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Joseph A M Holtum - One of the best experts on this subject based on the ideXlab platform.
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constitutive and facultative Crassulacean Acid Metabolism cam in cuban oregano coleus amboinicus lamiaceae
2021Co-Authors: Klaus Winter, Joseph A M Holtum, Aurelio Virgo, Jorge Aranda, Milton N GarciaAbstract:Plants exhibiting the water-conserving Crassulacean Acid Metabolism (CAM) photosynthetic pathway provide some of the most intriguing examples of photosynthetic diversity and plasticity. Here, a largely unnoticed facet of CAM-plant photosynthesis is highlighted: the co-occurrence of ontogenetically controlled constitutive and environmentally controlled facultative CAM in a species. Both forms of CAM are displayed in leaves of Coleus amboinicus Lour. (Lamiaceae), a semi-succulent perennial plant with oregano-like flavour that is native to southern and eastern Africa and naturalised elsewhere in the tropics. Under well-watered conditions, leaves assimilate CO2 predominantly by the C3 pathway. They also display low levels of CO2 uptake at night accompanied by small nocturnal increases in leaf tissue Acidity. This indicates the presence of weakly expressed constitutive CAM. CAM expression is strongly enhanced in response to drought stress. The drought-enhanced component of CAM is reversible upon rewatering and thus considered to be facultative. In contrast to C. amboinicus, the thin-leaved closely related Coleus scutellarioides (L.) Benth. exhibits net CO2 fixation solely in the light via the C3 pathway, both under well-watered and drought conditions. However, low levels of nocturnal Acidification detected in leaves and stems indicate that the CAM cycle is present. The highly speciose mint family, which contains few known CAM-exhibiting species and is composed predominantly of C3 species, appears to be an excellent group of plants for studying the evolutionary origins of CAM and for determining the position of facultative CAM along the C3–full CAM trajectory.
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facultative Crassulacean Acid Metabolism in a c3 c4 intermediate
2019Co-Authors: Klaus Winter, Joseph A M Holtum, Erika J Edwards, Rowan F Sage, Aurelio VirgoAbstract:The Portulacaceae enable the study of the evolutionary relationship between C4 and Crassulacean Acid Metabolism (CAM) photosynthesis. Shoots of well-watered plants of the C3-C4 intermediate species Portulaca cryptopetala Speg. exhibit net uptake of CO2 solely during the light. CO2 fixation is primarily via the C3 pathway as indicated by a strong stimulation of CO2 uptake when shoots were provided with air containing 2% O2. When plants were subjected to water stress, daytime CO2 uptake was reduced and CAM-type net CO2 uptake in the dark occurred. This was accompanied by nocturnal accumulation of Acid in both leaves and stems, also a defining characteristic of CAM. Following rewatering, net CO2 uptake in the dark ceased in shoots, as did nocturnal Acidification of the leaves and stems. With this unequivocal demonstration of stress-related reversible, i.e. facultative, induction of CAM, P. cryptopetala becomes the first C3-C4 intermediate species reported to exhibit CAM. Portulaca molokiniensis Hobdy, a C4 species, also exhibited CAM only when subjected to water stress. Facultative CAM has now been demonstrated in all investigated species of Portulaca, which are well sampled from across the phylogeny. This strongly suggests that in Portulaca, a lineage in which species engage predominately in C4 photosynthesis, facultative CAM is ancestral to C4. In a broader context, it has now been demonstrated that CAM can co-exist in leaves that exhibit any of the other types of photosynthesis known in terrestrial plants: C3, C4 and C3-C4 intermediate.
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Crassulacean Acid Metabolism in the Basellaceae (Caryophyllales).
2018Co-Authors: Joseph A M Holtum, Erika J Edwards, Lillian P. Hancock, Klaus WinterAbstract:C4 and Crassulacean Acid Metabolism (CAM) have evolved in the order Caryophyllales many times but neither C4 nor CAM have been recorded for the Basellaceae, a small family in the CAM-rich sub-order Portulacineae. 24 h gas exchange and day-night changes in titratable Acidity were measured in leaves of Anredera baselloides exposed to wet-dry-wet cycles. While net CO2 uptake was restricted to the light period in well-watered plants, net CO2 fixation in the dark, accompanied by significant nocturnal increases in leaf Acidity, developed in droughted plants. Plants reverted to solely C3 photosynthesis upon rewatering. The reversible induction of nocturnal net CO2 uptake by drought stress indicates that this species is able to exhibit CAM in a facultative manner. This is the first report of CAM in a member of the Basellaceae.
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facultative Crassulacean Acid Metabolism cam in four small c3 and c4 leaf succulents
2017Co-Authors: Klaus Winter, Joseph A M HoltumAbstract:Measurements of whole-plant gas exchange and titratable Acidity demonstrate that the Australian native species Anacampseros australiana J.M.Black (Anacampserotaceae), Crassula sieberiana (Schult. & Schult.f.) Druce (Crassulaceae) and Portulaca australis Endl. (Portulacaceae) and the widespread naturalised tropical exotic, Portulaca pilosa L., exhibit facultative Crassulacean Acid Metabolism (CAM). In well-watered plants, net CO2 uptake was restricted to the daylight hours and occurred via the C-3 pathway (A. australiana and C. sieberiana) or the C-4 pathway (P. australis and P. pilosa). Leaves of well-watered plants did not accumulate titratable Acidity during the night. Following drought treatment, CO2 uptake in the light by shoots decreased markedly, nocturnal gas-exchange shifted from net CO2 loss to a CAM-type pattern that included net CO2 uptake, and leaves Acidified at night. Nocturnal CO2 uptake by shoots and leaf Acidification were most pronounced in A. australiana and least so in C. sieberiana. The induction of dark CO2 uptake and tissue Acidification was fully reversible in all four species: upon rewatering, nocturnal CO2 uptake and Acidification ceased and the rates of CO2 incorporation in the light were restored. Wesuggest that, hitherto considered relatively exceptional globally, facultative CAM may be more common than previously suspected, particularly among the generally small ephemeral leaf-succulents that characterise Australia's succulent flora.
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australia lacks stem succulents but is it depauperate in plants with Crassulacean Acid Metabolism cam
2016Co-Authors: Joseph A M Holtum, Darren M Crayn, Erika J Edwards, Lillian P. Hancock, Rowan F Sage, Michael D Crisp, Klaus WinterAbstract:In the flora of Australia, the driest vegetated continent, Crassulacean Acid Metabolism (CAM), the most water-use efficient form of photosynthesis, is documented in only 0.6% of native species. Most are epiphytes and only seven terrestrial. However, much of Australia is unsurveyed, and carbon isotope signature, commonly used to assess photosynthetic pathway diversity, does not distinguish between plants with low-levels of CAM and C3 plants. We provide the first census of CAM for the Australian flora and suggest that the real frequency of CAM in the flora is double that currently known, with the number of terrestrial CAM species probably 10-fold greater. Still unresolved is the question why the large stem-succulent life — form is absent from the native Australian flora even though exotic large cacti have successfully invaded and established in Australia.
Howard Griffiths - One of the best experts on this subject based on the ideXlab platform.
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model approaches to advance Crassulacean Acid Metabolism system integration
2020Co-Authors: Methawi Chomthong, Howard GriffithsAbstract:This review summarises recent progress in understanding Crassulacean Acid Metabolism (CAM) systems and the integration of internal and external stimuli to maximise water-use efficiency. Complex CAM traits have been reduced to their minimum and captured as computational models, which can now be refined using recently available data from transgenic manipulations and large-scale omics studies. We identify three key areas in which an appropriate choice of modelling tool could help capture relevant comparative molecular data to address the evolutionary drivers and plasticity of CAM. One focus is to identify the environmental and internal signals that drive inverse stomatal opening at night. Secondly, it is important to identify the regulatory processes required to orchestrate the diel pattern of carbon fluxes within mesophyll layers. Finally, the limitations imposed by contrasting succulent systems and associated hydraulic conductance components should be compared in the context of water-use and evolutionary strategies. While network analysis of transcriptomic data can provide insights via co-expression modules and hubs, alternative forms of computational modelling should be used iteratively to define the physiological significance of key components and informing targeted functional gene manipulation studies. We conclude that the resultant improvements of bottom-up, mechanistic modelling systems can enhance progress towards capturing the physiological controls for phylogenetically diverse CAM systems in the face of the recent surge of information in this omics era.
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Crassulacean Acid Metabolism cam offers sustainable bioenergy production and resilience to climate change
2016Co-Authors: Nick A Owen, K F Fahy, Howard GriffithsAbstract:Biomass production on low-grade land is needed to meet future energy demands and minimize resource conflicts. This, however, requires improvements in plant water-use efficiency (WUE) that are beyond conventional C3 and C4 dedicated bioenergy crops. Here we present the first global-scale geographic information system (GIS)-based productivity model of two highly water-efficient Crassulacean Acid Metabolism (CAM) candidates: Agave tequilana and Opuntia ficus-indica. Features of these plants that translate to WUE advantages over C3 and C4 bioenergy crops include nocturnal stomatal opening, rapid rectifier-like root hydraulic conductivity responses to fluctuating soil water potential and the capacity to buffer against periods of drought. Yield simulations for the year 2070 were performed under the four representative concentration pathway (RCPs) scenarios presented in the IPCC’s 5th Assessment Report. Simulations on low-grade land suggest that O. ficus-indica alone has the capacity to meet ‘extreme’ bioenergy demand scenarios (>600 EJ yr � 1 ) and is highly resilient to climate change (� 1%). Agave tequilana is moderately impacted (� 11%). These results are significant because bioenergy demand scenarios >600 EJ yr � 1 could be met without significantly increasing conflicts with food production and contributing to deforestation. Both CAM candidates outperformed the C4 bioenergy crop, Panicum virgatum L. (switchgrass) in arid zones in the latitudinal range 30°S–30°N.
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eddy covariance captures four phase Crassulacean Acid Metabolism cam gas exchange signature in agave
2016Co-Authors: Nick A Owen, Howard Griffiths, Jamie Males, Orlaith Ni Choncubhair, Jose Ignacio Del Real Laborde, Ramon Rubiocortes, Gary LaniganAbstract:Mass and energy fluxes were measured over a field of Agave tequilana in Mexico using eddy covariance (EC) methodology. Data were gathered over 252 d, including the transition from wet to dry periods. Net ecosystem exchanges (FN,EC ) displayed a Crassulacean Acid Metabolism (CAM) rhythm that alternated from CO2 sink at night to CO2 source during the day, and partitioned canopy fluxes (FA,EC ) showed a characteristic four-phase CO2 exchange pattern. Results were cross-validated against diel changes in titratable Acidity, leaf-unfurling rates, energy exchange fluxes and reported biomass yields. Projected carbon balance (g C m(-2) year(-1) , mean ± 95% confidence interval) indicated the site was a net sink of -333 ± 24, of which contributions from soil respiration were +692 ± 7, and FA,EC was -1025 ± 25. EC estimated biomass yield was 20.1 Mg (dry) ha(-1) year(-1) . Average integrated daily FA,EC was -234 ± 5 mmol CO2 m(-2) d(-1) and persisted almost unchanged after 70 d of drought conditions. Regression analyses were performed on the EC data to identify the best environmental predictors of FA . Results suggest that the carbon acquisition strategy of Agave offers productivity and drought resilience advantages over conventional semi-arid C3 and C4 bioenergy candidates.
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a system dynamics model integrating physiology and biochemical regulation predicts extent of Crassulacean Acid Metabolism cam phases
2013Co-Authors: Nick A Owen, Howard GriffithsAbstract:Summary A system dynamics (SD) approach was taken to model Crassulacean Acid Metabolism (CAM) expression from measured biochemical and physiological constants. SD emphasizes state-dependent feedback interaction to describe the emergent properties of a complex system. These mechanisms maintain biological systems with homeostatic limits on a temporal basis. Previous empirical studies on CAM have correlated biological constants (e.g. enzyme kinetic parameters) with expression over the CAM diel cycle. The SD model integrates these constants within the architecture of the CAM ‘system’. This allowed quantitative causal connections to be established between biological inputs and the four distinct phases of CAM delineated by gas exchange and malic Acid accumulation traits. Regulation at flow junctions (e.g. stomatal and mesophyll conductance, and malic Acid transport across the tonoplast) that are subject to feedback control (e.g. stomatal aperture, malic Acid inhibition of phosphoenolpyruvate carboxylase, and enzyme kinetics) was simulated. Simulated expression for the leaf-succulent Kalanchoe daigremontiana and more succulent tissues of Agave tequilana showed strong correlation with measured gas exchange and malic Acid accumulation (R2 = 0.912 and 0.937, respectively, for K. daigremontiana and R2 = 0.928 and 0.942, respectively, for A. tequilana). Sensitivity analyses were conducted to quantitatively identify determinants of diel CO2 uptake. The transition in CAM expression from low to high volume/area tissues (elimination of phase II–IV carbon-uptake signatures) was achieved largely by the manipulation three input parameters.
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exploiting the potential of plants with Crassulacean Acid Metabolism for bioenergy production on marginal lands
2009Co-Authors: Anne M Borland, Howard Griffiths, James Hartwell, Andrew J C SmithAbstract:Crassulacean Acid Metabolism (CAM) is a photosynthetic adaptation that facilitates the uptake of CO(2) at night and thereby optimizes the water-use efficiency of carbon assimilation in plants growing in arid habitats. A number of CAM species have been exploited agronomically in marginal habitats, displaying annual above-ground productivities comparable with those of the most water-use efficient C(3) or C(4) crops but with only 20% of the water required for cultivation. Such attributes highlight the potential of CAM plants for carbon sequestration and as feed stocks for bioenergy production on marginal and degraded lands. This review highlights the metabolic and morphological features of CAM that contribute towards high biomass production in water-limited environments. The temporal separation of carboxylation processes that underpins CAM provides flexibility for modulating carbon gain over the day and night, and poses fundamental questions in terms of circadian control of Metabolism, growth, and productivity. The advantages conferred by a high water-storage capacitance, which translate into an ability to buffer fluctuations in environmental water availability, must be traded against diffusive (stomatal plus internal) constraints imposed by succulent CAM tissues on CO(2) supply to the cellular sites of carbon assimilation. The practicalities for maximizing CAM biomass and carbon sequestration need to be informed by underlying molecular, physiological, and ecological processes. Recent progress in developing genetic models for CAM are outlined and discussed in light of the need to achieve a systems-level understanding that spans the molecular controls over the pathway through to the agronomic performance of CAM and provision of ecosystem services on marginal lands.
Klaus Winter - One of the best experts on this subject based on the ideXlab platform.
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evolution of Crassulacean Acid Metabolism cam as an escape from ecological niche conservatism in malagasy bulbophyllum orchidaceae
2021Co-Authors: Alexander Gamisch, Klaus Winter, Gunter A Fischer, Hans Peter ComesAbstract:Despite growing evidence that niche shifts are more common in flowering plants than previously thought, little is known of whether such shifts are promoted by changes in photosynthetic pathways. Here we combine the most complete phylogeny for epiphytic Malagasy Bulbophyllum orchids (c. 210 spp.) with climatic niche and carbon isotope ratios to infer the group's spatial-temporal history, and the role of strongly expressed Crassulacean Acid Metabolism (CAM) in facilitating niche shifts and diversification. We find that most extant species still retain niche (Central Highland) and photosynthesis (C3 ) states as present in the single mid-Miocene (c. 12.70 million yr ago (Ma)) ancestor colonizing Madagascar. However, we also infer a major transition to CAM, linked to a late Miocene (c. 7.36 Ma) invasion of species from the sub-humid highland first into the island's humid eastern coastal, and then into the seasonally dry 'Northwest Sambirano' rainforests, yet without significant effect on diversification rates. These findings indicate that CAM in tropical epiphytes may be selectively advantageous even in high rainfall habitats, rather than presenting a mere adaptation to dry environments or epiphytism per se. Overall, our study qualifies CAM as an evolutionary 'gateway' trait that considerably widened the spatial-ecological amplitude of Madagascar's most species-rich orchid genus.
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constitutive and facultative Crassulacean Acid Metabolism cam in cuban oregano coleus amboinicus lamiaceae
2021Co-Authors: Klaus Winter, Joseph A M Holtum, Aurelio Virgo, Jorge Aranda, Milton N GarciaAbstract:Plants exhibiting the water-conserving Crassulacean Acid Metabolism (CAM) photosynthetic pathway provide some of the most intriguing examples of photosynthetic diversity and plasticity. Here, a largely unnoticed facet of CAM-plant photosynthesis is highlighted: the co-occurrence of ontogenetically controlled constitutive and environmentally controlled facultative CAM in a species. Both forms of CAM are displayed in leaves of Coleus amboinicus Lour. (Lamiaceae), a semi-succulent perennial plant with oregano-like flavour that is native to southern and eastern Africa and naturalised elsewhere in the tropics. Under well-watered conditions, leaves assimilate CO2 predominantly by the C3 pathway. They also display low levels of CO2 uptake at night accompanied by small nocturnal increases in leaf tissue Acidity. This indicates the presence of weakly expressed constitutive CAM. CAM expression is strongly enhanced in response to drought stress. The drought-enhanced component of CAM is reversible upon rewatering and thus considered to be facultative. In contrast to C. amboinicus, the thin-leaved closely related Coleus scutellarioides (L.) Benth. exhibits net CO2 fixation solely in the light via the C3 pathway, both under well-watered and drought conditions. However, low levels of nocturnal Acidification detected in leaves and stems indicate that the CAM cycle is present. The highly speciose mint family, which contains few known CAM-exhibiting species and is composed predominantly of C3 species, appears to be an excellent group of plants for studying the evolutionary origins of CAM and for determining the position of facultative CAM along the C3–full CAM trajectory.
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evolution of Crassulacean Acid Metabolism cam as an escape from ecological niche conservatism in malagasy bulbophyllum orchidaceae
2021Co-Authors: Alexander Gamisch, Klaus Winter, Gunter A Fischer, Hans Peter ComesAbstract:Introductory paragraph Despite growing evidence that niche shifts are more common in flowering plants than previously thought, still little is known about the key physiological (e.g. photosynthesis) traits underlying such niche shifts. To address this question, we here combine a comprehensively sampled phylogeny for mostly epiphytic Malagasy Bulbophyllum orchids (c. 210 spp.) with climatic niche and carbon isotope-derived photosynthesis data to infer the groups’ spatial-temporal history and to test the role of Crassulacean Acid Metabolism (CAM), a highly water-use efficient type of photosynthesis, in facilitating niche shifts and diversification. We find that most extant species still retain niche (Central Highland) and photosynthesis (C3) states as likely present in the single mid-Miocene (c. 12.70 Ma) ancestor colonizing Madagascar. However, we also infer a major transition to CAM, linked to a late Miocene (c. 7.36 Ma) invasion of species from the sub-humid highland niche first into the island’s humid eastern coastal, and then into the seasonally dry ‘Northwest Sambirano’ rainforests, yet without significant effect on diversification rates. These findings support the rarely recognized hypothesis that CAM in tropical epiphytes may be selectively advantageous even in high rainfall habitats, rather than presenting a mere adaptation to dry environments or epiphytism per se. Overall, our study qualifies CAM as an evolutionary ‘gateway’ trait that considerably widened the spatial-ecological amplitude of Madagascar’s most species-rich orchid genus.
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facultative Crassulacean Acid Metabolism in a c3 c4 intermediate
2019Co-Authors: Klaus Winter, Joseph A M Holtum, Erika J Edwards, Rowan F Sage, Aurelio VirgoAbstract:The Portulacaceae enable the study of the evolutionary relationship between C4 and Crassulacean Acid Metabolism (CAM) photosynthesis. Shoots of well-watered plants of the C3-C4 intermediate species Portulaca cryptopetala Speg. exhibit net uptake of CO2 solely during the light. CO2 fixation is primarily via the C3 pathway as indicated by a strong stimulation of CO2 uptake when shoots were provided with air containing 2% O2. When plants were subjected to water stress, daytime CO2 uptake was reduced and CAM-type net CO2 uptake in the dark occurred. This was accompanied by nocturnal accumulation of Acid in both leaves and stems, also a defining characteristic of CAM. Following rewatering, net CO2 uptake in the dark ceased in shoots, as did nocturnal Acidification of the leaves and stems. With this unequivocal demonstration of stress-related reversible, i.e. facultative, induction of CAM, P. cryptopetala becomes the first C3-C4 intermediate species reported to exhibit CAM. Portulaca molokiniensis Hobdy, a C4 species, also exhibited CAM only when subjected to water stress. Facultative CAM has now been demonstrated in all investigated species of Portulaca, which are well sampled from across the phylogeny. This strongly suggests that in Portulaca, a lineage in which species engage predominately in C4 photosynthesis, facultative CAM is ancestral to C4. In a broader context, it has now been demonstrated that CAM can co-exist in leaves that exhibit any of the other types of photosynthesis known in terrestrial plants: C3, C4 and C3-C4 intermediate.
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Crassulacean Acid Metabolism in the Basellaceae (Caryophyllales).
2018Co-Authors: Joseph A M Holtum, Erika J Edwards, Lillian P. Hancock, Klaus WinterAbstract:C4 and Crassulacean Acid Metabolism (CAM) have evolved in the order Caryophyllales many times but neither C4 nor CAM have been recorded for the Basellaceae, a small family in the CAM-rich sub-order Portulacineae. 24 h gas exchange and day-night changes in titratable Acidity were measured in leaves of Anredera baselloides exposed to wet-dry-wet cycles. While net CO2 uptake was restricted to the light period in well-watered plants, net CO2 fixation in the dark, accompanied by significant nocturnal increases in leaf Acidity, developed in droughted plants. Plants reverted to solely C3 photosynthesis upon rewatering. The reversible induction of nocturnal net CO2 uptake by drought stress indicates that this species is able to exhibit CAM in a facultative manner. This is the first report of CAM in a member of the Basellaceae.
Anne M Borland - One of the best experts on this subject based on the ideXlab platform.
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shared expression of Crassulacean Acid Metabolism cam genes pre dates the origin of cam in the genus yucca
2019Co-Authors: Karolina Heyduk, Anne M Borland, Jeremy N Ray, Saaravanaraj Ayyampalayam, Nida Moledina, Scott A Harding, Chungjui Tsai, Jim LeebensmackAbstract:Crassulacean Acid Metabolism (CAM) is a carbon-concentrating mechanism that has evolved numerous times across flowering plants and is thought to be an adaptation to water-limited environments. CAM has been investigated from physiological and biochemical perspectives, but little is known about how plants evolve from C3 to CAM at the genetic or metabolic level. Here we take a comparative approach in analyzing time-course data of C3, CAM, and C3+CAM intermediate Yucca (Asparagaceae) species. RNA samples were collected over a 24 h period from both well-watered and drought-stressed plants, and were clustered based on time-dependent expression patterns. Metabolomic data reveal differences in carbohydrate Metabolism and antioxidant response between the CAM and C3 species, suggesting that changes to metabolic pathways are important for CAM evolution and function. However, all three species share expression profiles of canonical CAM pathway genes, regardless of photosynthetic pathway. Despite differences in transcript and metabolite profiles between the C3 and CAM species, shared time-structured expression of CAM genes in both CAM and C3Yucca species suggests that ancestral expression patterns required for CAM may have pre-dated its origin in Yucca.
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nocturnal expression of Crassulacean Acid Metabolism cam genes predates the origin of cam in the genus yucca
2018Co-Authors: Karolina Heyduk, Anne M Borland, Jeremy N Ray, Saaravanaraj Ayyampalayam, Nida Moledina, Scott A Harding, Chungjui Tsai, Jim LeebensmackAbstract:Crassulacean Acid Metabolism (CAM) is a carbon-concentrating mechanism that has evolved numerous times across flowering plants and is thought to be an adaptation to water limited environments. CAM has been investigated from physiological and biochemical perspectives but little is known about how plants evolve from C 3 to CAM at the genetic or metabolic level. Here we take a comparative approach in analyzing time-course data of C 3 , CAM, and C 3 -CAM intermediate Yucca (Asparagaceae) species. RNA samples were collected over a 24-hour period from both well-watered and drought-stressed plants and were clustered based on time-dependent expression patterns. Metabolomic comparisons of the C 3 and CAM species link gene expression to carbohydrate Metabolism and gene network co-expression analyses revealed compositional and functional changes to networks containing canonical CAM genes. Observed differences in carbohydrate Metabolism and antioxidant response between the CAM and C 3 species reveal alternative sugar and starch degradation pathways, underscoring the need for more comparative metabolomic analyses to understand the evolution of CAM from C 3 . Despite many differences in transcript and metabolite profiles between the C3 and CAM species, shared time-structured expression of CAM genes in the C 3 species suggests ancestral expression patterns required for CAM may have predated its origin in Yucca .
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functional anatomical traits of the photosynthetic organs of plants with Crassulacean Acid Metabolism
2018Co-Authors: Anne M Borland, Alistair Leverett, Natalia Hurtadocastano, Xiaohan YangAbstract:Crassulacean Acid Metabolism (CAM) is a photosynthetic adaptation to water and/or CO2 limited environments that has evolved in 400 genera from 36 families of higher plants. Despite the taxonomic and ecological diversity of CAM, plants with this photosynthetic specialization share a number of common anatomical traits that impinge on the physiological processes underpinning photosynthetic CO2 assimilation and water use. Thick, succulent leaves and/or stems are typical for terrestrial CAM plants. The large cells within these succulent tissues serve to accommodate the overnight vacuolar accumulation of malic Acid that defines CAM and also increase water storage capacity. Significant morphological and anatomical diversity exists among leaf and stem succulents that impact on water-use strategies and thus the predisposition towards CAM. We provide an overview of CAM diversity in terms of leaf and stem anatomy, leaf venation and stomatal patterning. We consider the physiological implications of these anatomical traits in terms of water use and leaf hydraulic properties as well as the impacts on CO2 uptake and carbon gain. We also discuss which anatomical traits are likely to be important determinants for the mode and level of CAM that might be engineered into non-CAM species as a means of improving plant water use efficiency.
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climate resilient agroforestry physiological responses to climate change and engineering of Crassulacean Acid Metabolism cam as a mitigation strategy
2015Co-Authors: Anne M Borland, Xiaohan Yang, James Hartwell, David J Weston, Gerald A Tuskan, Stan D Wullschleger, John C. CushmanAbstract:Global climate change threatens the sustainability of agriculture and agroforestry worldwide through increased heat, drought, surface evaporation and associated soil drying. Exposure of crops and forests to warmer and drier environments will increase leaf:air water vapour-pressure deficits (VPD), and will result in increased drought susceptibility and reduced productivity, not only in arid regions but also in tropical regions with seasonal dry periods. Fast-growing, short-rotation forestry (SRF) bioenergy crops such as poplar (Populus spp.) and willow (Salix spp.) are particularly susceptible to hydraulic failure following drought stress due to their isohydric nature and relatively high stomatal conductance. One approach to sustaining plant productivity is to improve water-use efficiency (WUE) by engineering Crassulacean Acid Metabolism (CAM) into C3 crops. CAM improves WUE by shifting stomatal opening and primary CO2 uptake and fixation to the night-time when leaf:air VPD is low. CAM members of the tree genus Clusia exemplify the compatibility of CAM performance within tree species and highlight CAM as a mechanism to conserve water and maintain carbon uptake during drought conditions. The introduction of bioengineered CAM into SRF bioenergy trees is a potentially viable path to sustaining agroforestry production systems in the face of a globally changing climate.
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light quality modulates metabolic synchronization over the diel phases of Crassulacean Acid Metabolism
2014Co-Authors: Johan Ceusters, Anne M Borland, Tahar Taybi, Mario Frans, Christof Godts, Maurice De ProftAbstract:Temporal compartmentation of carboxylation processes is a defining feature of Crassulacean Acid Metabolism and involves circadian control of key metabolic and transport steps that regulate the supply and demand for carbon over a 24h cycle. Recent insights on the molecular workings of the circadian clock and its connection with environmental inputs raise new questions on the importance of light quality and, by analogy, certain photoreceptors for synchronizing the metabolic components of CAM. The present work tested the hypothesis that optimal coupling of stomatal conductance, net CO2 uptake, and the reciprocal turnover of carbohydrates and organic Acids over the diel CAM cycle requires both blue and red light input signals. Contrasting monochromatic wavelengths of blue, green, and red light (i.e. 475, 530, 630nm) with low fluence rates (10 μmol m–2 s–1) were administered for 16 hours each diel cycle for a total treatment time of 48 hours to the obligate CAM bromeliad, Aechmea ‘Maya’. Of the light treatments imposed, low-fluence blue light was a key determinant in regulating stomatal responses, organic Acid mobilization from the vacuole, and daytime decarboxylation. However, the reciprocal relationship between starch and organic Acid turnover that is typical for CAM was uncoupled under low-fluence blue light. Under low-fluence red or green light, the diel turnover of storage carbohydrates was orchestrated in line with the requirements of CAM, but a consistent delay in Acid consumption at dawn compared with plants under white or low-fluence blue light was noted. Consistent with the acknowledged influences of both red and blue light as input signals for the circadian clock, the data stress the importance of both red and blue-light signalling pathways for synchronizing the metabolic and physiological components of CAM over the day/night cycle.
John C. Cushman - One of the best experts on this subject based on the ideXlab platform.
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understanding trait diversity associated with Crassulacean Acid Metabolism cam
2019Co-Authors: Nicholas A Niechayev, Paula Natalia Pereira, John C. CushmanAbstract:Crassulacean Acid Metabolism (CAM) is a specialized mode of photosynthesis that exploits a temporal CO2 pump with nocturnal CO2 uptake and concentration to reduce photorespiration, improve water-use efficiency (WUE), and optimize the adaptability of plants to climates with seasonal or intermittent water limitations. CAM plants display a plastic continuum in the extent to which species engage in net nocturnal CO2 uptake that ranges from 0 to 100%. CAM plants also display diverse enzyme and organic Acid and carbohydrate storage systems, which likely reflect the multiple, independent evolutionary origins of CAM. CAM is often accompanied by a diverse set of anatomical traits, such as tissue succulence and water-storage and water-capture strategies to attenuate drought. Other co-adaptive traits, such as thick cuticles, epicuticular wax, low stomatal density, high stomatal responsiveness, and shallow rectifier-like roots limit water loss under conditions of water deficit. Recommendations for future research efforts to better explore and understand the diversity of traits associated with CAM and CAM Biodesign efforts are presented.
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climate resilient agroforestry physiological responses to climate change and engineering of Crassulacean Acid Metabolism cam as a mitigation strategy
2015Co-Authors: Anne M Borland, Xiaohan Yang, James Hartwell, David J Weston, Gerald A Tuskan, Stan D Wullschleger, John C. CushmanAbstract:Global climate change threatens the sustainability of agriculture and agroforestry worldwide through increased heat, drought, surface evaporation and associated soil drying. Exposure of crops and forests to warmer and drier environments will increase leaf:air water vapour-pressure deficits (VPD), and will result in increased drought susceptibility and reduced productivity, not only in arid regions but also in tropical regions with seasonal dry periods. Fast-growing, short-rotation forestry (SRF) bioenergy crops such as poplar (Populus spp.) and willow (Salix spp.) are particularly susceptible to hydraulic failure following drought stress due to their isohydric nature and relatively high stomatal conductance. One approach to sustaining plant productivity is to improve water-use efficiency (WUE) by engineering Crassulacean Acid Metabolism (CAM) into C3 crops. CAM improves WUE by shifting stomatal opening and primary CO2 uptake and fixation to the night-time when leaf:air VPD is low. CAM members of the tree genus Clusia exemplify the compatibility of CAM performance within tree species and highlight CAM as a mechanism to conserve water and maintain carbon uptake during drought conditions. The introduction of bioengineered CAM into SRF bioenergy trees is a potentially viable path to sustaining agroforestry production systems in the face of a globally changing climate.
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engineering Crassulacean Acid Metabolism to improve water use efficiency
2014Co-Authors: Anne M Borland, Xiaohan Yang, James Hartwell, David J Weston, Karen Schlauch, Timothy J Tschaplinski, Gerald A Tuskan, John C. CushmanAbstract:Climatic extremes threaten agricultural sustainability worldwide. One approach to increase plant water-use efficiency (WUE) is to introduce Crassulacean Acid Metabolism (CAM) into C3 crops. Such a task requires comprehensive systems-level understanding of the enzymatic and regulatory pathways underpinning this temporal CO2 pump. Here we review the progress that has been made in achieving this goal. Given that CAM arose through multiple independent evolutionary origins, comparative transcriptomics and genomics of taxonomically diverse CAM species are being used to define the genetic ‘parts list’ required to operate the core CAM functional modules of nocturnal carboxylation, diurnal decarboxylation, and inverse stomatal regulation. Engineered CAM offers the potential to sustain plant productivity for food, feed, fiber, and biofuel production in hotter and drier climates.
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the incidence of Crassulacean Acid Metabolism in orchidaceae derived from carbon isotope ratios a checklist of the flora of panama and costa rica
2010Co-Authors: Katia Silvera, John C. Cushman, Louis S Santiago, Klaus WinterAbstract:Leaf carbon stable isotopic composition data for 1002 orchid species representing 61% of the total number of orchid species described for Panama and Costa Rica were obtained from herbarium specimens to survey the occurrence of Crassulacean Acid Metabolism (CAM). Carbon isotopic composition of leaf material showed a bimodal distribution with modes at -28‰, indicating C3 photosynthesis, and at -15‰, indicating pronounced CAM photosynthesis. Strong CAM was present in 9.5% of species and in 31 of 162 genera studied. Twelve of these genera were not previously known to contain species exhibiting CAM. A checklist of orchids of Panama and Costa Rica with their d 13 C values and an updated list of all known orchid genera that possess species with the ability to perform CAM are presented. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163, 194–222.
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Crassulacean Acid Metabolism and epiphytism linked to adaptive radiations in the orchidaceae
2009Co-Authors: Katia Silvera, John C. Cushman, Louis S Santiago, Klaus WinterAbstract:Species of the large family Orchidaceae display a spectacular array of adaptations and rapid speciations that are linked to several innovative features, including specialized pollination syndromes, colonization of epiphytic habitats, and the presence of Crassulacean Acid Metabolism (CAM), a water-conserving photosynthetic pathway. To better understand the role of CAM and epiphytism in the evolutionary expansion of tropical orchids, we sampled leaf carbon isotopic composition of 1,103 species native to Panama and Costa Rica, performed character state reconstruction and phylogenetic trait analysis of CAM and epiphytism, and related strong CAM, present in 10% of species surveyed, to climatic variables and the evolution of epiphytism in tropical regions. Altitude was the most important predictor of photosynthetic pathway when all environmental variables were taken into account, with CAM being most prevalent at low altitudes. By creating integrated orchid trees to reconstruct ancestral character states, we found that C3 photosynthesis is the ancestral state and that CAM has evolved at least 10 independent times with several reversals. A large CAM radiation event within the Epidendroideae, the most species-rich epiphytic clade of any known plant group, is linked to a Tertiary species radiation that originated 65 million years ago. Our study shows that parallel evolution of CAM is present among subfamilies of orchids, and correlated divergence between photosynthetic pathways and epiphytism can be explained by the prevalence of CAM in low-elevation epiphytes and rapid speciation of high-elevation epiphytes in the Neotropics, contributing to the astounding diversity in the Orchidaceae.