Biochemical and Structural Diversification of C Photosynthesis in Tribe Zoysieae (Poaceae).

C photosynthesis has evolved independently multiple times in grass lineages with nine anatomical and three biochemical subtypes. Chloridoideae represents one of the separate events and contains species of two biochemical subtypes, NAD-ME and PEP-CK. Assessment of C photosynthesis diversification is limited by species sampling.

Structural diversity in salt excreting glands and salinity tolerance in Oryza coarctata, Sporobolus anglicus and Urochondra setulosa.

Unlike the bicellular glands characteristic of all known excreting grasses, unique single-celled salt glands were discovered in the only salt tolerant species of the genus Oryza, Oryza coarctata. Salt tolerance has evolved frequently in a large number of grass lineages with distinct difference in mechanisms. Mechanisms of salt tolerance were studied in three species of grasses characterized by salt excretion: C wild rice species Oryza coarctata, and C species Sporobolus anglicus and Urochondra setulosa.

Diversity in structure and forms of carbon assimilation in photosynthetic organs in Cleome (Cleomaceae).

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.

Unique photosynthetic phenotypes in Portulaca (Portulacaceae): C3-C4 intermediates and NAD-ME C4 species with Pilosoid-type Kranz anatomy.

Portulacaceae is a family that has considerable diversity in photosynthetic phenotypes. It is one of 19 families of terrestrial plants where species having C photosynthesis have been found. Most species in Portulaca are in the alternate-leaved (AL) lineage, which includes one clade (Cryptopetala) with taxa lacking C photosynthesis and three clades having C species (Oleracea, Umbraticola and Pilosa).

The unique structural and biochemical development of single cell C4 photosynthesis along longitudinal leaf gradients in Bienertia sinuspersici and Suaeda aralocaspica (Chenopodiaceae).

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 domains. In the C4-C domain, C4 acids are formed in the C4 cycle during capture of atmospheric CO2 by phosphoenolpyruvate carboxylase. In the C4-D domain, CO2 released in the C4 cycle via mitochondrial NAD-malic enzyme is refixed by Rubisco.

An assessment of the capacity for phosphoenolpyruvate carboxykinase to contribute to C4 photosynthesis.

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, recently PEPCK has been reported to function in C4 photosynthesis in eudicot species including Cleome gynandra (Cleomaceae), Trianthema portulacastrum and Zaleya pentandra (Aizoaceae).

The acclimation of photosynthesis and respiration to temperature in the C3 -C4 intermediate Salsola divaricata: induction of high respiratory CO2 release under low temperature.

Photosynthesis in C(3) -C(4) intermediates reduces carbon loss by photorespiration through refixing photorespired CO(2) within bundle sheath cells. This is beneficial under warm temperatures where rates of photorespiration are high; however, it is unknown how photosynthesis in C(3) -C(4) plants acclimates to growth under cold conditions. Therefore, the cold tolerance of the C(3) -C(4) Salsola divaricata was tested to determine whether it reverts to C(3) photosynthesis when grown under low temperatures.

Differentiation of C4 photosynthesis along a leaf developmental gradient in two Cleome species having different forms of Kranz anatomy.

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.

Evolution of leaf anatomy and photosynthetic pathways in Portulacaceae.

Premise Of The Study: 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 Portulacaceae.

Structural and physiological analyses in Salsoleae (Chenopodiaceae) indicate multiple transitions among C3, intermediate, and C4 photosynthesis.

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 photosynthetic features were analysed on selected species of Salsola which are not performing C4 based on leaf carbon isotope composition. The results infer the following progression in distinct functional and structural forms from C3 to intermediate to C4 photosynthesis with increased leaf succulence without changes in vein density: From species performing C3 photosynthesis with Sympegmoid anatomy with two equivalent layers of elongated M cells, with few organelles in a discontinuous layer of bundle sheath (BS) cells (S.

Functional analysis of corn husk photosynthesis.

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 combined gas exchange and carbon isotope discrimination, the oxygen dependence of the CO(2) compensation point, and photosynthetic enzyme activity and localization together with anatomy. The CO(2) assimilation rate in the husk was less than that in the leaves and did not saturate at high CO(2), indicating CO(2) diffusion limitations.

Development of structural and biochemical characteristics of C(4) photosynthesis in two types of Kranz anatomy in genus Suaeda (family Chenopodiaceae).

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 BS surrounding vascular bundles in the central plane.

Diversity in forms of C4 in the genus Cleome (Cleomaceae).

Background And Aims: 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 electron microscopy, western blot analysis of proteins, and in situ immunolocalization for ribulose bisphosphate carboxylase oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC).

Revealing diversity in structural and biochemical forms of C4 photosynthesis and a C3-C4 intermediate in genus Portulaca L. (Portulacaceae).

Portulacaceae is one of 19 families of terrestrial plants in which species having C(4) 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.

Analysis of Arabidopsis with highly reduced levels of malate and fumarate sheds light on the role of these organic acids as storage carbon molecules.

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 of sustained low malate and fumarate levels on the physiology of this C(3) plant. When grown in short days (sd), MEm plants developed a pale-green phenotype with decreased biomass and increased specific leaf area, with thin leaves having lower photosynthetic performance.

Photosynthetic features of non-Kranz type C versus Kranz type C and C species in subfamily Suaedoideae (Chenopodiaceae).

The objective of this study was to characterise photosynthesis in terrestrial non-Kranz (NK) C species, Bienertia sinuspersici Akhani and Suaeda aralocaspica (Bunge) Freitag & Schütze (formerly Borszczowia aralocaspica), compared with closely related Kranz type C Suaeda eltonica Iljin and Suaeda taxifolia Standley, and C species Suaeda heterophylla Bunge and Suaeda maritima Dumort in subfamily Suaedoideae (Chenopodiaceae). Traditional Kranz type C photosynthesis has several advantages over C photosynthesis under certain environmental conditions by suppressing photorespiration. The different photosynthetic types were evaluated under varying levels of CO and light at 25°C.

Diversity in leaf anatomy, and stomatal distribution and conductance, between salt marsh and freshwater species in the C(4) genus Spartina (Poaceae).

Leaf anatomy, stomatal density, and leaf conductance were studied in 10 species of Spartina (Poaceae) from low versus high salt marsh, and freshwater habitats. Internal structure, external morphology, cuticle structure, and stomatal densities were studied with light and electron microscopy. Functional significance of leaf structure was examined by measures of CO(2) uptake and stomatal distributions.

Structural, biochemical, and physiological characterization of photosynthesis in two C4 subspecies of Tecticornia indica and the C3 species Tecticornia pergranulata (Chenopodiaceae).

Among dicotyledon families, Chenopodiaceae has the most C(4) species and the greatest diversity in structural forms of C(4). In subfamily Salicornioideae, C(4) photosynthesis has, so far, only been found in the genus Halosarcia which is now included in the broadly circumscribed Tecticornia. Comparative anatomical, cytochemical, and physiological studies on these taxa, which have near-aphyllous photosynthetic shoots, show that T.

Physiological, anatomical and biochemical characterisation of photosynthetic types in genus Cleome (Cleomaceae).

C photosynthesis has evolved many times in 18 different families of land plants with great variation in leaf anatomy, ranging from various forms of Kranz anatomy to C photosynthesis occurring within a single type of photosynthetic cell. There has been little research on photosynthetic typing in the family Cleomaceae, in which only one C species has been identified, Cleome gynandra L. There is recent interest in selecting and developing a C species from the family Cleomaceae as a model C system, since it is the most closely related to Arabidopsis, a C model system (Brown et al.

Functional characterization of phosphoenolpyruvate carboxykinase-type C4 leaf anatomy: immuno-, cytochemical and ultrastructural analyses.

Background And Aims: Species having C4 photosynthesis belonging to the phosphoenolpyruvate carboxykinase (PEP-CK) subtype, which are found only in family Poaceae, have the most complex biochemistry among the three C4 subtypes. In this study, biochemical (western blots and immunolocalization of some key photosynthetic enzymes) and structural analyses were made on several species to further understand the PEP-CK system. This included PEP-CK-type C4 species Urochloa texana (subfamily Panicoideae), Spartina alterniflora and S.

Differentiation of cellular and biochemical features of the single-cell C4 syndrome during leaf development in Bienertia cycloptera (Chenopodiaceae).

The terrestrial plant Bienertia cycloptera has been shown to accomplish C(4) photosynthesis within individual chlorenchyma cells by spatially separating the phases of carbon assimilation into distinct peripheral and central compartments. In this study, anatomical, physiological, and biochemical techniques were used to determine how this unique compartmentation develops. Western blots show ribulose-1,5-bisphosphate carboxylase (Rubisco) (chloroplastic) is present in the youngest leaves and increases during development, while levels of C(4) enzymes-pyruvate,Pi dikinase (chloroplastic), phosphoenolpyruvate carboxylase (PEPC) (cytosol), and NAD-malic enzyme (mitochondrial)-increase later in development.

Functional compartmentation of C photosynthesis in the triple layered chlorenchyma of Aristida (Poaceae).

The genus Aristida (Poaceae), is composed of species that have Kranz anatomy and C photosynthesis. Kranz anatomy typically consists of two photosynthetic cell types: a layer of mesophyll cells where atmospheric CO is fixed into C acids, and an internal, chlorenchymatous vascular bundle sheath to which C acids are transferred and then decarboxylated to donate CO to the C cycle. The anatomy of Aristida species is unusual as it has three distinct layers of chlorenchyma cells surrounding the vascular tissue: an inner bundle sheath, an outer bundle sheath and the mesophyll cells.

Single-cell C(4) photosynthesis versus the dual-cell (Kranz) paradigm.

The efficiency of photosynthetic carbon assimilation in higher plants faces significant limitations due to the oxygenase activity of the enzyme Rubisco, particularly under warmer temperatures or water stress. A drop in atmospheric CO(2) and rise in O(2) as early as 300 mya provided selective pressure for the evolution of mechanisms to concentrate CO(2) around Rubisco in order to minimize oxygenase activity and the resultant loss of carbon through photorespiration. It is well established that a carbon-concentrating mechanism occurs in some terrestrial plants through the process of C(4) photosynthesis.

Light-dependent development of single cell C4 photosynthesis in cotyledons of Borszczowia aralocaspica (Chenopodiaceae) during transformation from a storage to a photosynthetic organ.

Background And Aims: Previous work has shown that Borszczowia aralocaspica (Chenopodiaceae) accomplishes C4 photosynthesis in a unique, polarized single-cell system in leaves. Mature cotyledons have the same structure as leaves, with chlorenchyma cells having biochemical polarization of dimorphic chloroplasts and C4 functions at opposite ends of the cell.

Key Results: Development of the single-celled C4 syndrome in cotyledons was characterized.

Development of biochemical specialization and organelle partitioning in the single-cell C4 system in leaves of Borszczowia aralocaspica (Chenopodiaceae).

The terrestrial plant Borszczowia aralocaspica (Chenopodiaceae) has recently been shown to contain the entire C(4) photosynthesis mechanism within individual, structurally and biochemically polarized chlorenchyma cells rather than in a dual cell system, as has been the paradigm for this type of carbon fixation (Nature 414: 543-546, 2001). Analysis of carbon isotope composition and (14)CO(2) fixation shows that photosynthesis and growth of B. aralocaspica occurs through carbon acquired by C(4) photosynthesis.