Metabolic Regulation of Carbon Flux during C4 Photosynthesis I. Evidence for Parallel CO2 Fixation by Mesophyll and Bundle Sheath Cells in situ

C4 plants play a key role in world agriculture and strategies to manipulate and enhance C4 photosynthesis have the potential for major agricultural impacts. The C4 photosynthetic pathway is a biochemical CO2 concentrating mechanism that requires the coordinated functioning of mesophyll and bundle sheath cells of leaves. Chloroplast electron transport in C4 plants is shared between the two cell types; it provides resources for CO2 fixation therefore underpinning the efficiency of photosynthesis. Using the model monocot C4 species Setaria viridis (green foxtail millet) we demonstrated that the Cytochrome (Cyt) b6f complex regulates the electron transport capacity and thus the rate of CO2 assimilation at high light and saturating CO2. Overexpression of the Cyt b6f in both mesophyll and bundle sheath cells results in a higher electron throughput and allows better light conversion efficiency in both photosystems. Importantly, increased Cyt b6f abundance in leaves provides higher rates of C4 photosynthesis without marked changes in Rubisco or chlorophyll content. Our results demonstrate that increasing the rate of electron transport is a viable strategy for improving the light conversion efficiency in C4 crop species like maize and sorghum.

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In Situ Localization of Nadp-Malic Enzyme in Bundle Sheath Cells and Leaf Carbon Isotope Fractionation in Two C4Grasses

International Journal of Plant Sciences ◽

10.1086/297327 ◽

1996 ◽

Vol 157 (1) ◽

pp. 118-122 ◽

Cited By ~ 2

Author(s):

S. Madhavan ◽

Carlos S. Andreo ◽

Veronica G. Maurino ◽

Marion H. O'Leary

Keyword(s):

Carbon Isotope ◽

Malic Enzyme ◽

Isotope Fractionation ◽

Bundle Sheath ◽

Carbon Isotope Fractionation ◽

Bundle Sheath Cells ◽

Sheath Cells

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C4 photosynthesis with Kranz anatomy evolved in the Oryza coarctata Roxb

10.1101/2020.07.12.199232 ◽

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.

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Aspartate stimulation of malate decarboxylation in Zea mays bundle sheath cells: Possible role in regulation of C4 photosynthesis

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(79)90254-7 ◽

1979 ◽

Vol 86 (4) ◽

pp. 1274-1280 ◽

Cited By ~ 8

Author(s):

K.S.R. Chapman ◽

M.D. Hatch

Keyword(s):

Zea Mays ◽

C4 Photosynthesis ◽

Bundle Sheath ◽

Bundle Sheath Cells ◽

Stimulation Of ◽

Sheath Cells

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Photosynthetic Formation of Glycerate in Isolated Bundle Sheath Cells and Its Metabolism in Mesophyll Cells of the C4 Plant Panicum capillare L

Functional Plant Biology ◽

10.1071/pp9800655 ◽

1980 ◽

Vol 7 (6) ◽

pp. 655 ◽

Cited By ~ 7

Author(s):

H Usuda ◽

GE Edwards

Keyword(s):

Co2 Fixation ◽

Major Product ◽

Pentose Phosphate ◽

Bundle Sheath ◽

Phosphate Esters ◽

O2 Evolution ◽

Mesophyll Cells ◽

Glycerate Kinase ◽

Bundle Sheath Cells ◽

Sheath Cells

In isolated bundle sheath cells of P. capillare, glycerate is a major product of 14CO2 fixation at low bicarbonate concentrations. After 6 min of CO2 fixation at 0.34 mM NaHCO3, about 20% of the labelled products was in glycerate and about 45% in glycine plus serine. Inhibitors of the glycollate pathway prevented incorporation of label into glycerate. After 6 min of CO2 fixation at high bicarbonate concentration (20 mM NaH14CO3), a large percentage of the label was incorporated in phosphate esters, insolubles, and sucrose, and little label was observed in metabolites of the glycollate pathway. The results indicate glycerate is primarily formed through the glycollate pathway in bundle sheath cells rather than through 3-phosphoglycerate phosphatase. Glycerate-dependent oxygen evolution in the light and 14C incorporation into phosphate esters from [1-14C]glycerate was observed with mesophyll chloroplasts and mesophyll protoplasts, respectively, but not with bundle sheath cells. This is consistent with our previously published results that glycerate kinase is localized only in C4 mesophyll chloroplasts. Both isolated bundle sheath cells and mesophyll chloroplasts exhibited 3-phosphoglycerate dependent O2 evolution in the light indicating that the reductive phase of photosynthesis is functional in both cells. The results suggest that, during C4 photosynthesis, glycerate is synthesized by the glycollate pathway in bundle sheath cells and subsequently metabolized in mesophyll cells without direct linkage to the reductive pentose phosphate pathway.

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