (Zea mays) plastidic NADP-malic enzyme (MEm plants) were used to analyze the consequences o...
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Bienertia sinuspersici Akhani represents one form of C4 photosynthesis that occurs without Kranz anatomy in family Chenopodiaceae. Analysis of transcript profiles and proteomics were made to gain information on this single-cell C4 photosynthetic mechanism. Chlorenchyma cells were isolated and purified from mature leaves. From these cells, a cDNA li...
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The objective of this study was to characterise photosynthesis in terrestrial non-Kranz (NK) C4 species, Bienertia sinuspersici Akhani and Suaeda aralocaspica (Bunge) Freitag Schtze (formerly Borszczowia aralocaspica), compared with closely related Kranz type C4 Suaeda eltonica Iljin and Suaeda taxifolia Standley, and C3 species Suaeda heterophylla...