Project description:To investigate the response of Arabidopsis thaliana plants to non-freezing, cool temperatures, we subjected four week old plants to various chilling temperatures at defined times during the diurnal cycle to control for diurnal effects on transcription. From the same plants, metabolites and enzyme activities were measured as well. Interestingly a gradual change could be observed over a wide range of temperatures. Some of which could be attributed to the CBF program. Keywords: time course, different temperatures
Project description:Keeping imbibed seeds at low temperatures for a certain period, so called seed vernalization (SV) treatment, promotes seed germination and subsequent flowering in various plants. Vernalization-promoting flowering requires GSH. However, the expression patterns analyzed by GeneChip arrays showed that increased GSH biosynthesis partially mimics SV treatment in Arabidopsis thaliana. SV treatment (keeping imbibed seeds at 4°C for 24 h) induced a specific pattern of gene expression and promoted subsequent flowering in wild-type plants. A similar pattern was observed at 22°C in transgenic plants (35S-GSH1 plants) overexpressing the γ-glutamylcysteine synthetase gene GSH1, coding an enzyme limiting GSH biosynthesis, under the control of the cauliflower mosaic virus 35S promoter. This pattern was strengthened at 4°C but flowering was less responsive to SV treatment. There was a difference in the transcript behaviour of the flowering repressor FLC between wild-type and 35S-GSH1 plants. Unlike other genes responsive to SV treatment, SV-dependent decrease in FLC in wild-type plants was reversed in 35S-GSH1 plants. SV treatment increased GSSG level in wild-type seeds, whereas GSSG level was high in 35S-GSH1 plants, even at a non-vernalizing temperature. Taking into consideration that low temperatures stimulate GSH biosynthesis and bring about oxidative stress, GSSG is considered to trigger low temperature response, but enhanced GSH synthesis was not enough for mimicking SV treatment. To complete it, it essentially required the cellular redox retransition from the oxidized to the reduced state that is observed after the seed vernalization treatment.
Project description:Plants can respond to low temperatures with diverse mechanisms occurred at transcriptional and translational levels. N6-methyladenosine (m6A) is the most prevalent mRNA modification in eukaryotes that acts as a new emerging layer of epitranscriptomic gene regulation. However, the cellular roles of m6A in plant response to low temperatures remain largely unknown. Here we show that mRNA m6A modification is indispensable for Arabidopsis growth under chilling conditions.
Project description:How plants control the transition to flowering in response to ambient temperature is only beginning to be understood. In Arabidopsis thaliana, the MADS-box transcription factor genes FLOWERING LOCUS M (FLM) and SHORT VEGETATIVE PHASE (SVP) have key roles in this process. FLM is subject to temperature-dependent alternative splicing, producing two splice variants, FLM-β and FLM-δ, which compete for interaction with the floral repressor SVP. The SVP/FLM-β complex is predominately formed at low temperatures and prevents precocious flowering. In contrast, the competing SVP FLM-δ complex is impaired in DNA binding and acts as a dominant negative activator of flowering at higher temperatures. Our results demonstrate the importance of temperature-dependent alternative splicing in modulating the timing of the floral transition in response to environmental change.
Project description:Plants in temperate regions have evolved mechanisms to survive sudden temperature drops. Previous reports have indicated that the cold acclimation mechanism is light-dependent and does not fully operate under a low light intensity. In these studies, plants were grown under a long-day photoperiod and were more sensitive to freezing stress. However, winter annuals like Arabidopsis thaliana Col-0 germinate in the fall, overwinter as rosettes, and therefore must acclimate under short photoperiods and low irradiance. The role of light intensity was analysed in plants grown under a short-day photoperiod at the growth stage 1.14. Plants were acclimated at 4 °C for seven days under 100 and 20 μmol m-2s-1 PPFD for control and limited-light conditions, respectively. All cold acclimated plants accumulated molecular markers reportedly associated with acquired freezing tolerance, including proline, sucrose, CBFs, and COR gene protein products dehydrins and low-temperature-responsive proteins LTIs. Observed changes indicated that low PPFD did not inhibit the cold acclimation process, and the freezing stress experiment confirmed similar survival rates. The molecular analysis found distinct PPFD-specific adaptation mechanisms that were manifested in contrasting content of anthocyanins, cytokinin conjugates, abundances of proteins forming photosystems, and enzymes of protein, energy, and ROS metabolism pathways. Finally, this study led to the identification of putative proteins and metabolite markers correlating with susceptibility to freezing stress of non-acclimated plants grown under low PPFD. Our data show that Arabidopsis plants grown under short-day photoperiod can be fully cold-acclimated under limited light conditions, employing standard and PPFD-specific pathways.
Project description:Cold stress impedes the growth and development of plants, restricts the geographical distribution of plant species, and impacts crop productivity. In this study, we analyzed the Arabidopsis thali-ana transcriptome to identify genes with differential expression (DEGs) in 14-day-old plantlets exposed to temperatures of 0°C, 4°C, and 10°C for 24 h, compared to the 22°C control group. We found 31 genes shared among three low temperatures, with 9 genes common to 0°C-4°C, 8 genes to 4°C-10°C, and 2 genes to 0°C-10°C among the top 50 cold-induced genes from each tempera-ture. Our data revealed that genes, such as galactinol synthase 3 (Gols3, At1g09350), CIR1 (At5g37260), DnaJ (At1g71000), and At5g05220 (unknown function), exhibited the highest ex-pressions at 0°C and 4°C during the 24, 48, and 72-h intervals. We also studied genes from the UDP-glycosyltransferase (UGT78) family, including At5g17030 (D3), At5g17040 (D4), At5g17050 (D2), and At1g30530 (D1), which showed increased expression at low temperatures compared to plantlets at 22°C for 24 h. Gene ontology analysis revealed that DEGs highly en-riched were found in biological processes including “RNA secondary structure unwinding” and “rRNA processing” induced at the three low temperatures, whereas processes related to photo-synthesis were repressed. Our findings indicated upregulation in the expression of four RNA hel-icases (RH13, RH48, RH32, and RH29), belonging to the “RNA secondary structure unwinding” category, mainly at 0°C and 4°C. This study provides valuable information on the molecular mechanisms that activate Arabidopsis thaliana in its early response to these three low tempera-tures.
Project description:Keeping imbibed seeds at low temperatures for a certain period, so called seed vernalization (SV) treatment, promotes seed germination and subsequent flowering in various plants. Vernalization-promoting flowering requires GSH. However, the expression patterns analyzed by GeneChip arrays showed that increased GSH biosynthesis partially mimics SV treatment in Arabidopsis thaliana. SV treatment (keeping imbibed seeds at 4°C for 24 h) induced a specific pattern of gene expression and promoted subsequent flowering in wild-type plants. A similar pattern was observed at 22°C in transgenic plants (35S-GSH1 plants) overexpressing the γ-glutamylcysteine synthetase gene GSH1, coding an enzyme limiting GSH biosynthesis, under the control of the cauliflower mosaic virus 35S promoter. This pattern was strengthened at 4°C but flowering was less responsive to SV treatment. There was a difference in the transcript behaviour of the flowering repressor FLC between wild-type and 35S-GSH1 plants. Unlike other genes responsive to SV treatment, SV-dependent decrease in FLC in wild-type plants was reversed in 35S-GSH1 plants. SV treatment increased GSSG level in wild-type seeds, whereas GSSG level was high in 35S-GSH1 plants, even at a non-vernalizing temperature. Taking into consideration that low temperatures stimulate GSH biosynthesis and bring about oxidative stress, GSSG is considered to trigger low temperature response, but enhanced GSH synthesis was not enough for mimicking SV treatment. To complete it, it essentially required the cellular redox retransition from the oxidized to the reduced state that is observed after the seed vernalization treatment. Four samples (Col-0 and 35S-GSH1 seeds imbibed at 22˚C or 4˚C). Two replicates for each samples.
Project description:To investigate the response of Arabidopsis thaliana plants to non-freezing, cool temperatures, we subjected four week old plants to various chilling temperatures at defined times during the diurnal cycle to control for diurnal effects on transcription. From the same plants, metabolites and enzyme activities were measured as well. Interestingly a gradual change could be observed over a wide range of temperatures. Some of which could be attributed to the CBF program. Experiment Overall Design: Arabidopsis thaliana rosettes from 4 week old plants at a time point four hours into the light-period were transfered to various "chilling" temperatures (20 [control], 17, 14, 12, 10 and 8°C] and harvested after 6 or 78 hours (both 10 hours into the light period). Experiment Overall Design: 6 continuous treatments X 2 timepoints X 2 replicates
Project description:How plants control the transition to flowering in response to ambient temperature is only beginning to be understood. In Arabidopsis thaliana, the MADS-box transcription factor genes FLOWERING LOCUS M (FLM) and SHORT VEGETATIVE PHASE (SVP) have key roles in this process. FLM is subject to temperature-dependent alternative splicing, producing two splice variants, FLM-M-NM-2 and FLM-M-NM-4, which compete for interaction with the floral repressor SVP. The SVP/FLM-M-NM-2 complex is predominately formed at low temperatures and prevents precocious flowering. In contrast, the competing SVP FLM-M-NM-4 complex is impaired in DNA binding and acts as a dominant negative activator of flowering at higher temperatures. Our results demonstrate the importance of temperature-dependent alternative splicing in modulating the timing of the floral transition in response to environmental change. ChIP-seq A. thaliana FLM (3 replicates for gFLM and 2 replicates for FLM splice variants)
Project description:Key genes involved in symbiosis have been lost in nonmycorrhizal plants such as Arabidopsis thaliana. We studied the effects on gene expression in A. thaliana expressing an abbreviated, functional version of one of genes, the transcription factor Interacting Protein of DMI3 (IPD3-min), under low nutrient conditions in the presence and absence of a mycorrhizal fungi, Rhizophagus. We conducted the same transcriptome analysis with a cyclops-4 knockout mutant in Lotus japonicus to compare with the expression profile of a mycorrhizal host model lacking IPD3.