Faculty Opinions recommendation of Proof of C4 photosynthesis without Kranz anatomy in Bienertia cycloptera (Chenopodiaceae).

Leaf anatomy characteristics provide important evidences about the transition between C3 and C4 pathways. The C4 photosynthesis pathway allowed to reduce the C3 photorespiratory rate, concentrating CO2 around the Rubisco site and using structures and machinery already presented in C3 plants. In monocots, it is observed a high number of C4 lineages, most of them phylogenetically related to C3 groups. The genus Apochloa (C3), subtribe Arthropogoninae, is related to two C4 genera Coleataenia and Cyphonanthus. The aim of this study was to evaluate four Apochloa species in order to establish anatomical characteristics related to the evolution of C4 pathway in this group. By means of transverse sections fully expanded leaves of A. euprepes, A. lorea, A. molinioides, and A. poliophylla were collected and the characteristics of the mesophyll (M) and bundle sheath (BS) cells were determined. These species showed a rustic Kranz anatomy with enlarged and radial arranged BS cells, which have few organelles organized in a centrifugal position. Although the modifications of BS cells are probably related to the maintenance of plant water status, we also discuss the evolution for the establishment of C4 photosynthesis in the related C4 genera.

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C4 photosynthesis in terrestrial plants does not require Kranz anatomy

Trends in Plant Science ◽

10.1016/s1360-1385(02)02293-8 ◽

2002 ◽

Vol 7 (7) ◽

pp. 283-285 ◽

Cited By ~ 40

Author(s):

Rowan F Sage

Keyword(s):

C4 Photosynthesis ◽

Terrestrial Plants ◽

Kranz Anatomy

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Challenges and Approaches to Crop Improvement Through C3-to-C4 Engineering

Frontiers in Plant Science ◽

10.3389/fpls.2021.715391 ◽

2021 ◽

Vol 12 ◽

Author(s):

Hongchang Cui

Keyword(s):

Photosynthetic Efficiency ◽

C4 Photosynthesis ◽

Crop Improvement ◽

Bundle Sheath ◽

C4 Plants ◽

System Level ◽

C3 Plants ◽

World Population ◽

Kranz Anatomy ◽

The Past

With a rapidly growing world population and dwindling natural resources, we are now facing the enormous challenge of increasing crop yields while simultaneously improving the efficiency of resource utilization. Introduction of C4 photosynthesis into C3 crops is widely accepted as a key strategy to meet this challenge because C4 plants are more efficient than C3 plants in photosynthesis and resource usage, particularly in hot climates, where the potential for productivity is high. Lending support to the feasibility of this C3-to-C4 engineering, evidence indicates that C4 photosynthesis has evolved from C3 photosynthesis in multiple lineages. Nevertheless, C3-to-C4 engineering is not an easy task, as several features essential to C4 photosynthesis must be introduced into C3 plants. One such feature is the spatial separation of the two phases of photosynthesis (CO2 fixation and carbohydrate synthesis) into the mesophyll and bundle sheath cells, respectively. Another feature is the Kranz anatomy, characterized by a close association between the mesophyll and bundle sheath (BS) cells (1:1 ratio). These anatomical features, along with a C4-specific carbon fixation enzyme (PEPC), form a CO2-concentration mechanism that ensures a high photosynthetic efficiency. Much effort has been taken in the past to introduce the C4 mechanism into C3 plants, but none of these attempts has met with success, which is in my opinion due to a lack of system-level understanding and manipulation of the C3 and C4 pathways. As a prerequisite for the C3-to-C4 engineering, I propose that not only the mechanisms that control the Kranz anatomy and cell-type-specific expression in C3 and C4 plants must be elucidated, but also a good understanding of the gene regulatory network underlying C3 and C4 photosynthesis must be achieved. In this review, I first describe the past and current efforts to increase photosynthetic efficiency in C3 plants and their limitations; I then discuss a systems approach to tackling down this challenge, some practical issues, and recent technical innovations that would help us to solve these problems.

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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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Changes in the plasmodesma structure and permeability at the bundle sheath and mesophyll interface during the maize C4 leaf development

10.1101/2020.09.30.320283 ◽

2020 ◽

Author(s):

Peng Gao ◽

Baijuan Du ◽

Pinghua Li ◽

Byung-Ho Kang

Keyword(s):

Cell Wall ◽

Organic Acids ◽

Molecular Diffusion ◽

C4 Photosynthesis ◽

Solute Concentration ◽

Bundle Sheath ◽

Solute Diffusion ◽

Cell Wall Modification ◽

Maize Leaf ◽

Kranz Anatomy

AbstractPlasmodesmata are intercellular channels that facilitate molecular diffusion between neighboring plant cells. The development and functions of plasmodesmata are controlled by multiple intra- and intercellular signaling pathways. Plasmodesmata are critical for dual-cell C4 photosynthesis in maize because plasmodesmata at the mesophyll and bundle sheath interface mediate exchange of CO2-carrying organic acids. We examined developmental profiles of plasmodesmata and chloroplasts in the maize leaf from young cells in the base to mature cell in the tip using microscopy approaches. Young mesophyll and bundle sheath cells in the leaf base had proplastids, and their plasmodesmata were simple, devoid of cytoplasmic sleeves. In maturing cells where Kranz anatomy and dimorphic chloroplasts were evident, we observed extensive remodeling of plasmodesmata that included acquisition of an electron-dense ring on the mesophyll side and cytoplasmic sleeves on the bundle sheath side. Interestingly, the changes in plasmodesmata involved a drop in symplastic dye mobility and suberin accumulation in the cell wall, implying a more stringent mesophyll-bundle sheath transport. We compared kinetics of the plasmodesmata and the cell wall modification in wildtype leaves with leaves from ppdk and dct2 mutants with defective C4 pathways. Plasmodesmata development, symplastic transport inhibition, and cell wall suberization were accelerated in the mutant lines, probably due to the aberrant C4 cycle. Transcriptomic analyses of the mutants confirmed the expedited changes in the cell wall. Our results suggest that a regulatory machinery at the mesophyll-bundle sheath boundary suppresses erroneous flux of C4 metabolites in the maize leaf.Significance StatementPlasmodesmata in the maize Kranz anatomy mediate the exchange of organic acids between mesophyll and bundle sheath. Since solute diffusion through plasmodesmata is governed by solute concentration gradients, a balanced distribution of C4 metabolites is critical for concentration of CO2 in the bundle sheath. Plasmodesmata bridging the mesophyll and bundle sheath cytoplasm have a cylindrical cavity, which can facilitate molecular movements, and a valve-like attachment. Construction of the sophisticated plasmodesmata was linked to C4 photosynthesis, and plasmodesmata assembly finished more rapidly in maize mutants with defective C4 pathways than in wild-type plants. These results suggest that the specialized plasmodesmata contribute to controlled transport of C4 metabolites.

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C4 mechanisms in aquatic angiosperms: comparisons with terrestrial C4 systems

Functional Plant Biology ◽

10.1071/pp01219 ◽

2002 ◽

Vol 29 (3) ◽

pp. 379 ◽

Cited By ~ 74

Author(s):

George Bowes ◽

Srinath K. Rao ◽

Gonzalo M. Estavillo ◽

Julia B. Reiskind

Keyword(s):

C4 Photosynthesis ◽

Hydrilla Verticillata ◽

Terrestrial Plants ◽

Relative Growth ◽

Kranz Anatomy ◽

Low Co2 ◽

C4 Species ◽

Internal Co2 ◽

Photosynthesis Regulation ◽

Marine Macroalga

Aquatic C4 photosynthesis probably arose in response to dissolved CO2 limitations, possibly before its advent in terrestrial plants. Of over 7600 C4 species, only about a dozen aquatic species are identified. Amphibious Eleocharis species (sedges) have C3–C4 photosynthesis and Kranz anatomy in aerial, but not submersed, leaves. Aquatic grasses have aerial and submersed leaves with C4 or C3–C4 photosynthesis and Kranz anatomy, but some lack Kranz anatomy in the submersed leaves. Two freshwater submersed monocots, Hydrilla verticillata and possibly Egeria densa, are C4 NADP-malic enzyme (NADP-ME) species. A marine macroalga, Udotea flabellum (Chlorophyta), and possibly a diatom, are C4, so it is not confined to angiosperms. Submersed C4 species differ from terrestrial in that β-carboxylation is cytosolic with chloroplastic decarboxylation and Rubisco carboxylation, so the C4 and Calvin cycles operate in the same cell without Kranz anatomy. Unlike terrestrial plants, Hydrilla is a facultative C4 that shifts from C3 to C4 in low [CO2]. It is well documented, with C4 gas exchange and pulse-chase characteristics, enzyme kinetics and localization, high internal [CO2], relative growth rate, and quantum yield studies. It has multiple phosphoenolpyruvate carboxylase isoforms with C3-like sequences. Hvpepc4 appears to be the photosynthetic form induced in C4 leaves, but it differs from terrestrial C4 isoforms in lacking a C4 signature Serine. The molecular mass of NADP-ME (72 kDa) also resembles a C3 isoform. Hydrilla belongs to the ancient Hydrocharitaceae family, and gives insight to early C4 development. Hydrilla is an excellent ‘minimalist’ system to study C4 photosynthesis regulation without anatomical complexities.

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Occurrence and evolutionary inferences about Kranz anatomy in Cyperaceae (Poales)

Anais da Academia Brasileira de Ciências ◽

10.1590/0001-3765201520150175 ◽

2015 ◽

Vol 87 (4) ◽

pp. 2177-2188 ◽

Cited By ~ 2

Author(s):

SHIRLEY MARTINS ◽

MARCCUS ALVES ◽

VERA L. SCATENA

Keyword(s):

C4 Photosynthesis ◽

Structural Characteristics ◽

Aquatic Environments ◽

Phylogenetic Groups ◽

Environmental Pressures ◽

Kranz Anatomy ◽

The Family ◽

Different Types ◽

Diverse Origin ◽

Potential Origin

ABSTRACT Cyperaceae is an angiosperm family with the greatest diversity of species with Kranz anatomy. Four different types of Kranz anatomy (chlorocyperoid, eleocharoid, fimbristyloid and rhynchosporoid) have been described for this angiosperm family, and the occurrence and structural characteristics of these types are important to trace evolutionary hypotheses. The purpose of this study was to examine the available data on Cyperaceae Kranz anatomy, emphasizing taxonomy, geographic distribution, habitat and anatomy, to infer the potential origin of the Kranz anatomy in this family. The results showed that the four types of Kranz anatomy (associated with C4 photosynthesis) in Cyperaceae emerged numerous times in unrelated phylogenetic groups. However, the convergence of these anatomical types, except rhynchosporoid, was observed in certain groups. Thus, the diverse origin of these species might result from different environmental pressures that promote photorespiration. Greater variation in occurrence of Kranz anatomy and anatomical types was observed inEleocharis, whose emergence of the C4 pathway was recent compared with other genera in the family, and the species of this genus are located in aquatic environments.

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