Project description:Autophagy is a conserved process that recycles cellular contents to promote survival. Although nitrogen starvation is the canonical inducer of autophagy, recent studies have revealed several other nutrients important to this process. In this study, we used a quantitative, high-throughput assay to identify potassium starvation as a new and potent inducer of autophagy. We found that potassium-dependent autophagy requires the core pathway kinases Atg1, Atg5, Vps34, as well as other components of Phosphatidylinositol 3-kinase Complex I. Transmission electron microscopy revealed abundant autophagosome formation in response to both stimuli. RNA sequencing indicated distinct transcriptional responses – nitrogen affects transport of ions such as copper while potassium targets the organization of other cellular components. Thus, nitrogen and potassium share the ability to influence metabolic supply and demand but do so in different ways. Both inputs promote catabolism through bulk autophagy, but inhibit cellular anabolism through distinct mechanisms.
Project description:In this study we investigated the transcriptional response of the yeast Saccharomyces cerevisiae to potassium starvation. To this end yeast cells were grown for 60 min in media without potassium or in media with a standard potassium concnetration (50 mM KCl). Using Serial Analysis of Gene Expression (SAGE)-tag sequencing the effect of potassium starvation on the transcriptome was determined.
Project description:In this study we investigated the transcriptional response of the yeast Saccharomyces cerevisiae to potassium starvation. To this end yeast cells were grown for 60 min in media without potassium or in media with a standard potassium concnetration (50 mM KCl). Using Serial Analysis of Gene Expression (SAGE)-tag sequencing the effect of potassium starvation on the transcriptome was determined. 4 samples of cells grown in media without potassium and 4 samples of cells grown in the presence of potassium were analyzed.
Project description:We investigated the transcriptional response of yeast Saccharomyces cerevisiae bmh1 and bmh2 deletion mutants to potassium starvation. To this end yeast strains were grown for 60 min in media without potassium or in media with a standard potassium concentration (50 mM KCl). Using Serial Analysis of Gene Expression (SAGE)-tag sequencing the effect of potassium starvation on the transcriptome was determined. This study is a follow-up of our previous study (Anemaet IG and van Heusden GPH. 2014. BMC Genomics:1040)( GEO accession number GSE57093).
Project description:This experiment was annotated by TAIR (http://arabidopsis.org). This experiment studies the response of gene expression in roots of 25-35 day old plants grown on hydroponics after 6, 48 and 96 hours of potassium starvation. RNA from roots was extracted after transfer to control (control) or potassium free nutrient solution respectively (starvation). Experimenter name = Julian Schroeder Experimenter phone = 619-534-7759 Experimenter fax = 619-534-7108 Experimenter department = J Schroeder Laboratory Experimenter institute = University of California-San Diego Experimenter address = Biology Department Experimenter address = University of California-San Diego Experimenter address = La Jolla Experimenter zip/postal_code = CA 92093-0116 Experimenter country = USA Keywords: time_series_design; growth_condition_design
Project description:Autophagy is the primary catabolic process triggered in response to starvation. Although autophagic regulation within the cytosolic compartment is well established, it is becoming clear that nuclear events also regulate the induction or repression of autophagy. Nevertheless, a thorough understanding of the mechanisms by which sequence-specific transcription factors modulate expression of genes required for autophagy is lacking. Here, we identify Foxk proteins (Foxk1 and Foxk2) as transcriptional repressors of autophagy in muscle cells and fibroblasts. Interestingly, Foxk1/2 serve to counter-balance another forkhead transcription factor, Foxo3, which induces an overlapping set of autophagic and atrophic targets in muscle. Foxk1/2 specifically recruits Sin3A-HDAC complexes to restrict acetylation of histone H4 and expression of critical autophagy genes. Remarkably, mTOR promotes the transcriptional activity of Foxk1 by facilitating nuclear entry to specifically limit basal levels of autophagy in nutrient-rich conditions. Our study highlights an ancient, conserved mechanism whereby nutritional status is interpreted by mTOR to restrict autophagy by repressing essential autophagy genes via Foxk-Sin3-mediated transcriptional control. Examination of (1) chromatin binding of Foxk1 and Sin3A in non-starved myoblasts and (2) gene expression profiling upon either starvation or siRNA-mediated depletion of Foxk1 relative to a non-starved control.
Project description:Ectomycorrhizal fungi are dependent on host trees for carbon supply. In return ectomycorrhizal fungi supply trees with water and nutrients. It is known that when ectomycorrhizal fungi have exploited a nutrient rich patch in soil, the carbon allocation to mycelia in that patch is reduced, with the consequence of mycelia dying, but less is known of the dynamics of this senescence. We cultivated the ectomycorrhizal fungus Paxillus involutus in an axenic system. We collected growth and transcriptome data at different stages of carbon starvation during fungal growth. Carbon starvation induced a decrease in fungal biomass, which coincided with the release of NH4+ and the expression of genes connected with autophagy as well as protease and chitinase activity. Monoaromatic compounds, chitin and protease activity was detected in the liquid growth media during carbon starvation. The exudation of NH4+ and increase of monoaromatic compound during C starvation suggests senescence and autolysis of P. involutus. Together with the upregulation of genes involved in autophagy, chitinase and endopeptidase activity this points towards a controlled senescence including recycling of compounds originating from the fungi. Reduced C allocation to ectomycorrhizal mycelia in recently depleted nutrient patches in forest soils must be of ubiquitous nature. Understanding the mechanisms during exploitation of nutrients by ectomycorrhizal fungi is of great importance for understanding carbon and nutrient dynamics in forest soils. This is to our knowledge the first study describing the carbon starvation response in an ectomycorrhizal fungus. A one-chip study (data from 12 subarrays collected from a 12-plex Nimblegen microarray (ID 527890) using total RNA recovered from three separate glass-bead cultures of Paxillus involutus (ATCC200175) grown on Minimum Melin Norkrans medium (MMN) amended with ammonium (C/N ratio 3) and harvested at different times of carbon starvation.)
Project description:This experiment was annotated by TAIR (http://arabidopsis.org). This experiment studies the response of gene expression in roots of 25-35 day old plants grown on hydroponics after 6, 48 and 96 hours of potassium starvation. RNA from roots was extracted after transfer to control (control) or potassium free nutrient solution respectively (starvation). Experimenter name = Julian Schroeder; Experimenter phone = 619-534-7759; Experimenter fax = 619-534-7108; Experimenter department = J Schroeder Laboratory; Experimenter institute = University of California-San Diego; Experimenter address = Biology Department; Experimenter address = University of California-San Diego; Experimenter address = La Jolla; Experimenter zip/postal_code = CA 92093-0116; Experimenter country = USA Experiment Overall Design: 4 samples were used in this experiment
Project description:Ectomycorrhizal fungi are dependent on host trees for carbon supply. In return ectomycorrhizal fungi supply trees with water and nutrients. It is known that when ectomycorrhizal fungi have exploited a nutrient rich patch in soil, the carbon allocation to mycelia in that patch is reduced, with the consequence of mycelia dying, but less is known of the dynamics of this senescence. We cultivated the ectomycorrhizal fungus Paxillus involutus in an axenic system. We collected growth and transcriptome data at different stages of carbon starvation during fungal growth. Carbon starvation induced a decrease in fungal biomass, which coincided with the release of NH4+ and the expression of genes connected with autophagy as well as protease and chitinase activity. Monoaromatic compounds, chitin and protease activity was detected in the liquid growth media during carbon starvation. The exudation of NH4+ and increase of monoaromatic compound during C starvation suggests senescence and autolysis of P. involutus. Together with the upregulation of genes involved in autophagy, chitinase and endopeptidase activity this points towards a controlled senescence including recycling of compounds originating from the fungi. Reduced C allocation to ectomycorrhizal mycelia in recently depleted nutrient patches in forest soils must be of ubiquitous nature. Understanding the mechanisms during exploitation of nutrients by ectomycorrhizal fungi is of great importance for understanding carbon and nutrient dynamics in forest soils. This is to our knowledge the first study describing the carbon starvation response in an ectomycorrhizal fungus.