Metabolic acclimation-a key to enhancing photosynthesis in changing environments?

Time-resolved systems analysis of the induction of high photosynthetic capacity in Arabidopsis during acclimation to high light

Induction of high photosynthetic capacity is a key acclimation response to high light (HL) for many herbaceous dicot plants; however, the signaling pathways that control this response remain largely unknown. Here, a systems biology approach was utilized to characterize the induction of high photosynthetic capacity in strongly and weakly acclimating Arabidopsis thaliana accessions. Plants were grown for 5 wk in a low light (LL) regime, and time-resolved photosynthetic physiological, metabolomic, and transcriptomic responses were measured during subsequent exposure to HL. The induction of high nitrogen (N) assimilation rates early in the HL shift was strongly predictive of the induction of photosynthetic capacity later in the HL shift. Accelerated N assimilation rates depended on the mobilization of existing organic acid (OA) reserves and increased de novo OA synthesis during the induction of high photosynthetic capacity. Enhanced sucrose biosynthesis capacity increased in tandem with the induction of high photosynthetic capacity, and increased starch biosynthetic capacity was balanced by increased starch catabolism. This systems analysis supports a model in which the efficient induction of N assimilation early in the HL shift begins the cascade of events necessary for the induction of high photosynthetic capacity acclimation in HL.

Natural variation of temperature acclimation of Arabidopsis thaliana

Acclimation is a multigenic trait by which plants adjust photosynthesis and metabolism to cope with a changing environment. Here, natural variations of photosynthetic efficiency and acclimation of the central carbohydrate metabolism were analyzed in response to low and elevated temperatures. For this, 18 natural accessions of Arabidopsis thaliana, originating from Cape Verde Islands and Europe, were grown at 22°C before being exposed to 4°C and 34°C for cold and heat acclimation, respectively. Absolute amounts of carbohydrates were quantified together with their subcellular distribution across plastids, cytosol and vacuole. Linear electron transport rates (ETRs) were determined together with the maximum quantum efficiency of photosystem II (Fv/Fm) for all growth conditions and under temperature fluctuation. Under elevated temperature, ETR residuals under increasing photosynthetic photon flux densities significantly correlated with the degree of temperature fluctuation at the original habitat of accessions, indicating a geographical east/west gradient of photosynthetic acclimation capacities. Plastidial sucrose concentrations positively correlated with maximal ETRs under fluctuating temperature, indicating a stabilizing role within the chloroplast. Our findings revealed specific subcellular carbohydrate distributions that contribute differentially to the photosynthetic efficiency of natural Arabidopsis thaliana accessions across a longitudinal gradient. This sheds light on the relevance of subcellular metabolic regulation for photosynthetic performance in a fluctuating environment and supports the physiological interpretation of naturally occurring genetic variation of temperature tolerance and acclimation.

Metabolome plasticity in 241 Arabidopsis thaliana accessions reveals evolutionary cold adaptation processes

Acclimation and adaptation of metabolism to a changing environment are key processes for plant survival and reproductive success. In the present study, 241 natural accessions of Arabidopsis (Arabidopsis thaliana) were grown under two different temperature regimes, 16 °C and 6 °C, and growth parameters were recorded, together with metabolite profiles, to investigate the natural genome × environment effects on metabolome variation. The plasticity of metabolism, which was captured by metabolic distance measures, varied considerably between accessions. Both relative growth rates and metabolic distances were predictable by the underlying natural genetic variation of accessions. Applying machine learning methods, climatic variables of the original growth habitats were tested for their predictive power of natural metabolic variation among accessions. We found specifically habitat temperature during the first quarter of the year to be the best predictor of the plasticity of primary metabolism, indicating habitat temperature as the causal driver of evolutionary cold adaptation processes. Analyses of epigenome- and genome-wide associations revealed accession-specific differential DNA-methylation levels as potentially linked to the metabolome and identified FUMARASE2 as strongly associated with cold adaptation in Arabidopsis accessions. These findings were supported by calculations of the biochemical Jacobian matrix based on variance and covariance of metabolomics data, which revealed that growth under low temperatures most substantially affects the accession-specific plasticity of fumarate and sugar metabolism. Our findings indicate that the plasticity of metabolic regulation is predictable from the genome and epigenome and driven evolutionarily by Arabidopsis growth habitats.

Salt priming induces low-temperature tolerance in sugar beet via xanthine metabolism

To understand the physiological mechanisms involved in xanthine metabolism during salt priming for improving low-temperature tolerance, salt priming (SP), xanthine dehydrogenase inhibitor (XOI), exogenous allantoin (EA), and back-supplemented EA (XOI + EA) treatments were given and the low-temperature tolerance of sugar beet was tested. Under low-temperature stress, salt priming promoted the growth of sugar beet leaves and increased the maximum quantum efficiency of PS II (Fv/Fm). However, during salt priming, either XOI or EA treatment alone increased the content of reactive oxygen species (ROS), such as superoxide anion and hydrogen peroxide, in the leaves under low-temperature stress. XOI treatment increased allantoinase activity with its gene (BvallB) expression under low-temperature stress. Compared to the XOI treatment, the EA treatment alone and the XOI + EA treatment increased the activities of antioxidant enzymes. At low temperatures, the sucrose content and the activity of key carbohydrate enzymes (AGPase, Cylnv, and FK) were significantly reduced by XOI compared to the changes under salt priming. XOI also stimulated the expression of protein phosphatase 2C and sucrose non-fermenting1-related protein kinase (BvSNRK2). The results of a correlation network analysis showed that BvallB was positively correlated with malondialdehyde, D-Fructose-6-phosphate, and D-Glucose-6-phosphate, and negatively correlated with BvPOX42, BvSNRK2, dehydroascorbate reductase, and catalase. These results suggested that salt-induced xanthine metabolism modulated ROS metabolism, photosynthetic carbon assimilation, and carbohydrate metabolism, thus enhancing low-temperature tolerance in sugar beet. Additionally, xanthine and allantoin were found to play key roles in plant stress resistance.

Salt-Induced Modulation of Ion Transport and PSII Photoprotection Determine the Salinity Tolerance of Amphidiploid Brassicas

Brassica species show varying levels of resistance to salt stress. To understand the genetics underlying these differential stress tolerance patterns in Brassicas, we exposed two widely cultivated amphidiploid Brassica species having different genomes, Brassica juncea (AABB, n = 18) and Brassica napus (AACC, n = 19), to elevated levels of NaCl concentration (300 mM, half the salinity of seawater). B. juncea produced more biomass, an increased chlorophyll content, and fewer accumulated sodium (Na+) and chloride (Cl-) ions in its photosynthesizing tissues. Chlorophyll fluorescence assays revealed that the reaction centers of PSII of B. juncea were more photoprotected and hence more active than those of B. napus under NaCl stress, which, in turn, resulted in a better PSII quantum efficiency, better utilization of photochemical energy with significantly reduced energy loss, and higher electron transport rates, even under stressful conditions. The expression of key genes responsible for salt tolerance (NHX1 and AVP1, which are nuclear-encoded) and photosynthesis (psbA, psaA, petB, and rbcL, which are chloroplast-encoded) were monitored for their genetic differences underlying stress tolerance. Under NaCl stress, the expression of NHX1, D1, and Rubisco increased several folds in B. juncea plants compared to B. napus, highlighting differences in genetics between these two Brassicas. The higher photosynthetic potential under stress suggests that B. juncea is a promising candidate for genetic modifications and its cultivation on marginal lands.

Adaptive strategy of plant cells during chilling: Aspect of ultrastructural reorganization

The review is focused on a comparative analysis of the literature data on the ultrastructural reorganization of leaf cells of higher plants, which differ in their response to low sub-damaging temperatures. The importance of adaptive structural reorganization of cells as a special feature contributing to the surviving strategy of plants existing under changed conditions is emphasized. The adaptive strategy of cold-tolerant plants combines the structural, functional, metabolic, physiological and biochemical reorganization of cells and tissues. These changes constitute a unified program directed to protecting against dehydration and oxidative stress, as well as maintaining basic physiological processes, and above all, photosynthesis. The ultrastructural markers of cold-tolerant plants adaptation to low sub-damaging temperatures include some particular changes in cell morphology. Namely: the following: an increase in the volume of the cytoplasm; the formation of new membrane elements in it; an increase in the size and number of chloroplasts and mitochondria; concentration of mitochondria and peroxisomes near chloroplasts; polymorphism of mitochondria; an increase in the number of cristae in them; the appearance of outgrowths and invaginations in chloroplasts; lumen expansion in the thylakoids; the formation in chloroplasts "sun type" membrane system with reduction in the number and size of grana and domination of non-appressed thylakoids membranes. Due to this adaptive structural reorganization cold-tolerant plants are able to function actively during chilling. On the contrary, structural reorganization of leaf cells of cold-sensitive plants under chilling is aimed at maintaining the basic functions at a minimum level. Cold-sensitive plants "wait out" low temperature stress, and with prolonged exposure to cold, they die from dehydration and intensification of oxidative stress.

Protease inhibitor ASP enhances freezing tolerance by inhibiting protein degradation in kumquat

Cold acclimation is a complex biological process leading to the development of freezing tolerance in plants. In this study, we demonstrated that cold-induced expression of protease inhibitor FmASP in a Citrus-relative species kumquat [Fortunella margarita (Lour.) Swingle] contributes to its freezing tolerance by minimizing protein degradation. Firstly, we found that only cold-acclimated kumquat plants, despite extensive leaf cellular damage during freezing, were able to resume their normal growth upon stress relief. To dissect the impact of cold acclimation on this anti-freezing performance, we conducted protein abundance assays and quantitative proteomic analysis of kumquat leaves subjected to cold acclimation (4°C), freezing treatment (-10°C) and post-freezing recovery (25°C). FmASP (Against Serine Protease) and several non-specific proteases were identified as differentially expressed proteins induced by cold acclimation and associated with stable protein abundance throughout the course of low-temperature treatment. FmASP was further characterized as a robust inhibitor of multiple proteases. In addition, heterogeneous expression of FmASP in Arabidopsis confirmed its positive role in freezing tolerance. Finally, we proposed a working model of FmASP and illustrated how this extracellular-localized protease inhibitor protects proteins from degradation, thereby maintaining essential cellular function for post-freezing recovery. These findings revealed the important role of protease inhibition in freezing response and provide insights on how this role may help develop new strategies to enhance plant freezing tolerance.

Photosynthetic acclimation to changing environments

Plants are exposed to environments that fluctuate of timescales varying from seconds to months. Leaves that develop in one set of conditions optimise their metabolism to the conditions experienced, in a process called developmental acclimation. However, when plants experience a sustained change in conditions, existing leaves will also acclimate dynamically to the new conditions. Typically this process takes several days. In this review, we discuss this dynamic acclimation process, focussing on the responses of the photosynthetic apparatus to light and temperature. We briefly discuss the principal changes occurring in the chloroplast, before examining what is known, and not known, about the sensing and signalling processes that underlie acclimation, identifying likely regulators of acclimation.

Cytosolic fumarase acts as a metabolic fail-safe for both high and low temperature acclimation of Arabidopsis thaliana

Plants acclimate their photosynthetic capacity (Pmax) in response to changing environmental conditions. In Arabidopsis thaliana, photosynthetic acclimation to cold requires the accumulation of the organic acid fumarate, catalysed by a cytosolically localized fumarase, FUM2. However, the role of this accumulation is currently unknown. Here, we use an integrated experimental and modelling approach to examine the role of FUM2 and fumarate across the physiological temperature range. We have studied three genotypes: Col-0; a fum2 mutant in a Col-0 background; and C24, an accession with reduced FUM2 expression. While low temperature causes an increase in Pmax in the Col-0 plants, this parameter decreases following exposure of plants to 30 °C for 7 d. Plants in which fumarate accumulation is partially (C24) or completely (fum2) abolished show a reduced acclimation of Pmax across the physiological temperature range (i.e. Pmax changes less in response to changing temperature). To understand the role of fumarate accumulation, we have adapted a reliability engineering technique, Failure Mode and Effect Analysis (FMEA), to formalize a rigorous approach for ranking metabolites according to the potential risk that they pose to the metabolic system. FMEA identifies fumarate as a low-risk metabolite, while its precursor, malate, is shown to be high risk and liable to cause system instability. We propose that the role of FUM2 is to provide a fail-safe in order to control malate concentration, maintaining system stability in a changing environment. We suggest that FMEA is a technique that is not only useful in understanding plant metabolism but can also be used to study reliability in other systems and synthetic pathways.

Temperature-induced dynamics of plant carbohydrate metabolism

Carbohydrates are direct products of photosynthetic CO₂ assimilation. Within a changing temperature regime, both photosynthesis and carbohydrate metabolism need tight regulation to prevent irreversible damage of plant tissue and to sustain energy metabolism, growth and development. Due to climate change, plants are and will be exposed to both long-term and short-term temperature changes with increasing amplitude. Particularly sudden fluctuations, which might comprise a large temperature amplitude from low to high temperature, pose a challenge for plants from the cellular to the ecosystem level. A detailed understanding of fundamental regulatory processes, which link photosynthesis and carbohydrate metabolism under such fluctuating environmental conditions, is essential for an estimate of climate change consequences. Further, understanding these processes is important for biotechnological application, breeding and engineering. Environmental light and temperature regimes are sensed by a molecular network that comprises photoreceptors and molecular components of the circadian clock. Photosynthetic efficiency and plant productivity then critically depend on enzymatic regulation and regulatory circuits connecting plant cells with their environment and re-stabilising photosynthetic efficiency and carbohydrate metabolism after temperature-induced deflection. This review summarises and integrates current knowledge about re-stabilisation of photosynthesis and carbohydrate metabolism after perturbation by changing temperature (heat and cold).

Superoxide is promoted by sucrose and affects amplitude of circadian rhythms in the evening

Plants must coordinate photosynthetic metabolism with the daily environment and adapt rhythmic physiology and development to match carbon availability. Circadian clocks drive biological rhythms which adjust to environmental cues. Products of photosynthetic metabolism, including sugars and reactive oxygen species (ROS), are closely associated with the plant circadian clock, and sugars have been shown to provide metabolic feedback to the circadian oscillator. Here, we report a comprehensive sugar-regulated transcriptome of Arabidopsis and identify genes associated with redox and ROS processes as a prominent feature of the transcriptional response. We show that sucrose increases levels of superoxide (O₂ ^-), which is required for transcriptional and growth responses to sugar. We identify circadian rhythms of O₂ ^--regulated transcripts which are phased around dusk and find that O₂ ^- is required for sucrose to promote expression of TIMING OF CAB1 (TOC1) in the evening. Our data reveal a role for O₂ ^- as a metabolic signal affecting transcriptional control of the circadian oscillator in Arabidopsis.

Modeling indicates degradation of mRNA and protein as a potential regulation mechanisms during cold acclimation

Plants are constantly exposed to temperature fluctuations, which have direct effects on all cellular reactions because temperature influences reaction likelihood and speed. Chloroplasts are crucial to temperature acclimation responses of plants, due to their photosynthetic reactions whose products play a central role in plant metabolism. Consequently, chloroplasts serve as sensors of temperature changes and are simultaneously major targets of temperature acclimation. The core subunits of the complexes involved in the light reactions of photosynthesis are encoded in the chloroplast. As a result, it is assumed that temperature acclimation in plants requires regulatory responses in chloroplast gene expression and protein turnover. We conducted western blot experiments to assess changes in the accumulation of two photosynthetic complexes (PSII, and Cytb6f complex) and the ATP synthase in tobacco plants over two days of acclimation to low temperature. Surprisingly, the concentration of proteins within the chloroplast varied negligibly compared to controls. To explain this observation, we used a simplified Ordinary Differential Equation (ODE) model of transcription, translation, mRNA degradation and protein degradation to explain how the protein concentration can be kept constant. This model takes into account temperature effects on these processes. Through simulations of the ODE model, we show that mRNA and protein degradation are possible targets for control during temperature acclimation. Our model provides a basis for future directions in research and the analysis of future results.

A Holistic Approach to Study Photosynthetic Acclimation Responses of Plants to Fluctuating Light

Plants in natural environments receive light through sunflecks, the duration and distribution of these being highly variable across the day. Consequently, plants need to adjust their photosynthetic processes to avoid photoinhibition and maximize yield. Changes in the composition of the photosynthetic apparatus in response to sustained changes in the environment are referred to as photosynthetic acclimation, a process that involves changes in protein content and composition. Considering this definition, acclimation differs from regulation, which involves processes that alter the activity of individual proteins over short-time periods, without changing the abundance of those proteins. The interconnection and overlapping of the short- and long-term photosynthetic responses, which can occur simultaneously or/and sequentially over time, make the study of long-term acclimation to fluctuating light in plants challenging. In this review we identify short-term responses of plants to fluctuating light that could act as sensors and signals for acclimation responses, with the aim of understanding how plants integrate environmental fluctuations over time and tailor their responses accordingly. Mathematical modeling has the potential to integrate physiological processes over different timescales and to help disentangle short-term regulatory responses from long-term acclimation responses. We review existing mathematical modeling techniques for studying photosynthetic responses to fluctuating light and propose new methods for addressing the topic from a holistic point of view.

Acclimatisation of guard cell metabolism to long-term salinity

Stomatal movements are enabled by changes in guard cell turgor facilitated via transient accumulation of inorganic and organic ions imported from the apoplast or biosynthesized within guard cells. Under salinity, excess salt ions accumulate within plant tissues resulting in osmotic and ionic stress. To elucidate whether (a) Na⁺ and Cl^- concentrations increase in guard cells in response to long-term NaCl exposure and how (b) guard cell metabolism acclimates to the anticipated stress, we profiled the ions and primary metabolites of leaves, the apoplast and isolated guard cells at darkness and during light, that is, closed and fully opened stomata. In contrast to leaves, the primary metabolism of guard cell preparations remained predominantly unaffected by increased salt ion concentrations. Orchestrated reductions of stomatal aperture and guard cell osmolyte synthesis were found, but unlike in leaves, no increases of stress responsive metabolites or compatible solutes occurred. Diverging regulation of guard cell metabolism might be a prerequisite to facilitate the constant adjustment of turgor that affects aperture. Moreover, the photoperiod-dependent sucrose accumulation in the apoplast and guard cells changed to a permanently replete condition under NaCl, indicating that stress-related photosynthate accumulation in leaves contributes to the permanent closing response of stomata under stress.

Impaired chloroplast positioning affects photosynthetic capacity and regulation of the central carbohydrate metabolism during cold acclimation

Photosynthesis and carbohydrate metabolism of higher plants need to be tightly regulated to prevent tissue damage during environmental changes. The intracellular position of chloroplasts changes due to a changing light regime. Chloroplast avoidance and accumulation response under high and low light, respectively, are well known phenomena, and deficiency of chloroplast movement has been shown to result in photodamage and reduced biomass accumulation. Yet, effects of chloroplast positioning on underlying metabolic regulation are less well understood. Here, we analysed photosynthesis together with metabolites and enzyme activities of the central carbohydrate metabolism during cold acclimation of the chloroplast unusual positioning 1 (chup1) mutant of Arabidopsis thaliana. We compared cold acclimation under ambient and low light and found that maximum quantum yield of PSII was significantly lower in chup1 than in Col-0 under both conditions. Our findings indicated that net CO₂ assimilation in chup1 is rather limited by biochemistry than by photochemistry. Further, cold-induced dynamics of sucrose phosphate synthase differed significantly between both genotypes. Together with a reduced rate of sucrose cycling derived from kinetic model simulations our study provides evidence for a central role of chloroplast positioning for photosynthetic and metabolic acclimation to low temperature.

Acclimation of Photosynthesis to Changes in the Environment Results in Decreases of Oxidative Stress in Arabidopsis thaliana

The dynamic acclimation of photosynthesis plays an important role in increasing the fitness of a plant under variable light environments. Since acclimation is partially mediated by a glucose-6-phosphate/phosphate translocator 2 (GPT2), this study examined whether plants lacking GPT2, which consequently have defective acclimation to increases in light, are more susceptible to oxidative stress. To understand this mechanism, we used the model plant Arabidopsis thaliana [accession Wassilewskija-4 (Ws-4)] and compared it with mutants lacking GPT2. The plants were then grown at low light (LL) at 100 μmol m^-2 s^-1 for 7 weeks. For the acclimation experiments, a set of plants from LL was transferred to 400 μmol m^-2 s^-1 conditions for 7 days. Biochemical and physiological analyses showed that the gpt2 mutant plants had significantly greater activity for ascorbate peroxidase (APX), guiacol peroxidase (GPOX), and superoxide dismutase (SOD). Furthermore, the mutant plants had significantly lower maximum quantum yields of photosynthesis (Fv/Fm). A microarray analysis also showed that gpt2 plants exhibited a greater induction of stress-related genes relative to wild-type (WT) plants. We then concluded that photosynthetic acclimation to a higher intensity of light protects plants against oxidative stress.

Cold acclimation has a differential effect on leaf vascular bundle structure and carbon export rates in natural Arabidopsis accessions originating from southern and northern Europe

Acclimation to low but non-freezing temperature represents an ecologically important process for Arabidopsis thaliana but also for many other plant species from temperate regions. Cold acclimation comprises and affects numerous molecular and physiological processes and the maintenance of sugar supply of sink tissue by photosynthetically active source tissue is essential for plant survival. Here, changes in vascular bundle (VB) structure at the leaf petiole were analysed together with sucrose exudation rates before and after cold acclimation. Six natural Arabidopsis accessions originating from southern and northern Europe were compared. Photosynthetic efficiency, that is, maximum and effective quantum yield of photosystem II, revealed a significant effect of environmental condition. Only for northern accessions was a highly significant negative correlation observed between leaf sucrose exudation rates, xylem, and petiole cross-sectional areas. Furthermore, only for northern accessions was a significant increase of VB and leaf petiole cross-sectional area observed during cold acclimation. In contrast, variance of cross-sectional areas of cold acclimated southern accessions was strongly reduced compared to control plants, while mean areas remained similar under both conditions. In summary, these findings suggest that natural Arabidopsis accessions from northern Europe significantly adjust sink strength and leaf VB structure to maintain plant growth and photosynthesis under low temperature.

From empirical to theoretical models of light response curves - linking photosynthetic and metabolic acclimation

Light response curves (LRCs) describe how the rate of photosynthesis varies as a function of light. They provide information on the maximum photosynthetic capacity, quantum yield, light compensation point and leaf radiation use efficiency of leaves. Light response curves are widely used to capture photosynthetic phenotypes in response to changing environmental conditions. However, models describing these are predominantly empirical and do not attempt to explain behaviour at a mechanistic level. Here, we use modelling to understand the metabolic changes required for photosynthetic acclimation to changing environmental conditions. Using a simple kinetic model, we predicted LRCs across the physiological temperature range of Arabidopsis thaliana and confirm these using experimental data. We use our validated metabolic model to make novel predictions about the metabolic changes of temperature acclimation. We demonstrate that NADPH utilization are enhanced in warm-acclimated plants, whereas both NADPH and CO₂ utilization is enhanced in cold-acclimated plants. We demonstrate how different metabolic acclimation strategies may lead to the same photosynthetic response across environmental change. We further identify that certain metabolic acclimation strategies, such as NADPH utilization, are only triggered when plants are moved beyond a threshold high or low temperature.

Towards identification of molecular mechanism in which the overexpression of wheat cytosolic and plastid glutamine synthetases in tobacco enhanced drought tolerance

Glutamine synthetases (GS) play an essential role in Nitrogen assimilation. Nonetheless, information respecting the molecular functions of GS in drought tolerance (DT) is limited. Here we show that overexpressing cytosolic GS1 or plastidic GS2 gene in tobacco enhanced DT of both root and leaf tissues of the two transgenic seedlings (named as GS1-TR and GS2-TR). RNA-seq analysis on root tissues showed that 83 aquaporin (AQP) genes were identified. Among them, 37 differential expression genes (DEGs) were found in the GS1-TR roots under normal condition, and all were down-regulated; no any DEGs in the GS2-TR roots were found. Contrastingly, under drought, 28 and 32 DEGs of AQP were up-regulated in GS1-TR and GS2-TR roots, respectively. GC-MS analysis on leaf tissues showed that glutamine (Gln) concentrations were negatively correlated AQP expressions in the all four conditions, which suggests that Gln, as a signal molecule, can negatively regulate many AQP expressions. Prestress accumulation of sucrose and proline (Pro) and chlorophyll, and had higher activities of ROS scavengers also contribute the plant DT in both of the two transgenic plants under drought. In addition, 5-aminolevulinic acid (ALA) was up-accumulated in GS2-TR leaves solely under normal condition, which leads to its net photosynthetic rate higher than that in GS1-TR leaves. Last but not the less, the PYL-PP2C-SnRK2 core ABA-signaling pathway was uniquely activated in GS1-TR independent of drought stress (DS). Therefore, our results suggest a possible model reflecting how overexpression of wheat TaGS1 and TaGS2 regulate plant responses to drought.

Mathematical Modeling of Plant Metabolism in a Changing Temperature Regime

Changes in environmental temperature regimes significantly affect plant growth, development and reproduction. Within a multigenic process termed acclimation, many plant species of the temperate region are able to adjust their metabolism to low and high temperature. Temperature-induced metabolic reprogramming is a nonlinear process affecting numerous enzyme kinetic reactions and pathways. The analysis of metabolic reprogramming during temperature acclimation is essentially supported by mathematical modeling which enables the study of nonlinear enzyme kinetics in context of metabolic networks and pathway regulation. This chapter introduces mathematical modeling of plant metabolism during a dynamic environmental temperature regime. A focus is laid on kinetic modeling and thermodynamic constraints.

Dynamics of Plant Metabolism during Cold Acclimation

Plants have evolved strategies to tightly regulate metabolism during acclimation to a changing environment. Low temperature significantly constrains distribution, growth and yield of many temperate plant species. Exposing plants to low but non-freezing temperature induces a multigenic processes termed cold acclimation, which eventually results in an increased freezing tolerance. Cold acclimation comprises reprogramming of the transcriptome, proteome and metabolome and affects communication and signaling between subcellular organelles. Carbohydrates play a central role in this metabolic reprogramming. This review summarizes current knowledge about the role of carbohydrate metabolism in plant cold acclimation with a focus on subcellular metabolic reprogramming, its thermodynamic constraints under low temperature and mathematical modelling of metabolism.