Are crassulacean acid metabolism and C4 photosynthesis incompatible?

2002 ◽  
Vol 29 (6) ◽  
pp. 775 ◽  
Author(s):  
Rowan F. Sage
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
C4 Photosynthesis ◽  
Bundle Sheath ◽  
C4 Plants ◽  
Cam Plants ◽  
Bundle Sheath Cells ◽  
C4 Pathway ◽  
Cam Species ◽  
Cam Photosynthesis

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. Despite sharing a similar metabolism, crassulacean acid metabolism (CAM) and C4 photosynthesis are not known to occur in identical species, with the exception of Portulaca spp. In Portulaca, C4 and weak CAM photosynthesis occur in distinct regions of the leaf, rather than in the same cells. This is in marked contrast to the situation in most CAM species where C3 and CAM photosynthesis are active in the same cell over the course of a day and growing season. The lack of CAM and C4 photosynthesis in identical cells of a plant indicates these photosynthetic pathways are incompatible. Incompatibilities between CAM and C4 photosynthesis could have a number of biochemical, anatomical and evolutionary explanations. Biochemical incompatibilities could result from the requirement for spatial separation of C3 and C4 phases in C4 plants versus temporal separation in CAM plants. In C4 plants, regulatory systems coordinate mesophyll and bundle sheath metabolism, with light intensity being the major environmental signal. In CAM plants, a circadian oscillator coordinates day and night phases of CAM. The requirement for rapid intercellular transport in C4 plants may be incompatible with the intracellular transport and storage needs of CAM. For example, the large vacuole required for malate storage in CAM could impede metabolite diffusion between mesophyll and bundle sheath cells in C4 plants. Anatomical barriers could also exist because both CAM and the C4 pathway require distinct leaf anatomies for efficient function. Efficient function of the C4 pathway generally requires an outer layer of cells specialized for phosphoenolpyruvate (PEP) carboxylation and regeneration and an inner layer for CO2 accumulation and refixation, while CAM species require enlarged vacuoles and tight cell packing. In evolutionary terms, barriers preventing CAM and C4 photosynthesis in the same species may be the initial steps in the respective evolutionary pathways from C3 ancestors. The first steps in C4 photosynthesis are related to scavenging photorespiratory CO2 via localization of glycine decarboxylase in the bundle sheath cells. The initial steps in CAM evolution are associated with the scavenging of respiratory CO2 at night by PEP carboxylation. In each, simplified versions of the specialized anatomy may need to be present for the evolutionary sequence to begin. For C4 evolution, enhanced bundle sheath size may be required in C3 ancestors; for CAM evolution, succulence may be required. Thus, before CAM or C4 photosynthesis began to evolve, the outcome of the evolutionary experiment may have been predetermined.

scholarly journals A perspective on crassulacean acid metabolism photosynthesis evolution of orchids on different continents: Dendrobium as a case study

2019 ◽  
Vol 70 (22) ◽  
pp. 6611-6619
Author(s):  
Ming-He Li ◽  
Ding-Kun Liu ◽  
Guo-Qiang Zhang ◽  
Hua Deng ◽  
Xiong-De Tu ◽  
...  
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Middle Miocene ◽  
Acid Metabolism ◽  
Flowering Plants ◽  
Asian Clade ◽  
Wide Range ◽  
Cam Species ◽  
Climatic Cooling ◽  
Cam Photosynthesis

Abstract Members of the Orchidaceae, one of the largest families of flowering plants, evolved the crassulacean acid metabolism (CAM) photosynthesis strategy. It is thought that CAM triggers adaptive radiation into new niche spaces, yet very little is known about its origin and diversification on different continents. Here, we assess the prevalence of CAM in Dendrobium, which is one of the largest genera of flowering plants and found in a wide range of environments, from the high altitudes of the Himalayas to relatively arid habitats in Australia. Based on phylogenetic time trees, we estimated that CAM, as determined by δ 13C values less negative than –20.0‰, evolved independently at least eight times in Dendrobium. The oldest lineage appeared in the Asian clade during the middle Miocene, indicating the origin of CAM was associated with a pronounced climatic cooling that followed a period of aridity. Divergence of the four CAM lineages in the Asian clade appeared to be earlier than divergence of those in the Australasian clade. However, CAM species in the Asian clade are much less diverse (25.6%) than those in the Australasian clade (57.9%). These findings shed new light on CAM evolutionary history and the aridity levels of the paleoclimate on different continents.

scholarly journals Improving Light Use Efficiency in C4 Plants by Increasing Electron Transport Rate

Proceedings ◽  
2020 ◽  
Vol 36 (1) ◽  
pp. 203
Author(s):  
Maria Ermakova ◽  
Robert T. Furbank ◽  
Susanne von Caemmerer
Keyword(s):  
Electron Transport ◽  
Conversion Efficiency ◽  
C4 Photosynthesis ◽  
Foxtail Millet ◽  
Bundle Sheath ◽  
C4 Plants ◽  
Crop Species ◽  
Bundle Sheath Cells ◽  
Light Conversion Efficiency ◽  
Sheath Cells

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.

scholarly journals Altered Gene Regulatory Networks are Associated with the Transition from C3 to Crassulacean Acid Metabolism in Erycina (Oncidiinae: Orchidaceae)

2018 ◽  
Author(s):  
Karolina Heyduk ◽  
Michelle Hwang ◽  
Victor A. Albert ◽  
Katia Silvera ◽  
Tianying Lan ◽  
...  
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Regulatory Networks ◽  
Acid Metabolism ◽  
Network Connectivity ◽  
Gene Families ◽  
Multiple Time ◽  
Photosynthetic Pathway ◽  
Cam Plants ◽  
Multiple Time Points ◽  
Cam Photosynthesis

AbstractCrassulacean acid metabolism (CAM) photosynthesis is a modification of the core C3 photosynthetic pathway that improves the ability of plants to assimilate carbon in water-limited environments. CAM plants fix CO2 mostly at night, when transpiration rates are low. All of the CAM pathway genes exist in ancestral C3 species, but the timing and magnitude of expression are greatly altered between C3 and CAM species. Understanding these regulatory changes is key to elucidating the mechanism by which CAM evolved from C3. Here we use two closely related species in the Orchidaceae, Erycina pusilla (CAM) and Erycina crista-galli (C3), to conduct comparative transcriptomic analyses across multiple time points. Clustering of genes with expression variation across the diel cycle revealed some canonical CAM pathway genes similarly expressed in both species, regardless of photosynthetic pathway. However, gene network construction indicated that 149 gene families had significant differences in network connectivity and were further explored for these functional enrichments. Genes involved in light sensing and ABA signaling were some of the most differently connected genes between the C3 and CAM Erycina species, in agreement with the contrasting diel patterns of stomatal conductance in C3 and CAM plants. Our results suggest changes to transcriptional cascades are important for the transition from C3 to CAM photosynthesis in Erycina.

scholarly journals Exploring the Relationship between Crassulacean Acid Metabolism (CAM) and Mineral Nutrition with a Special Focus on Nitrogen

2019 ◽  
Vol 20 (18) ◽  
pp. 4363 ◽  
Author(s):  
Paula Natália Pereira ◽  
John C. Cushman
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Nutrient Availability ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Special Focus ◽  
Cam Plants ◽  
Use Efficiency ◽  
Cam Species ◽  
The Relationship

Crassulacean acid metabolism (CAM) is characterized by nocturnal CO2 uptake and concentration, reduced photorespiration, and increased water-use efficiency (WUE) when compared to C3 and C4 plants. Plants can perform different types of CAM and the magnitude and duration of CAM expression can change based upon several abiotic conditions, including nutrient availability. Here, we summarize the abiotic factors that are associated with an increase in CAM expression with an emphasis on the relationship between CAM photosynthesis and nutrient availability, with particular focus on nitrogen, phosphorus, potassium, and calcium. Additionally, we examine nitrogen uptake and assimilation as this macronutrient has received the greatest amount of attention in studies using CAM species. We also discuss the preference of CAM species for different organic and inorganic sources of nitrogen, including nitrate, ammonium, glutamine, and urea. Lastly, we make recommendations for future research areas to better understand the relationship between macronutrients and CAM and how their interaction might improve nutrient and water-use efficiency in order to increase the growth and yield of CAM plants, especially CAM crops that may become increasingly important as global climate change continues.

scholarly journals Phosphorylation of phosphoenolpyruvate carboxykinase in plants. Studies in plants with C4 photosynthesis and Crassulacean acid metabolism and in germinating seeds

1996 ◽  
Vol 317 (3) ◽  
pp. 653-658 ◽  
Author(s):  
Robert P. WALKER ◽  
Richard C. LEEGOOD
Keyword(s):  
Molecular Mass ◽  
Crassulacean Acid Metabolism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Acid Metabolism ◽  
C4 Photosynthesis ◽  
C4 Grasses ◽  
Cam Plants ◽  
Sds Page ◽  
Germinating Seeds

We have previously shown that phosphoenolpyruvate carboxykinase (PEPCK) is phosphorylated in vivo in the cotyledons of darkened cucumber seedlings and that phosphorylation is reversed by light [Walker and Leegood (1995) FEBS Lett. 362, 70–74]. In this study the molecular mass of PEPCK was estimated in a range of gluconeogenic seedlings and in leaves of C4 plants and plants with Crassulacean acid metabolism (CAM). Phosphorylation of PEPCK was studied in these plants by feeding tissues with [32P]Pi and assessing phosphorylation by SDS/PAGE and autoradiography of either total proteins or of immunoprecipitated protein. In gluconeogenic seedlings and most CAM plants PEPCK had a molecular mass of 74 kDa, whereas in C4 grasses the molecular mass of PEPCK was always smaller and varied from 67–71 kDa. In all gluconeogenic seedlings and leaves of CAM plants PEPCK was phosphorylated, but it was not phosphorylated in all species of C4 grasses studied. In CAM plants, phosphorylation of PEPCK occurred at night and dephosphorylation occurred during the day. In C4 grasses phosphorylation occurred when leaves were darkened and the enzyme was dephosphorylated following illumination, but it was only phosphorylated in those plants with larger (71 kDa) molecular mass forms of PEPCK.

Functional leaf anatomy of plants with crassulacean acid metabolism

2005 ◽  
Vol 32 (5) ◽  
pp. 409 ◽  
Author(s):  
Elizabeth A. Nelson ◽  
Tammy L. Sage ◽  
Rowan F. Sage
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Internal Resistance ◽  
C3 Plants ◽  
Cam Plants ◽  
Internal Co2 ◽  
Low Exposure ◽  
Cam Species ◽  
Diffusional Barrier ◽  
Carbon Economy

Crassulacean acid metabolism (CAM) has evolved independently on dozens of occasions and is now found in over 7% of plant species. In this study, the leaf structure of a phylogenetically diverse assemblage of 18 CAM plants was compared with six C3 plants and four C4 plants to assess whether consistent anatomical patterns that may reflect functional constraints are present. CAM plants exhibited increased cell size and increased leaf and mesophyll thickness relative to C3 and C4 species. CAM species also exhibited reduced intercellular air space (IAS) and reduced length of mesophyll surface exposed to IAS per unit area (Lmes / area). The low volume of IAS and low exposure of mesophyll surface to IAS likely increases internal resistance to CO2 in CAM tissues. While this diffusional barrier may limit uptake of CO2 during Phases II and IV, carbon economy could be enhanced through the reduced loss of internal CO2 during all four phases of CAM.

scholarly journals The role of cis-elements in the evolution of crassulacean acid metabolism photosynthesis

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Li-Yu Chen ◽  
Yinghui Xin ◽  
Ching Man Wai ◽  
Juan Liu ◽  
Ray Ming
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Global Climate ◽  
Regulatory Elements ◽  
Promoter Regions ◽  
Leaf Tissues ◽  
Cam Species ◽  
Cam Photosynthesis ◽  
Selection Of

AbstractCrassulacean acid metabolism (CAM) photosynthesis is an innovation of carbon concentrating mechanism that is characterized by nocturnal CO2 fixation. Recent progresses in genomics, transcriptomics, proteomics, and metabolomics of CAM species yielded new knowledge and abundant genomic resources. In this review, we will discuss the pattern of cis-elements in stomata movement-related genes and CAM CO2 fixation genes, and analyze the expression dynamic of CAM related genes in green leaf tissues. We propose that CAM photosynthesis evolved through the re-organization of existing enzymes and associated membrane transporters in central metabolism and stomatal movement-related genes, at least in part by selection of existing circadian clock cis-regulatory elements in their promoter regions. Better understanding of CAM evolution will help us to design crops that can thrive in arid or semi-arid regions, which are likely to expand due to global climate change.

Estimation of diffusive resistance of bundle sheath cells to CO2 from modeling of C4 photosynthesis

1996 ◽  
Vol 49 (3) ◽  
pp. 195-208 ◽  
Author(s):  
Dongxiang He ◽  
Gerald E. Edwards
Keyword(s):  
C4 Photosynthesis ◽  
Bundle Sheath ◽  
Diffusive Resistance ◽  
Bundle Sheath Cells ◽  
Sheath Cells
Sign in / Sign up

Export Citation Format

Share Document