Physiological, biochemical and genome-wide transcriptional analysis reveals that elevated CO2 mitigates the impact of combined heat wave and drought stress in Arabidopsis thaliana at multiple organizational levels
ABSTRACT: Genome-wide transcriptional profiling of Arabidopsis thaliana to a combination of heatwave and drought under ambient and elevated CO2. Goal of this study was elucidate the transcriptional responses to a combination of heat wave and drought, and to see how these responses are modifed under future climate (high) CO2. Climate changes increasingly threaten plant growth and productivity. Such changes are complex and involve multiple environmental factors, including rising CO2 levels and climate extreme events. As the molecular and physiological mechanisms underlying plant responses to realistic future climate extreme conditions are still poorly understood, a multiple organizational level-analysis (i.e. eco-physiological, biochemical and transcriptional) was performed, using Arabidopsis exposed to incremental heat wave and water deficit under elevated CO2.The climate extreme resulted in biomass reduction, photosynthesis inhibition, and considerable increases in stress parameters. Photosynthesis was a major target as demonstrated at the physiological and transcriptional levels. In contrast, the climate extreme treatment induced a protective effect on oxidative membrane damage, most likely as a result of strongly increased lipophilic antioxidants and membrane-protecting enzymes. Elevated CO2 significantly mitigated the negative impact of a combined heat and drought, as apparent in biomass reduction, photosynthesis inhibition, chlorophyll fluorescence decline, H2O2 production and protein oxidation. Analysis of enzymatic and molecular antioxidants revealed that the stress-mitigating CO2 effect operates through up-regulation of antioxidant defense metabolism, as well as by reduced photorespiration resulting in lowered oxidative pressure. Therefore, exposure to future climate extreme episodes will negatively impact plant growth and production, but elevated CO2 is likely to mitigate this effect. Transcriptome analysis was performed by Agilent Arabidopsis (V4) 4x44K platform which represented all known genes in the Arabidopsisgenome. Experiments were performed using a modified loop design (Knapen et al., 2009). This design consisted of total 8 arrays; sample from each treatment was labelled once and has 4 biological replicates, two of which were labelled in red and two in green
Project description:Simulating predicted future climate conditions, stress response and stress-related memory after one week of recovery were transcriptionally characterised in young and old leaves, phloem-bark, developing xylem and roots of 3-month-old Grey poplar plants that had undergone three weeks of stress or were kept under control conditions. The control conditions include ambient or elevated CO2 levels (380 μL L-1 and 500 μL L-1, respectively) with a daily maximum temperature of 27 °C. The stress conditions include a periodic and a chronic drought-heat scenario at elevated CO2 levels (500 μL L-1) with a daily maximum temperature of 33 °C. The periodic stress treatment included three cycles of reduced irrigation (50%, 60% and 70% reduction compared with the controls), each one lasting for six days; between the cycles, there were recovery periods with a duration of two days and a daily maximum temperature of 27 °C. In the chronic stress treatment, irrigation was gradually reduced for 22 days, down to 70% reduction compared with the controls. Three biological replicates were examined per group defined by a specific environmental condition (droughtPER: periodic stress, droughtCHR: chronic stress, control500: elevated CO2 control, control380: ambient CO2 control), a specific harvesting time (S: stress phase, R: recovery phase) and a specific tissue (LE1: young leaves, LE2: old leaves, PHL: phloem-bark, XYL: developing xylem, ROO: roots). For stress phase ambient CO2 control in old leaves, one replicate failed quality control.
Project description:This study compared the photosynthetic performance and the global gene expression of the winter hardy wheat Triticum aestivum cv Norstar grown under non-acclimated (NA) or cold-acclimated (CA) condition at either ambient CO2 or elevated CO2 (EC). CA Norstar maintained comparable light saturated and CO2 saturated rates of photosynthesis but lower quantum requirements for photosystem II and non photochemical quenching relative to NA plants even at EC. Neither NA nor CA plants were sensitive to feedback inhibition of photosynthesis at EC. Global gene expression using microarray combined with bioinformatics analysis revealed that genes affected by EC were 3 times higher in NA (1022 genes) compared to CA (372 genes) Norstar. The most striking effect was the down-regulation of genes involved in the plant defense responses in NA Norstar. In contrast, cold acclimation reversed this down regulation due to the cold induction of genes involved in plant pathogenesis resistance, and cellular and chloroplast protection. These results suggest that EC have less impact on plant performance and productivity in cold adapted winter hardy plants in the northern climates compared to warmer environments. Selection for cereal cultivars with constitutively higher expression of biotic stress defense genes may be necessary under EC during the warm growth period and in warmer climates. Twelve replicate pots with 3 plants per pot were grown at either NA or CA conditions at either ambient or EC. To minimize any possible chamber effects, the 12 replicate pots at each growth condition were distributed between two growth chambers. A total of 3 biological replicates for each condition were used for microarray analyses. Each biological replicate sample was obtained by pooling three whole fully expanded 3rd leaves from different plants harvested randomly. The different biological samples of Norstar winter wheat leaves were ground in dry ice to fine powder and total RNA was extracted with trizol (Invitrogen, Burlington, ON, CA). Total RNA was cleaned using RNeasy plant mini kit (Qiagen) and integrity was determined on agarose gel and on a bioanalyser (Agilent 2100). Synthesized cDNAs were transcribed to cRNAs with the 3’IVT labelling kit (Santa Clara, CA, USA) and hybridized to the Affymetrix wheat genome array (Santa Clara, Ca, USA) at the McGill University and Génome Québec Innovation Centre (Montreal, Qc, CA). The experimental design consisted of three biological replicates for each of the four growth conditions, 1: Non-acclimated (NA) at ambient CO2 (AC) (NAAC); 2: Cold-acclimated (CA) at ambient CO2 (AC) (CAAC); 3: Non-acclimated (NA) at elevated CO2 (EC) (NAEC); 4: Cold-acclimated (CA) at elevated CO2 (EC) (CAEC). Thus, a total of 3 biological samples from each of the 4 growth conditions described above were used for hybridizations.
Project description:Transcriptomic profiling of the diatom Thalassiosira pseudonana at normal and elevlated CO2 levels and at normal and elevated light levels. Common reference total RNA (Agilent Quick-Amp Cy3-labeled) was used in all arrays as an internal standard. Triplicate batch cultures grown at normal (~400ppm) and elevated (~800ppm) CO2 levels, both at i) normal or ii) elevated light levels. Samples were taken during a) exponential and b) stationary growth during all growth experiments. Result: 48 total transcriptomic measurements: [3 parallel replicates] x [400ppm, 800ppm] x [normal light, high light] x [exponential, stationary] x [2 serial replicates]
Project description:This experiment showed the microarray expression of a barley recessive mutant (G132) and its wild type (Hordeum vulgare cv. Graphic) under high CO2 concentration. The homozygous mutation has a strong pleiotropic nature affecting many aspects of plant. In order to identify target genes of this mutation, changes in gene expression of mutant and its responses to elevated CO2 were compared to wild type.
Project description:Plant respiration responses to elevated growth [CO2] are key uncertainties in predicting future crop and ecosystem function. In particular, the effects of elevated growth [CO2] on respiration over leaf development are poorly understood. This study tested the prediction that, due to greater whole-plant photoassimilate availability and growth, elevated [CO2] induces transcriptional reprogramming and a stimulation of nighttime respiration in leaf primordia, expanding leaves, and mature leaves of Arabidopsis thaliana. In primordia, elevated [CO2] altered transcript abundance, but not for genes encoding respiratory proteins. In expanding leaves, elevated [CO2] induced greater glucose content and transcript abundance for some respiratory genes, but did not alter respiratory CO2 efflux. In mature leaves, elevated [CO2] led to greater glucose, sucrose and starch content, plus greater transcript abundance for many components of the respiratory pathway, and greater respiratory CO2 efflux. Therefore, growth at elevated [CO2] stimulated dark respiration only after leaves transitioned from carbon sinks into carbon sources. This coincided with greater photoassimilate production by mature leaves under elevated [CO2] and peak respiratory transcriptional responses. It remains to be determined if biochemical and transcriptional responses to elevated [CO2] in primordial and expanding leaves are essential prerequisites for subsequent alterations of respiratory metabolism in mature leaves. Arabidopsis plants were grown in either ambient (370 ppm) or elevated (750 ppm) CO2. Leaf number 10 was harvested when it was a primordia, expanding, or mature in each of the CO2 treatments.
Project description:Diatoms are responsible for ~40% of marine primary productivity1, fueling the oceanic carbon cycle and contributing to natural carbon sequestration in the deep ocean2. Diatoms rely on energetically expensive carbon concentrating mechanisms (CCMs) to fix carbon efficiently at modern levels of CO23–5. How diatoms may respond over the short and long-term to rising atmospheric CO2 remains an open question. Here we use nitrate-limited chemostats to show that the model diatom Thalassiosira pseudonana rapidly responds to increasing CO2 by differentially expressing gene clusters that regulate transcription and chromosome folding and subsequently reduces transcription of photosynthesis and respiration gene clusters under steady-state elevated CO2. These results suggest that exposure to elevated CO2 first causes a shift in regulation and then a metabolic rearrangement. Genes in one CO2-responsive cluster included CCM and photorespiration genes that share a putative cyclic-AMP responsive cis-regulatory sequence, implying these genes are co-regulated in response to CO2 with cAMP as an intermediate messenger. We verified cAMP-induced down-regulation of CCM gene δ-CA3 in nutrient-replete diatom cultures by inhibiting the hydrolysis of cAMP. These results indicate an important role for cAMP in down-regulating CCM and photorespiration genes under elevated CO2 and provide insights into mechanisms of diatom acclimation in response to climate change. In steady-state experiments: axenic T. pseudonana cells in four biological replicates (duplicate chemostats x 2 experimental runs) were acclimated to nitrate-limitation at 70% (1.5 day-1) of max growth rate for >10 days (>15 generations) under continuous light of 80 µmol photons·m−2·s−1. Cell biomass was maintained at ~2 x 105 cells·mL−1 by 10 μM nitrate and carbonate chemistry stabilized to 300, 475 or 800 μatm CO2, verified by pH and DIC measurements. Transition samples and carbonate chemistry were collected daily from chemostat cultures as CO2 levels were increased from ~300-800 μatm at a rate ≤ 0.2 μatm·min−1 over four consecutive days (6 generations) after pre-acclimation to 300 μatm CO2 and nitrate-limitation.
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. Transciptomic expression profiles indicated that genes involved in carbon/nitrogen metabolism, and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency. Bradyrhizobium japonicum strains were grown in the soybean rhizosphere under two different CO2 concentrations. Transcriptional profiling of B. japonicum was compared between cells grown under elevated CO2 and ambient conditions. Four biological replicates of each treatment were prepared, and four microarray slides were used for each strain.
Project description:• Reference to published study making use of this data: • Cseke LJ, Tsai C-J, Rogers A, Nelsen MP, White HL, Karnosky DF, Podila GK. (2009) Transcriptomic comparison in the leaves of two aspen genotypes having similar carbon assimilation rates but different allocation patterns under elevated CO2. New Phytologist. submitted. • This study compared the leaf transcription profiles, physiological characteristics, and primary metabolites of two Populus tremuloides genotypes (clones 216 and 271) known to differ in their responses to long-term elevated [CO2] (e[CO2]) at the Aspen FACE site near Rhinelander, WI. • Physiological responses of these clones are similar in photosynthesis, stomatal conductance, and leaf area index under e[CO2] yet very different in growth enhancement (0-10% in clone 216; 40-50% in clone 271). While few genes responded to long-term exposure to e[CO2], the transcriptional activity of leaf e[CO2]-responsive genes was distinctly different between the clones, differentially impacting multiple pathways during both early and late growing seasons. • Analysis of transcript abundance and carbon/nitrogen biochemistry suggests that the CO2-responsive clone (271) partitions C into pathways associated with active defense/response to stress, carbohydrate/starch biosynthesis and subsequent growth. The CO2-unresponsive clone (216) partitions C into pathways associated with passive defense (e.g. lignin, phenylpropanoid) and cell wall thickening. • This study indicates that there is significant variation in expression patterns between different tree genotypes in response to long-term exposure to e[CO2]. Consequently, future efforts to improve productivity or other advantageous traits for carbon sequestration should include an examination of genetic variability in CO2 responsiveness. Keywords: Tree genotype comparison under elevated [CO2] 24 two-channel arrays, directly comparing RNA from trees grown in the ambient (control) [CO2] to RNA derived from the same genotype grown under e[CO2]. For each of 4 experimental conditions (clone 216 early season; clone 271 early season; clone 216 late season; clone 271 late season), three independent biological replicates derived from trees grown in three independent replicate FACE rings were used. In addition, each clone and time point included dye swap reciprocal two-color experiments for each biological replicate. Thus, six data points per cDNA are included (three biological replicates with two technical replicates each).
Project description:This work aims to study the effect of the elevated CO2 concentration on the tomato plant response to the toxicity provoked by ammonium nutrition. Tomato plants (Solanum lycopersicum L. cv. Agora Hybrid F1, Vilmorin®) were grown for 4 week with 15 mM of nitrogen, supplied as nitrate or ammonium, at ambient or elevated CO2 conditions (400 ppm or 800 ppm). Transcription profiling by array was carried out in roots for the four growth conditions assayed and gene expression comparisons were done between N sources and CO2 conditions: i) genes differentially expressed in response to the atmospheric CO2 concentration (800 ppm vs 400 ppm CO2) under nitrate or ammonium nutrition; ii) genes differentially expressed in response to the N source (ammonium vs nitrate) under ambient or elevated condition. 3 biological replicates for each growth condition were analysed.CO2).
Project description:This study contributes large-scale genes expression data of molecular function for a plant system under combined of two CO2 concentration and three Mg levels. It provides an additional example of the power of integrated analyses for the comprehensive study of the molecular physiology of complex biological systems. Moreover, taking into consideration the particular interest of the two investigated perturbations in plant biotechnology, enhanced understanding of the molecular physiology of the plants under climate change conditions could lead to the design of novel metabolic engineering strategies to copy with crops to magnesium problems. Examination of two CO2 concentration and three Mg levels of shoot and root Arabidopsis