Project description:Purpose: Acclimation referes to reversible responses that plants trigger under frequently and moderate changes in natural environments, mostly light intensity and temperature. To better understand acclimation in Arabidopsis thaliana, modulators and integrators for this process should be identified. To achieve this goal, a dynamic set-up was designed to systematically cultivate Arabidopsis plants under moderate high light, heat and cold and a multiple high-throughput strategy was conducted to monitor changes in transcriptome, proteome and metabolome. As part of this comprehensive characterisation, lncRNA-Seq has been carried out to investigate transcriptome changes and further integrated in conditional correlation networks. Methods: lncRNA-Seq libraries were prepared from 14-d-old plants cultivated under standard control conditions or acclimated to high light, cold or heat for 4 d and then de-acclimated under normal conditions for 4 additional days. Standard Illumina protocols were used for lncRNA-Seq sequencing. Unless some quality issue in libraries was detected, triplicates for 3 independent plants were used. Adaptor sequences were removed with Trimmomatic and resulting reads mapped to the Arabidopsis genome (Araport11) with Tophat 2.1.1. FPKM reads were quantified with Cufflinks to provide processed data files and differential expression analysis were conducted with featureCounts/DEseq2 pipeline. Results: lncRNA-Seq libraries contained 10 milion reads each. Transcript analysis for differential gene expression was conducted according to the Tophat/featureCounts/DESeq2 pipeline. To declare significant differences, a cut-off for absolute log2(FC) ≥ 1 compared to the corresponding control and FDR ≤ 0.05 was applied. Transcripts significantly different in at least one time-point were considered for subsequent analysis. Accordingly, high light treatments caused changes in 2683 transcripts, followed by 3470 under heat and 6882 under cold. Further data analysis revealed that more than 12% of all altered transcripts were commonly miss-regulated among the three treatments. From a dynamic point of view, transcriptional changes occurred from 3h to 4d of treatment in all treatments and tend to recover to the initial state after 2 and 4d of de-acclimation. Conclusions: the reversibility of the transcriptional changes during the recovery phase validated the conditions of our set-up to investigate acclimation. Moreover, the existance of a common fraction of transcripts that responded to the three conditions unveiled a central response to acclimation.

Project description:During low temperature exposure, temperate plant species increase their freezing tolerance in a process termed cold acclimation. During deacclimation in response to warm temperatures cold acclimated plants lose freezing tolerance and resume growth and development. While considerable effort has been directed toward understanding the molecular and metabolic basis of cold acclimation, much less information is available about the regulation of deacclimation. Here, we report metabolic (GC-MS) and transcriptional (microarrays, qRT-PCR) responses underlying deacclimation during the first 24 h after a shift of cold acclimated Arabidopsis thaliana (Columbia-0) plants to warm temperature. The data revealed a faster response of the transcriptome than of the metabolome and provided evidence for tightly regulated temporal responses at both levels. Metabolically deacclimation is associated with decreasing contents of sugars, amino acids and glycolytic and TCA cycle intermediates, indicating an increased need for carbon sources and respiratory energy production associated with growth resumption under warm temperature conditions. Deacclimation also involves extensive down-regulation of protein synthesis and changes in the metabolism of lipids and cell wall components. Altered hormonal regulation appears particularly important during deacclimation, with changes in the expression of genes related to auxin, gibberellin, brassinosteroid, jasmonate and ethylene metabolisms. Several transcription factor families controlling fundamental aspects of plant development are significantly regulated during deacclimation, emphasizing that loss of freezing tolerance and growth resumption are interrelated processes that are transcriptionally highly interrelated. Expression patterns of some clock oscillator components during deacclimation resembled those under warm conditions, indicating at least partial re-activation of the circadian clock. This study provide the first comprehensive analysis of the regulation of deacclimation in cold acclimated plants. The data indicate cascades of rapidly regulated genes and metabolites that underly the developmental switch resulting in reduced freezing tolerance and the resumption of growth. They constitute a reference dataset of genes, metabolites and pathways that are crucial during the first rapid phase of deacclimation and will be useful for the further analysis of this important but under-researched plant process. We used whole genome microarrays to monitor changes in gene expression in the Arabidopsis thaliana accession Columbia-0 during the first 24 h after a shift of cold acclimated plants to warm temperature.

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 3M-bM-^@M-^YIVT labelling kit (Santa Clara, CA, USA) and hybridized to the Affymetrix wheat genome array (Santa Clara, Ca, USA) at the McGill University and GM-CM-)nome QuM-CM-)bec 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:Purpose: Overexpression of VDE, ZEP and PsbS (VPZ) in plants confers enhanced dynamics of non-photochemical quenching of NPQ under FL light. VPZ overexpression in tobacco has been reported to increase plant biomass under fluctuating light. However, our work demonstrates that such strategy had no advantageous effect when asssayed in Arabidopsis thaliana. To investigate whether this observation is due to impairements in signaling pathways due to the expression of VPZ in Arabidopsis thaliana, transcriptome profiles of VPZ plants exposed to fluctuating light or high light were conducted. Methods: mRNA-Seq libraries were prepared from 21-d-old Col0 plants and VPZ lines #2 and #4 cultivated under standard control conditions and then exposed to fluctuating light or high light for 6h and 30 h. Standard Illumina protocols were used for mRNA-Seq sequencing. Triplicates for 3 independent plants were used. Adaptor sequences were removed with Trimmomatic and resulting reads mapped to the Arabidopsis genome (Araport11) with Tophat 2.1.1. Normalised counts reads were quantified with featureCounts to provide processed data files and differential expression analysis were conducted with the DEseq2 pipeline. Results: mRNA-Seq libraries contained app. 9 milion reads each. Transcript analysis for differential gene expression was conducted according to the Tophat/featureCounts/DESeq2 pipeline. To declare significant differences, a cut-off for absolute log2(FC) ≥ 1 compared to the initial timepoint (0h) and FDR ≤ 0.05 was applied. Significant transcripts exclusively found for Col0 and both VPZ lines in each time-point were considered for subsequent analysis. Accordingly, 528 and 415 transcripts (6h and 30h) were found for Col0, and 326 and 896 (6h and 30h) for the VPZ under control conditions. For FL, 490 and 591 transcripts qualified as specific (6h and 30h) for Col0 and 938 and 401 (6h and 30h) for VPZ. Strikingly, the amount of transcripts raised to 2847 and 2902 DEGs (6h and 30h) for Col0, whereas only 546 and 304 (6h and 30h) were detected for VPZ under HL. transcripts). Conclusions: the overexpression of VPZ in Arabidopsis leads to particular transcriptome response under fluctuating light related to changes in photosynthesis and response to abscisic acid, among all. However, Col0 displayed wider transcriptome responses than VPZ after exposure to high light .

Dataset Information

Comparison of transcript profiles of acclimated and de-acclimated Arabidopsis plants to high light, cold and heat.

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