The CO2 Concentrating Mechanism of C4 Photosynthesis: Bundle Sheath Cell CO2 Concentration and Leakage

1997 ◽  
Vol 24 (4) ◽  
pp. 543 ◽  
Author(s):  
Colin L. D. Jenkins
Keyword(s):  
C4 Photosynthesis ◽  
Direct Methods ◽  
Net Photosynthesis ◽  
Co2 Concentration ◽  
Bundle Sheath ◽  
Central Importance ◽  
Rubisco Activity ◽  
Mesophyll Cells ◽  
Net Photosynthesis Rate ◽  
Oxygenase Activity

The C4 acid cycle functions in C4 photosynthesis to concentrate CO2 in bundle sheath (BS) cells, thereby minimising oxygenase activity of Rubisco and associated photorespiration. Some key features of this process are reviewed here. During steady-state photosynthesis, the CO2 concentration maintained in BS cells must be a compromise since, at the higher levels required to prevent photorespiration, the potential for CO2 leakage from BS cells would be increased. Despite its central importance in C4 photosynthesis, it has not been possible to precisely determine the BS CO2 concentration. Leakage requires that the C4 cycle rate exceeds the net photosynthesis rate and lowers the efficiency of the overall process. Leakage of CO2 from the BS has been estimated by a number of indirect and, recently, by more direct methods. In a simulation, simple relationships between Rubisco activity, photorespiration, and leakage were calculated at increasing BS CO2 concentrations. From this, and determined values for leakage, the likely concentration of CO2 in BS cells may be 10–20-fold greater than in mesophyll cells. Higher concentrations would have little further effect on oxygenase activity.

scholarly journals Bundle-sheath leakiness in C4 photosynthesis: a careful balancing act between CO2 concentration and assimilation

2014 ◽  
Vol 65 (13) ◽  
pp. 3443-3457 ◽  
Author(s):  
J. Kromdijk ◽  
N. Ubierna ◽  
A. B. Cousins ◽  
H. Griffiths
Keyword(s):  
C4 Photosynthesis ◽  
Co2 Concentration ◽  
Bundle Sheath

scholarly journals Developmental Effects on Relative Use of PEPCK and NADP-ME Pathways of C4 Photosynthesis in Maize

2021 ◽  
Author(s):  
Jennifer J Arp ◽  
Shrikaar Kambhampati ◽  
Kevin Chu ◽  
Somnath Koley ◽  
Lauren M Jenkins ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Leaf Development ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Photosynthesis ◽  
Leaf Age ◽  
Bundle Sheath ◽  
Decarboxylase Activity ◽  
Mesophyll Cells ◽  
Source To Sink ◽  
Canopy Position

C4 photosynthesis is an adaptive photosynthetic pathway which concentrates CO2 around Rubisco in specialized bundle sheath cells to reduce photorespiration. Historically, the pathway has been characterized into three different subtypes based on the decarboxylase involved, although recent work has provided evidence that some plants can use multiple decarboxylases, with maize in particular using both the NADP-malic enzyme (NADP-ME) pathway and phosphoenolpyruvate carboxykinase (PEPCK) pathway. Parallel C4 pathways could be advantageous in balancing energy and reducing equivalents between bundle sheath and mesophyll cells, in decreasing the size of the metabolite gradients between cells and may better accommodate changing environmental conditions or source to sink demands on growth. The enzyme activity of C4 decarboxylases can fluctuate with different stages of leaf development, but it remains unclear if the pathway flexibility is an innate aspect of leaf development or an adaptation to the leaf microenvironment that is regulated by the plant. In this study, variation in the two C4 pathways in maize were characterized at nine plant ages throughout the life cycle. Two positions in the canopy were examined for variation in physiology, gene expression, metabolite concentration, and enzyme activity, with particular interest in asparagine as a potential regulator of C4 decarboxylase activity. Variation in C4 and C3 metabolism was observed for both leaf age and canopy position, reflecting the ability of C4 pathways to adapt to changing microenvironments.

scholarly journals C4 photosynthesis with Kranz anatomy evolved in the Oryza coarctata Roxb

2020 ◽  
Author(s):  
Soni Chowrasia ◽  
Tapan Kumar Mondal
Keyword(s):  
C4 Photosynthesis ◽  
Expression Patterns ◽  
Bundle Sheath ◽  
Ultrastructural Observation ◽  
Mesophyll Cells ◽  
Potential Donor ◽  
Kranz Anatomy ◽  
Vein Density ◽  
Bundle Sheath Cells ◽  
Sheath Cells

AbstractThe C4 cycle is a complex biochemical pathway that has been evolved in plants to deal with the adverse environmental conditions. Mostly C4 plants grow in arid, water-logged area or poor nutrient habitats. Wild species, Oryza coarctata (genome type KKLL; chromosome number (4x) =48, genome size 665 Mb) belongs to the genus of Oryza which thrives well under high saline as well as submerged conditions. Here, we report for the first time that O. coarctata is a C4 plant by observing the increased biomass growth, morphological features such as vein density, anatomical features including ultrastuctural characteristics as well as expression patterns of C4 related genes. Leaves of O. coarctata have higher vein density and possess Kranz anatomy. The ultrastructural observation showed chloroplast dimorphism i.e. presence of agranal chloroplasts in bundle sheath cells whereas, mesophyll cells contain granal chloroplasts. The cell walls of bundle sheath cells contain tangential suberin lamella. The transcript level of C4 specific genes such as phosphoenolpyruvate carboxylase, pyruvate orthophosphate dikinase, NADP-dependent malic enzyme and malate dehydrogenase was higher in leaves of O. coarctata compare to high yielding rice cultivar (IR-29). These anatomical, ultra structural as well as molecular changes in O. coarctata for C4 photosynthesis adaptation might be might be due to its survival in wide diverse condition from aquatic to saline submerged condition. Being in the genus of Oryza, this plant could be potential donor for production of C4 rice in future through conventional breeding, as successful cross with rice has already been reported.

Functional compartmentation of C4 photosynthesis in the triple layered chlorenchyma of Aristida (Poaceae)

2005 ◽  
Vol 32 (1) ◽  
pp. 67 ◽  
Author(s):  
Elena V. Voznesenskaya ◽  
Simon D. X. Chuong ◽  
Nuria K. Koteyeva ◽  
Gerald E. Edwards ◽  
Vincent R. Franceschi
Keyword(s):  
Vascular Tissue ◽  
C4 Photosynthesis ◽  
Cell Types ◽  
Bundle Sheath ◽  
Mesophyll Cells ◽  
Western Blots ◽  
Kranz Anatomy ◽  
Bundle Sheath Cells ◽  
Low Levels ◽  
And Function

The genus Aristida (Poaceae), is composed of species that have Kranz anatomy and C4 photosynthesis. Kranz anatomy typically consists of two photosynthetic cell types: a layer of mesophyll cells where atmospheric CO2 is fixed into C4 acids, and an internal, chlorenchymatous vascular bundle sheath to which C4 acids are transferred and then decarboxylated to donate CO2 to the C3 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. In this study of Aristida purpurea Nutt. var. longiseta, the functions of the three layers of chlorenchyma cells relative to the C4 photosynthetic mechanism were determined using ultrastructural analysis, western blots, immunolocalisation of photosynthetic enzymes and starch histochemistry. The results indicate that mesophyll cells contain high levels of phosphoenolpyruvate carboxylase (PEPC) and pyruvate Pi dikinase (PPDK), and function to capture CO2 in the C4 cycle. The inner bundle sheath, which is high in Rubisco and contains NADP-malic enzyme and glycine decarboxylase, functions to transfer CO2 to the C3 cycle through decarboxylation of C4 acids and by decarboxylation of glycine in the glycolate pathway. The outer chlorenchymatous sheath is where ADPG pyrophosphorylase is mainly located, and this cell layer functions as the primary site of starch storage. The outer sheath, which has low levels of Rubisco and PEPC, may also have a role in refixation of any CO2 that leaks from the inner bundle sheath cells.

scholarly journals Four Mutant Alleles Elucidate the Role of the G2 Protein in the Development of C4 and C3 Photosynthesizing Maize Tissues

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 787-797
Author(s):  
Lizzie Cribb ◽  
Lisa N Hall ◽  
Jane A Langdale
Keyword(s):  
Cell Types ◽  
Bundle Sheath ◽  
Primary Role ◽  
Ribulose Bisphosphate Carboxylase ◽  
Sheath Cell ◽  
Mesophyll Cells ◽  
Phenotypic Data ◽  
Bisphosphate Carboxylase ◽  
Bundle Sheath Cell

Abstract Maize leaf blades differentiate dimorphic photosynthetic cell types, the bundle sheath and mesophyll, between which the reactions of C4 photosynthesis are partitioned. Leaf-like organs of maize such as husk leaves, however, develop a C3 pattern of differentiation whereby ribulose bisphosphate carboxylase (RuBPCase) accumulates in all photosynthetic cell types. The Golden2 (G2) gene has previously been shown to play a role in bundle sheath cell differentiation in C4 leaf blades and to play a less well-defined role in C3 maize tissues. To further analyze G2 gene function in maize, four g2 mutations have been characterized. Three of these mutations were induced by the transposable element Spm. In g2-bsd1-m1 and g2-bsd1-s1, the element is inserted in the second intron and in g2-pg14 the element is inserted in the promoter. In the fourth case, g2-R, four amino acid changes and premature polyadenylation of the G2 transcript are observed. The phenotypes conditioned by these four mutations demonstrate that the primary role of G2 in C4 leaf blades is to promote bundle sheath cell chloroplast development. C4 photosynthetic enzymes can accumulate in both bundle sheath and mesophyll cells in the absence of G2. In C3 tissue, however, G2 influences both chloroplast differentiation and photosynthetic enzyme accumulation patterns. On the basis of the phenotypic data obtained, a model that postulates how G2 acts to facilitate C4 and C3 patterns of tissue development is proposed.

scholarly journals Light and CO2 Modulate the Accumulation and Localization of Phenolic Compounds in Barley Leaves

Antioxidants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 385
Author(s):  
Lena Hunt ◽  
Karel Klem ◽  
Zuzana Lhotáková ◽  
Stanislav Vosolsobě ◽  
Michal Oravec ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Phenolic Compounds ◽  
Co2 Concentration ◽  
Environmental Stressors ◽  
Low Light ◽  
Mesophyll Cells ◽  
Stress Prevention ◽  
Tolerant Variety ◽  
Barley Leaves

Barley (Hordeum vulgare) accumulates phenolic compounds (PhCs), which play a key role in plant defense against environmental stressors as antioxidants or UV screening compounds. The influence of light and atmospheric CO2 concentration ([CO2]) on the accumulation and localization of PhCs in barley leaves was examined for two varieties with different tolerances to oxidative stress. PhC localization was visualized in vivo using fluorescence microscopy. Close relationships were found between fluorescence-determined localization of PhCs in barley leaves and PhC content estimated using liquid chromatography coupled with mass spectroscopy detection. Light intensity had the strongest effect on the accumulation of PhCs, but the total PhC content was similar at elevated [CO2], minimizing the differences between high and low light. PhCs localized preferentially near the surfaces of leaves, but under low light, an increasing allocation of PhCs in deeper mesophyll layers was observed. The PhC profile was significantly different between barley varieties. The relatively tolerant variety accumulated significantly more hydroxycinnamic acids, indicating that these PhCs may play a more prominent role in oxidative stress prevention. Our research presents novel evidence that [CO2] modulates the accumulation of PhCs in barley leaves. Mesophyll cells, rather than epidermal cells, were most responsive to environmental stimuli in terms of PhC accumulation.

scholarly journals Transmission of Engineered Plastids in Sugarcane, a C4 Monocotyledonous Plant, Reveals that Sorting of Preprogrammed Progenitor Cells Produce Heteroplasmy

Plants ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 26
Author(s):  
Ghulam Mustafa ◽  
Muhammad Sarwar Khan
Keyword(s):  
Progenitor Cells ◽  
Plastid Transformation ◽  
Bundle Sheath ◽  
Homologous Sequence ◽  
Regeneration System ◽  
Mesophyll Cells ◽  
Transgenic Sugarcane ◽  
Bundle Sheath Cells ◽  
Dicotyledonous Plants ◽  
Species Specific

We report here plastid transformation in sugarcane using biolistic transformation and embryogenesis-based regeneration approaches. Somatic embryos were developed from unfurled leaf sections, containing preprogrammed progenitor cells, to recover transformation events on antibiotic-containing regeneration medium. After developing a proficient regeneration system, the FLARE-S (fluorescent antibiotic resistance enzyme, spectinomycin and streptomycin) expression cassette that carries species-specific homologous sequence tails was used to transform plastids and track gene transmission and expression in sugarcane. Plants regenerated from streptomycin-resistant and genetically confirmed shoots were subjected to visual detection of the fluorescent enzyme using a fluorescent stereomicroscope, after genetic confirmation. The resultant heteroplasmic shoots remained to segregate on streptomycin-containing MS medium, referring to the unique pattern of division and sorting of cells in C4 monocotyledonous compared to C3 monocotyledonous and dicotyledonous plants since in sugarcane bundle sheath and mesophyll cells are distinct and sort independently after division. Hence, the transformation of either mesophyll or bundle sheath cells will develop heteroplasmic transgenic plants, suggesting the transformation of both types of cells. Whilst developed transgenic sugarcane plants are heteroplasmic, and selection-based regeneration protocol envisaging the role of division and sorting of cells in the purification of transplastomic demands further improvement, the study has established many parameters that may open up exciting possibilities to express genes of agricultural or pharmaceutical importance in sugarcane.

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