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Starch metabolism is linked to plant growth, yet blocking its biosynthesis has species-specific consequences. In a new study, plastidial phosphoglucomutase is knocked out in aspen trees using CRISPR-Cas9, limiting starch production and altering photosynthesis, but growth, bud break and wood production proceed unaffected., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Performing accurate measurements of photosynthetic and respiration rates is vital to a large proportion of plant-based studies. While several commercial systems exist to perform such measurements, few are ideal for whole-plant measurements of small herbaceous plants such as Arabidopsis and none offer the capacity for simultaneous analysis of multiple plants. We, therefore, designed a multi-chamber, computer-controlled, infrared gas analyzer-coupled system for the continuous measurement of gas exchange in whole-plant shoots or rosettes. This system was called ETH Gas Exchange System-1 (EGES-1). We have subsequently expanded the device to accommodate a wider variety of species while providing precise control over environmental parameters. Critically, we have (1) increased the flow rates through each of the eight chambers, (2) introduced a computer-controlled feedback loop for the precise introduction of CO 2 , and (3) added an additional feedback loop for the introduction and control of humidity. The advantages of this new system (EGES-2) are illustrated here in the context of a variety of physiological experiments.

Arabidopsis proton gradient regulation (pgr) mutants have high chlorophyll fluorescence and reduced non-photochemical quenching (NPQ) caused by defects in photosynthetic electron transport. Here, we identify PGR6 as the chloroplast lipid droplet (plastoglobule, PG) kinase ABC1K1 (activity of bc1 complex kinase 1). The members of the ABC1/ADCK/UbiB family of atypical kinases regulate ubiquinone synthesis in bacteria and mitochondria, and impact various metabolic pathways in plant chloroplasts. Here, we demonstrate that abc1k1 has a unique photosynthetic and metabolic phenotype that is distinct from that of the abc1k3 homolog. The abc1k1/pgr6 single mutant is specifically deficient in the electron carrier plastoquinone, as well as in β-carotene and the xanthophyll lutein, and is defective in membrane antioxidant tocopherol metabolism. After 2 days of continuous high light stress, abc1k1/pgr6 plants suffer extensive photosynthetic and metabolic perturbations, strongly affecting carbohydrate metabolism. Remarkably, however, the mutant acclimates to high light after 7 days together with a recovery of carotenoid levels and a drastic alteration in the starch-to-sucrose ratio. Moreover, ABC1K1 behaves as an active kinase and phosphorylates VTE1, a key enzyme of tocopherol (vitamin E) metabolism in vitro. Our results indicate that the ABC1K1 kinase constitutes a new type of regulatory link between photosynthetic activity and chloroplast metabolism., (© 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.)

Drought is expected to become an increasingly important factor limiting tree growth caused by climate change. Two divergent clones of Populus nigra (58-861 and Poli) originating from contrasting environments were subjected to water limitation (WL) to elucidate whether they differ in tolerance to drought, which mechanisms to avoid stress they exhibit and whether drought has an impact on the interactions between roots and shoots. Limiting water availability caused photosynthetic rate and total non-structural carbohydrate (TNC) levels to decrease in 58-861. However, starch-degrading enzyme activity and gene expression were induced in roots, and soluble sugar levels were higher than in well-watered (WW) plants. These data suggest that assimilation and partitioning of carbon to the roots are decreased, resulting in mobilization of stored starch. In contrast, the photosynthetic rate of Poli was reduced only late in the treatment, and carbohydrate levels in WL plants were higher than in WW plants. Superoxide dismutase (SOD) activity and gene expression were higher in Poli than in 58-861, even in WW plants, leading to a higher capacity to defend against oxidative stress.

Summary: In leaves of C4 plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C4 acids in mesophyll (M) cells and subsequent decarboxylation in the bundle sheath (BS). In C4 grasses, proliferation of plasmodesmata between these cell types is thought to increase cell‐to‐cell connectivity to allow efficient metabolite movement. However, it is not known whether C4 dicotyledons also show this enhanced plasmodesmal connectivity and so whether this is a general requirement for C4 photosynthesis is not clear. How M and BS cells in C4 leaves become highly connected is also not known.We investigated these questions using 3D‐ and 2D‐electron microscopy on the C4 dicotyledon Gynandropsis gynandra as well as phylogenetically close C3 relatives.The M–BS interface of C4G. gynandra showed higher plasmodesmal frequency compared with closely related C3 species. Formation of these plasmodesmata was induced by light. Pharmacological agents that perturbed photosynthesis reduced the number of plasmodesmata, but this inhibitory effect could be reversed by the provision of exogenous sucrose.We conclude that enhanced formation of plasmodesmata between M and BS cells is wired to the induction of photosynthesis in C4G. gynandra. [ABSTRACT FROM AUTHOR]

Plastid metabolism is critical in both photoautotrophic and heterotrophic plant cells. In chloroplasts, fructose-1,6-bisphosphate aldolase (FBA) catalyses the formation of both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate within the Calvin–Benson cycle. Three Arabidopsis genes, AtFBA1 – AtFBA3 , encode plastidial isoforms of FBA, but the contribution of each isoform is unknown. Phylogenetic analysis indicates that FBA1 and FBA2 derive from a recently duplicated gene, while FBA3 is a more ancient paralog. fba1 mutants are phenotypically indistinguishable from the wild type, while both fba2 and fba3 have reduced growth. We show that FBA2 is the major isoform in leaves, contributing most of the measurable activity. Partial redundancy with FBA1 allows both single mutants to survive, but combining both mutations is lethal, indicating a block of photoautotrophy. In contrast, FBA3 is expressed predominantly in heterotrophic tissues, especially the leaf and root vasculature, but not in the leaf mesophyll. We show that the loss of FBA3 affects plastidial glycolytic metabolism of the root, potentially limiting the biosynthesis of essential compounds such as amino acids. However, grafting experiments suggest that fba3 is dysfunctional in leaf phloem transport, and we suggest that a block in photoassimilate export from leaves causes the buildup of high carbohydrate concentrations and retarded growth. [ABSTRACT FROM AUTHOR]

Summary: Cassava is an important staple crop in sub‐Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in a greenhouse in Erlangen, Germany, and in the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of RuBisCO:phosphoenolpyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely to be attributed to high activities of enzymes in the Calvin–Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This situation was especially so in greenhouse‐grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhanced sink capacity in the high light and low nitrogen environment in the field. Overall, these results indicated that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement. Significance Statement: Cassava is an important staple crop especially in Africa and understanding its metabolic properties, including source–sink relationships and nutrient‐use efficiency, is crucial to improve its productivity. Detailed characterization of more than 100 metabolites and enzyme activities in four tissues of six African cassava cultivars under both greenhouse and field conditions highlighted the close relationships of carbon assimilation rate, K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation with storage root yield. [ABSTRACT FROM AUTHOR]

In shade-intolerant plants, the perception of proximate neighbors rapidly induces architectural changes resulting in elongated stems and reduced leaf size. Sensing and signaling steps triggering this modified growth program have been identified. However, the underlying changes in resource allocation that fuel stem growth remain poorly understood. Through 14CO2 pulse labeling of Brassica rapa seedlings, we show that perception of the neighbor detection signal, low ratio of red to far-red light (R:FR), leads to increased carbon allocation from the major site of photosynthesis (cotyledons) to the elongating hypocotyl. While carbon fixation and metabolite levels remain similar in low R:FR, partitioning to all downstream carbon pools within the hypocotyl is increased. Genetic analyses using Arabidopsis thaliana mutants indicate that low-R:FR-induced hypocotyl elongation requires sucrose transport from the cotyledons and is regulated by a PIF7-dependent metabolic response. Moreover, our data suggest that starch metabolism in the hypocotyl has a growth-regulatory function. The results reveal a key mechanism by which metabolic adjustments can support rapid growth adaptation to a changing environment. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens L.) is one of the most important legumes for fodder production in temperate climates, particularly in intensive pasture systems. Like many other forage legumes, it lacks the energy content to maximize productivity of modern ruminant livestock breeds. White clover produces water-soluble carbohydrates and starch in its leaves as a diurnal product of photosynthesis. However, little is known about the genetically encoded variability of diel changes in carbohydrate content. We assessed the amount of glucose, fructose, sucrose, and starch in the leaves of 185 plants of a genetically diverse white clover population. Water-soluble carbohydrates only provided on average 10.6% of dry weight (DW) of the total analyzed non-structural carbohydrate (NSC) content at the end of the day (ED), while starch supplied 89.4% of the NSC content. The top 5% of individuals accumulated over 25% of their DW as starch at ED. The leaf starch content at ED showed up to a threefold difference between genotypes, with a repeatability value of 0.95. Our experiments illustrate both the physical potential of white clover to serve as a competitive energy source to meet the demand of modern ruminant livestock production and the genetic potential to improve this trait by breeding. [ABSTRACT FROM AUTHOR]

Background: Photosynthetic assimilation of carbon is a defining feature of the plant kingdom. The fixation of large amounts of carbon dioxide supports the synthesis of carbohydrates, which make up the bulk of plant biomass. Exact measurements of carbon assimilation rates are therefore crucial due to their impact on the plants metabolism, growth and reproductive success. Commercially available single-leaf cuvettes allow the detailed analysis of many photosynthetic parameters, including gas exchange, of a selected leaf area. However, these cuvettes can be difficult to use with small herbaceous plants such as Arabidopsis thaliana or plants having delicate or textured leaves. Furthermore, data from single leaves can be difficult to scale-up for a plant shoot with a complex architecture and tissues in different physiological states. Therefore, we constructed a versatile system-EGES-1-to simultaneously measure gas exchange in the whole shoots of multiple individual plants. Our system was designed to be able record data continuously over several days. Results: The EGES-1 system yielded comparable measurements for eight plants for up to 6 days in stable, physiologically realistic conditions. The chambers seals have negligible permeability to carbon dioxide and the system is designed so as to detect any bulk-flow air leaks. We show that the system can be used to monitor plant responses to changing environmental conditions, such as changes in illumination or stress treatments, and to compare plants with phenotypically severe mutations. By incorporating interchangeable lids, the system could be used to measure photosynthetic gas exchange in several genera such as Arabidopsis, Nicotiana, Pisum, Lotus and Mesembryanthemum. Conclusion: EGES-1 can be introduced into a variety of growth facilities and measure gas exchange in the shoots diverse plant species grown in different growth media. It is ideal for comparing photosynthetic carbon assimilation of wild-type and mutant plants and/or plants undergoing selected experimental treatments. The system can deliver valuable data for whole-plant growth studies and help understanding mutant phenotypes. Overall, the EGES-1 is complementary to the readily-available single leaf systems that focus more on the photosynthetic process in within the leaf lamina. [ABSTRACT FROM AUTHOR]

Plant growth involves the coordinated distribution of carbon resources both towards structural components and towards storage compounds that assure a steady carbon supply over the complete diurnal cycle. We used 14 CO2 labelling to track assimilated carbon in both source and sink tissues. Source tissues exhibit large variations in carbon allocation throughout the light period. The most prominent change was detected in partitioning towards starch, being low in the morning and more than double later in the day. Export into sink tissues showed reciprocal changes. Fewer and smaller changes in carbon allocation occurred in sink tissues where, in most respects, carbon was partitioned similarly, whether the sink leaf assimilated it through photosynthesis or imported it from source leaves. Mutants deficient in the production or remobilization of leaf starch exhibited major alterations in carbon allocation. Low-starch mutants that suffer from carbon starvation at night allocated much more carbon into neutral sugars and had higher rates of export than the wild type, partly because of the reduced allocation into starch, but also because of reduced allocation into structural components. Moreover, mutants deficient in the plant's circadian system showed considerable changes in their carbon partitioning pattern suggesting control by the circadian clock. [ABSTRACT FROM AUTHOR]

In illuminated chloroplasts, one mechanism involved in reduction-oxidation (redox) homeostasis is the malate-oxaloacetate (OAA) shuttle. Excess electrons from photosynthetic electron transport in the form of nicotinamide adenine dinucleotide phosphate, reduced are used by NADP-dependent malate dehydrogenase (MDH) to reduce OAA to malate, thus regenerating the electron acceptor NADP. NADP-MDH is a strictly redox-regulated, light-activated enzyme that is inactive in the dark. In the dark or in nonphotosynthetic tissues, the malate-OAA shuttle was proposed to be mediated by the constitutively active plastidial NAD-specific MDH isoform (pdNAD-MDH), but evidence is scarce. Here, we reveal the critical role of pdNAD-MDH in Arabidopsis (Arabidopsis thaliana) plants. A pdnad-mdh null mutation is embryo lethal. Plants with reduced pdNAD-MDH levels by means of artificial microRNA (miR-mdh-1) are viable, but dark metabolism is altered as reflected by increased nighttime malate, starch, and glutathione levels and a reduced respiration rate. In addition, miR-mdh-1 plants exhibit strong pleiotropic effects, including dwarfism, reductions in chlorophyll levels, photosynthetic rate, and daytime carbohydrate levels, and disordered chloroplast ultrastructure, particularly in developing leaves, compared with the wild type. pdNAD-MDH deficiency in miR-mdh-1 can be functionally complemented by expression of a microRNA-insensitive pdNAD-MDH but not NADP-MDH, confirming distinct roles for NAD- and NADP-linked redox homeostasis. [ABSTRACT FROM AUTHOR]

Arabidopsis proton gradient regulation ( pgr) mutants have high chlorophyll fluorescence and reduced non-photochemical quenching ( NPQ) caused by defects in photosynthetic electron transport. Here, we identify PGR6 as the chloroplast lipid droplet (plastoglobule, PG) kinase ABC1 K1 (activity of bc1 complex kinase 1). The members of the ABC1/ ADCK/ Ubi B family of atypical kinases regulate ubiquinone synthesis in bacteria and mitochondria, and impact various metabolic pathways in plant chloroplasts. Here, we demonstrate that abc1k1 has a unique photosynthetic and metabolic phenotype that is distinct from that of the abc1k3 homolog. The abc1k1/pgr6 single mutant is specifically deficient in the electron carrier plastoquinone, as well as in β-carotene and the xanthophyll lutein, and is defective in membrane antioxidant tocopherol metabolism. After 2 days of continuous high light stress, abc1k1/pgr6 plants suffer extensive photosynthetic and metabolic perturbations, strongly affecting carbohydrate metabolism. Remarkably, however, the mutant acclimates to high light after 7 days together with a recovery of carotenoid levels and a drastic alteration in the starch-to-sucrose ratio. Moreover, ABC1 K1 behaves as an active kinase and phosphorylates VTE1, a key enzyme of tocopherol (vitamin E) metabolism in vitro. Our results indicate that the ABC1 K1 kinase constitutes a new type of regulatory link between photosynthetic activity and chloroplast metabolism. [ABSTRACT FROM AUTHOR]

Background Plant biomass consists primarily of carbohydrates derived from photosynthesis. Monitoring the assimilation of carbon via the Calvin-Benson cycle and its subsequent utilisation is fundamental to understanding plant growth. The use of stable and radioactive carbon isotopes, supplied to plants as CO2, allows the measurement of fluxes through the intermediates of primary photosynthetic metabolism, long-distance transport of sugars in the vasculature, and the synthesis of structural and storage components. Results Here we describe the design of a system for supplying isotopically labelled CO2 to single leaves of Arabidopsis thaliana. We demonstrate that the system works well using short pulses of 14CO2 and that it can be used to produce robust qualitative and quantitative data about carbon export from source leaves to the sink tissues, such as the developing leaves and the roots. Time course experiments show the dynamics of carbon partitioning between storage as starch, local production of biomass, and export of carbon to sink tissues. Conclusion This isotope labelling method is relatively simple to establish and inexpensive to perform. Our use of 14CO2 helps establish the temporal and spatial allocation of assimilated carbon during plant growth, delivering data complementary to those obtained in recent studies using 13CO2 and MS-based metabolomics techniques. However, we emphasise that this labelling device could also be used effectively in combination with 13CO2 and MS-based techniques. [ABSTRACT FROM AUTHOR]

Summary Many plants, including Arabidopsis thaliana, retain a substantial portion of their photosynthate in leaves in the form of starch, which is remobilized to support metabolism and growth at night. ADP-glucose pyrophosphorylase (AGPase) catalyses the first committed step in the pathway of starch synthesis, the production of ADP-glucose. The enzyme is redox-activated in the light and in response to sucrose accumulation, via reversible breakage of an intermolecular cysteine bridge between the two small (APS1) subunits. The biological function of this regulatory mechanism was investigated by complementing an aps1 null mutant ( adg1) with a series of constructs containing a full-length APS1 gene encoding either the wild-type APS1 protein or mutated forms in which one of the five cysteine residues was replaced by serine. Substitution of Cys81 by serine prevented APS1 dimerization, whereas mutation of the other cysteines had no effect. Thus, Cys81 is both necessary and sufficient for dimerization of APS1. Compared to control plants, the adg1/ APS1C81S lines had higher levels of ADP-glucose and maltose, and either increased rates of starch synthesis or a starch-excess phenotype, depending on the daylength. APS1 protein levels were five- to tenfold lower in adg1/ APS1C81S lines than in control plants. These results show that redox modulation of AGPase contributes to the diurnal regulation of starch turnover, with inappropriate regulation of the enzyme having an unexpected impact on starch breakdown, and that Cys81 may play an important role in the regulation of AGPase turnover. [ABSTRACT FROM AUTHOR]

A putative phosphatase, LSF1 (for LIKE SEX4; previously PTPKIS2), is closely related in sequence and structure to STARCH- EXCESS4 (SEX4), an enzyme necessary for the removal of phosphate groups from starch polymers during starch degradation in Arabidopsis (Arabidopsis thaliana) leaves at night. We show that LSF1 is also required for starch degradation: lsf1 mutants, like sex4 mutants, have substantially more starch in their leaves than wild-type plants throughout the diurnal cycle. LSF1 is chloroplastic and is located on the surface of starch granules. Isf1 and sex4 mutants show similar, extensive changes relative to wild-type plants in the expression of sugar-sensitive genes. However, although LSF1 and SEX4 are probably both involved in the early stages of starch degradation, we show that LSF1 neither catalyzes the same reaction as SEX4 nor mediates a sequential step in the pathway. Evidence includes the contents and metabolism of phosphorylated glucans in the single mutants. The sex4 mutant accumulates soluble phospho-oligosaccharides undetectable in wild-type plants and is deficient in a starch granule-dephosphorylating activity present in wild-type plants. The isfi mutant displays neither of these phenotypes. The phenotype of the lsf1/sex4 double mutant also differs from that of both single mutants in several respects. We discuss the possible role of the LSF1 protein in starch degradation. [ABSTRACT FROM AUTHOR]

In most plants, a large fraction of photo-assimilated carbon is stored in the chloroplasts during the day as starch and remobilized during the subsequent night to support metabolism. Mutations blocking either starch synthesis or starch breakdown in Arabidopsis thaliana reduce plant growth. Maltose is the major product of starch breakdown exported from the chloroplast at night. The maltose excess 1 mutant (mex1), which lacks the chloroplast envelope maltose transporter, accumulates high levels of maltose and starch in chloroplasts and develops a distinctive but previously unexplained chlorotic phenotype as leaves mature. The introduction of additional mutations that prevent starch synthesis, or that block maltose production from starch, also prevent chlorosis of mex1. In contrast, introduction of mutations in disproportionating enzyme (DPE1) results in the accumulation of maltotriose in addition to maltose, and greatly increases chlorosis. These data suggest a link between maltose accumulation and chloroplast homeostasis. Microscopic analyses show that the mesophyll cells in chlorotic mex1 leaves have fewer than half the number of chloroplasts than wild-type cells. Transmission electron microscopy reveals autophagy-like chloroplast degradation in both mex1 and the dpe1/mex1 double mutant. Microarray analyses reveal substantial reprogramming of metabolic and cellular processes, suggesting that organellar protein turnover is increased in mex1, though leaf senescence and senescence-related chlorophyll catabolism are not induced. We propose that the accumulation of maltose and malto-oligosaccharides causes chloroplast dysfunction, which may by signaled via a form of retrograde signaling and trigger chloroplast degradation. [ABSTRACT FROM PUBLISHER]

ABSTRACTThe aim of this work was to investigate the effects on carbohydrate metabolism of a reduction in the capacity to degrade leaf starch in Arabidopsis. The major roles of leaf starch are to provide carbon for sucrose synthesis, respiration and, in developing leaves, for biosynthesis and growth. Wild-type plants were compared with plants of a starch-excess mutant line (sex4) deficient in a chloroplastic isoform of endoamylase. This mutant has a reduced capacity for starch degradation, leading to an imbalance between starch synthesis and degradation and the gradual accretion of starch as the leaves age. During the night the conversion of starch into sucrose in the mutant is impaired; the leaves of the mutant contained less sucrose than those of the wild type and there was less movement of 14C-label from starch to sucrose in radio-labelling experiments. Furthermore, the rate of assimilate export to the roots during the night was reduced in the mutant compared with the wild type. During the day however, photosynthetic partitioning was altered in the mutant, with less photosynthate partitioned into starch and more into sugars. Although the sucrose content of the leaves of the mutant was similar to the wild type during the day, the rate of export of sucrose to the roots was increased more than two-fold. The changes in carbohydrate metabolism in the mutant leaves during the day compensate partly for its reduced capacity to synthesize sucrose from starch during the night. [ABSTRACT FROM AUTHOR]

Starch and sucrose are the primary products of photosynthesis in the leaves of most plants. Starch represents the major plant storage carbohydrate providing energy during the times of heterotrophic growth. Starch metabolism has been studied extensively, leading to a good knowledge of the numerous enzymes involved. In contrast, understanding of the regulation of starch metabolism is fragmentary. This review summarises briefly the known steps in starch metabolism, highlighting recent discoveries. We also focus on evidence for potential regulatory mechanisms of the enzymes involved. These mechanisms include allosteric regulation by metabolites, redox regulation, protein–protein interactions and reversible protein phosphorylation. Modern systems biology and bioinformatic approaches are uncovering evidence for extensive post-translational protein modifications that may underlie enzyme regulation and identify novel proteins which may be involved in starch metabolism. [Copyright &y& Elsevier]

Abstract: In chloroplasts, the ferredoxin/thioredoxin pathway regulates enzyme activity in response to light by reduction of regulatory disulfides in target enzymes, ensuring coordination between photosynthesis and diurnal metabolism. Although earlier studies have suggested that many starch metabolic enzymes are similarly regulated, redox regulation has only been verified for a few of these in vitro. Using zymograms and enzyme assays, we performed a comprehensive analysis of the redox sensitivity of known starch metabolising enzymes in extracts of Arabidopsis thaliana. Manipulation of redox potentials revealed that several enzymatic activities where activated by reduction at physiologically relevant potentials. Among these where the isoamylase complex AtISA1/AtISA2, the limit dextrinase AtLDA, starch synthases AtSS1 and AtSS3, and the starch branching enzyme AtBE2. The reversibility of the redox reaction was confirmed by enzyme assays for AtLDA, AtSS1 and AtSS3. Analysis of an AtBAM1 knock-out mutant identified an additional redox sensitive β-amylase activity, which was most likely AtBAM3. A similar requirement for reducing conditions was observed for recombinant chloroplastic α-amylase (AtAMY3) activity. This study adds further candidates to the list of reductively activated starch metabolising enzymes and supports the view that redox regulation plays a role in starch metabolism. [Copyright &y& Elsevier]