Project description:During cold acclimation plants increase their freezing tolerance in response to low non-freezing temperatures. This is accompanied by many physiological, biochemical and molecular changes that have been extensively investigated. In addition, many cold acclimated plants become more freezing tolerant during exposure to mild, non-damaging sub-zero temperatures. There is hardly any information available about the molecular basis of this adaptation. However, Arabidopsis thaliana is among the species that acclimate to sub-zero temperatures. This makes it possible to use the molecular and genetic tools available in this species to identify components of sub-zero signal transduction and acclimation. Here, we have used microarrays and a qRT-PCR primer platform covering 1880 genes encoding transcription factors to monitor changes in gene expression in the accessions Columbia-0, Rschew and Tenela during the first three days of sub-zero acclimation at -3°C. The results indicate that gene expression during sub-zero acclimation follows a tighly controlled time-course. Especially AP2/EREBP and WRKY transcription factors may be important regulators of sub-zero acclimation, although the CBF signal transduction pathway seems to be less important during sub-zero than during cold acclimation. Globally, we estimate that approximately 5% of all Arabidopsis genes are regulated during sub-zero acclimation. Particularly photosynthesis-related genes were down-regulated and genes belonging to the functional classes of cell wall biosynthesis, hormone metabolism and RNA regulation of transcription were up-regulated. Collectively, these data provide the first global analysis of gene expression during sub-zero acclimation and allow the identification of candidate genes for forward and reverse genetic studies into the molecular mechanisms of sub-zero acclimation. We used whole genome microarrays to monitor changes in gene expression in the Arabidopsis thaliana accessions Columbia-0, Rschew and Tenela during three days of acclimation to sub-zero temperature at -3°C after cold acclimation

Project description:During cold acclimation plants increase their freezing tolerance in response to low non-freezing temperatures. This is accompanied by many physiological, biochemical and molecular changes that have been extensively investigated. In addition, many cold acclimated plants become more freezing tolerant during exposure to mild, non-damaging sub-zero temperatures. There is hardly any information available about the molecular basis of this adaptation. However, Arabidopsis thaliana is among the species that acclimate to sub-zero temperatures. This makes it possible to use the molecular and genetic tools available in this species to identify components of sub-zero signal transduction and acclimation. Here, we have used microarrays and a qRT-PCR primer platform covering 1880 genes encoding transcription factors to monitor changes in gene expression in the accessions Columbia-0, Rschew and Tenela during the first three days of sub-zero acclimation at -3°C. The results indicate that gene expression during sub-zero acclimation follows a tighly controlled time-course. Especially AP2/EREBP and WRKY transcription factors may be important regulators of sub-zero acclimation, although the CBF signal transduction pathway seems to be less important during sub-zero than during cold acclimation. Globally, we estimate that approximately 5% of all Arabidopsis genes are regulated during sub-zero acclimation. Particularly photosynthesis-related genes were down-regulated and genes belonging to the functional classes of cell wall biosynthesis, hormone metabolism and RNA regulation of transcription were up-regulated. Collectively, these data provide the first global analysis of gene expression during sub-zero acclimation and allow the identification of candidate genes for forward and reverse genetic studies into the molecular mechanisms of sub-zero acclimation. We used whole genome microarrays to monitor changes in gene expression in the Arabidopsis thaliana accessions Columbia-0, Rschew and Tenela during three days of acclimation to sub-zero temperature at -3°C after cold acclimation Plants from Arabidopsis thaliana accessions Columbia-0, Rschew and Tenela were cold acclimated at 4°C for two weeks. Detached leaves were then sub-zero acclimated at -3°C for 8 h, 1 d or 3 d at -3°C. Leaves of cold acclimated plants and sub-zero acclimated leaves were collected for RNA extraction and hybridization on Affymetrix ATH1 microarrays in order to explore temporal transcriptome changes during sub-zero acclimation. For each sample total RNA was isolated from a pool of three leaves from three different plants. The experiment was performed in three idenpendent biological replicates.

Project description:Gall formation on the belowground parts of plants infected with Plasmodiophora brassicae is the result of extensive host cellular reprogramming. The development of these structures is a consequence of increased cell proliferation followed by massive enlargement of cells colonised with the pathogen. Drastic changes in cellular growth patterns create local deformities in the roots and hypocotyl giving rise to mechanical tensions within the tissue of these organs. Host cell wall extensibility and recomposition accompanies growth of the gall, influences pathogen spread and also pathogen life cycle progression. Demethylation of pectin within the extracellular matrix may play an important role in P. brassicae-driven hypertrophy of host underground organs. Through proteomic analysis of the cell wall we identified proteins accumulating in the galls developing on the underground parts of Arabidopsis thaliana plants infected with P. brassicae. One of the key proteins identified was the pectin methylesterase PME18; we further characterised its expression and conducted functional and anatomic studies in the knock-out mutant and used Raman spectroscopy to study the status of pectin in P. brassicae infected galls. We found that late stages of gall formation are accompanied with increased levels of Pectin Methylesterase 18 (PME18). We have also shown, that the massive enlargement of cells colonised with P. brassicae coincides with decreases in pectin methylation. In pme18-1 knock-out mutants P. brassicae could still induce demethylation; however, the galls in this line were smaller and cellular expansion was less pronounced. Alteration in pectin demethylation in the host resulted in changes in pathogen distribution and slowed down disease progression. To conclude, P. brassicae driven host organ hypertrophy observed during clubroot disease is accompanied by pectin demethylation in the extracellular matrix. The pathogen hijacks endogenous host mechanisms involved in cell wall loosening to create an optimal cellular environment for completion of its life cycle and eventual release of resting spores facilitated by degradation of demethylated pectin polymers.

			Action	DRS
	CC series.pride.mgf.gz	Mgf
	CC1.raw	Raw
	CC10.raw	Raw
	CC11.raw	Raw
	CC12.raw	Raw

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Both cold and sub-zero acclimation induce cell wall modification and changes in the extracellular proteome in Arabidopsis thaliana

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Both cold and sub-zero acclimation induce cell wall modification and changes in the extracellular proteome in Arabidopsis thaliana.

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