Post-translational regulation of photosynthetic activity via the TOR kinase in plants.
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ABSTRACT: Chloroplasts are the powerhouse of the plant cell, and their activity must be matched to plant growth to avoid photo-oxidative damage. We have identified a post-translational mechanism linking the conserved Target of Rapamycin (TOR) kinase that promotes growth and the guanosine tetraphosphate (ppGpp) signaling pathway that regulates chloroplast activity, and photosynthesis in particular. We find that RelA SpoT Homologue 3 (RSH3), a nuclear-encoded enzyme responsible for ppGpp biosynthesis, interacts directly with the TOR complex via a plant-specific N-terminal region which is phosphorylated in a TOR-dependent manner. Downregulating TOR activity increases ppGpp synthesis by RSH3, and reduces photosynthetic capacity. The TOR-RSH3 signaling axis therefore regulates chloroplast activity to match plant growth, and sets a new precedent for the regulation of organellar function by TOR.
Project description:The target of rapamycin (TOR) kinase is a central regulatory hub that translates environmental and nutritional information into permissive or restrictive growth decisions. Although the TOR pathway is conserved among eukaryotes, plants developed unique adaptations to this pathway to cope with their autotrophic and sessile nature. Here, we captured for the first time a proteome-wide view of the plant TOR phosphorylation and interaction landscape. After sampling four biological repeats, proteins were extracted, digested and phosphopeptides were enriched. In total, 8302 phosphopeptides on 2558 proteins were identified from all samples. After label free quantitative analysis, a filtered dataset of 5500 phosphopeptides on 2056 proteins was retained. To identify TOR-dependent sites, the control-, AZD8055- and rapamycin-treated samples were statistically analyzed using a linear mixed model to evaluate the effect of the treatment, time and the interaction between both. For T10, T20 and T40, the sucrose control samples were compared to the AZD8055 or rapamycin samples. In addition, the AZD8055 samples were compared to the rapamycin samples, and the sucrose control samples (T10, T20, T40) were compared to T0. Overall, the strongest effect occurred with AZD8055. Therefore, an additional filter was applied retrieving only phosphopeptides that changed at least two-fold upon AZD8055 treatment. In total, 96 unambiguous TOR-dependent phosphosites were detected on 66 proteins, linking TOR to a plethora of biological processes.
Project description:The Tor kinase is one of the major regulatory nodes in a eukaryotic cell and until now, little is known about this kinase in filamentous fungi. Here, we analysed the Tor kinase in Aspergillus fumigatus, which is the most important airborne fungal pathogen of humans and the main causative agent of invasive aspergillosis. Because deletion of the single tor gene of A. fumigatus was apparently lethal, we generated a conditional lethal tor mutant. This was achieved by fusing the tor gene with the inducible xylose promoter and replacing the endogenous tor gene by the inducible xylp-tor gene cassette. The generated transgenic strain opened up the possibility to activate or silence the tor gene under controlled conditions. Since we did not observe any effect of rapamycin on Tor of A. fumigatus, the generation of the inducible Tor gene was even more valuable for an in-depth analysis of the Tor kinase. By LC-MS/MS analyses of mycelial proteins we identified the regulatory network of Tor. Tor controls a variety of genes and proteins involved in nutrient sensing, stress response, cell cycle progression, protein biosynthesis and degradation. Tor is a major kinase responsible for protein import into the mitochondria, and consequently responsible for the correct function of most processes occurring into these organelles, e.g. respiration and ornithine metabolism. Regulation of iron acquisition by Tor was found to be independent of the HapX transcription factor.
Project description:The Spi1/ Pu.1 transcription factor plays a crucial role in myeloid cell development across many species. Several Spi1 target genes have been identified so far, yet the Spi1-dependent gene group remains largely unknown. To identify novel genes downstream of Spi1 we employed a microarray strategy using zebrafish embryos. We established the gene group down-regulated upon spi1 knockdown while simultaneously enriched in FACS-sorted embryonic myeloid cells of a spi1:GFP transgenic line, thus representing putative myeloid-specific Spi1 target genes. This gene group contained all previously identified Spi1-dependent zebrafish genes, confirming the validity of the approach, as well as novel immune-related genes. Colocalization studies with neutrophil and macrophage markers revealed that genes cxcr3.2, mpeg1, ptpn6 and mfap4 were expressed specifically in early embryonic macrophages. The analysis of adult zebrafish hematopoietic tissue showed that genes mfap4 and mpeg1 remained macrophage specific within the myeloid fraction throughout zebrafish life. We also demonstrated that gene cxcr3.2, coding for chemokine receptor 3.2, functions in macrophage migration to the site of bacterial infection. These results establish a myeloid-specific gene group dependent on Spi1 in zebrafish and identify novel early macrophage-specific marker genes, which will facilitate further studies of macrophage development and innate immune function. Zebrafish strains Zebrafish (Danio rerio) were handled in compliance with the local animal welfare regulations and maintained according to standard protocols (http://ZFIN.org). The spi1-gfp transgenic line used in this study (Pu1-lynEGFP, a gift from Franscesca Peri, EMBL, Heidelberg) contains 4 kb of spi1/pu.1 promoter sequence driving expression of membrane-targeted EGFP. Morpholino knock-down experiments Morpholino oligonucleotides (Gene Tools) were diluted to required concentration in 1x Danieu’s buffer (58 mM NaCl, 0.7 mM KCl, 0.4 mM MgSO4, 0.6 mM Ca(NO3)2, 5.0 mM HEPES; pH 7.6) containing 1% Phenol red (Sigma) and approximately 1 nl was injected into the 1-2 cell stage embryo using a Femtojet injector (Eppendorf). Embryo dissociation and FACS (Fluorescent activated cell sorting) Dissociation of embryos was performed according to Covassin et al. 30. In short, ~300 embryos of spi1:GFP line at 28 hpf were dechorionated by pronase treatment, rinsed in calcium free Ringer solution, followed by digestion with 0.25% trypsin. The obtained cell suspension was centrifuged, rinsed with PBS and resuspended in Leibovitz medium L15 without phenol red, 1% fetal calf serum, 0.8mM CaCl2, penicillin 50 U/ml and streptomycin 0.05 mg/ml. The single cell suspension was subject to FACS at room temperature using a FACSAria (Becton Dickinson) with the BD FACSDiva software version 5.0.3 and a Coherent Sapphire solid state laser 488 nm with 13 mW power. The GFP+ and GFP- cell fractions were collected separately into L15 medium supplemented with 0.8 mM CaCl2, 10% fetal calf serum and penicillin 50 U/ml and streptomycin 0.05 mg/ml. The standard yield from circa 300 embryos was approximately 2 x 105 GFP+ cells. Microarray experiment design and analysis Embryos injected either with 1 mM Pu1 morpholino19 or 1 mM Standard Control morpholino were harvested at 28 hours post fertilization (hpf). As a control, embryos injected with an equal volume of 1% Phenol red in Danieu’s buffer (1xPR/D) were used. Pools of 20-30 embryos were collected. RNA samples from spi1 morphants and standard control morphants were labelled with Cy5 and hybridized against a Cy3-labelled common reference (a mixture of all samples injected with 1xPR/D). This experiment was performed in triplicate. FACS sorted spi1-GFP zebrafish embryos at 28hpf were analyzed as follows: the RNA of GFP-positive fraction was labelled with Cy5 and hybridized against a Cy3-labelled RNA of corresponding GFP-negative fraction of cells from the same pool of embryos. This experiment was performed in duplicate. RNA isolation, synthesis of amino allyl labeled aRNA, coupling of Cy3 and Cy5 dyes, and hybridization conditions were as described31. Microarray analysis was performed using custom-designed 44k Agilent chips (platform accession number in GEO: GPL7735) described elsewhere 31. Microarray data were processed and analyzed as described 31. Significance cut-offs for differentially expressed probe sequences were set at 1.2 fold change at P <10-2.
Project description:Nitrogen (N) is of utmost importance for plant growth and development. Multiple studies have shown that N signaling is tightly coupled with carbon (C) levels, but the interplay between C/N metabolism and growth remains largely an enigma. Nonetheless, the protein kinases sucrose non-fermenting 1 (SNF1)-related kinase 1 (SnRK1) and target of rapamycin (TOR), two ancient central metabolic regulators, are emerging as key integrators that link C/N status with growth. Despite their pivotal importance, the exact mechanisms behind the sensing of N status and its integration with C availability to drive metabolic decisions are largely unknown. Especially for SnRK1 it is not clear how this kinase responds to altered N levels. Therefore, we first monitored N-dependent SnRK1 kinase activity at high resolution with our in vivo separation of phase-based activity reporter of kinase (SPARK), revealing a contrasting N-dependency in shoot and root tissues. Next, using affinity purification (AP) and proximity labeling (PL) coupled to mass spectrometry (MS) experiments, we constructed an N-specific SnRK1 and TOR interactome in Arabidopsis thaliana cell cultures during N-starved and repleted growth conditions. To broaden our understanding of the N-dependency of the TOR/SnRK1 signaling pathway, the resulting network was compared to corresponding C-related networks, identifying a large number of novel, N-specific interactors. Moreover, through integration of N dependent transcriptome and phosphoproteome data, we were able to pinpoint additional N dependent network components, revealing SnRK1 regulatory proteins that might function at the crosstalk of C/N signaling. Finally, confirmation of known and identification of novel interactors, such as IRE1A and RAB18, indicate that the endoplasmic reticulum functions as a key regulatory hub for TOR and SnRK1 via integration of C/N signaling.
Project description:While significant advances have been made in EHEC pathogenesis, we still do not fully understand the impact of environmental stress on EHEC virulence. During the course of infection, EHEC must evade or overcome several biological barriers, the first of which is the gastric acidity encountered during passage through the stomach. EHEC is remarkable in its ability to tolerate this acidity. There are four different acid resistance systems that provide E. coli O157:H7 protection against exposure to low pH (2-2.5). Interestingly, EHEC uses these acid resistance systems differentially for survival in foods versus the bovine intestinal tract. The glutamate-dependent acid-resistance system is thought to offer the best protection below pH 3. Since the infectious dose of EHEC is so low (50-100 organisms), acid resistance becomes an important virulence trait. Studies of EHEC response to acid stress have focused primarily on levels of acid tolerance and the molecular basis of tolerance. However, the impact of acid stress on EHEC virulence is less well understood. In the related pathogen, EPEC, the plasmid-encoded regulator, Per, that regulates expression of many EPEC virulence factors, is regulated negatively at pH 5.5 and positively at pH 8.0, suggesting that virulence gene expression is repressed during mild acid stress and enhanced in alkaline pH typical of the small intestine. Expression of EPEC type III secreted factors involved in A/E lesion formation has been shown to be influenced by factors including culture media, iron and calcium levels. Protein secretion was inhibited at pH 6 and 8. In a third study, a gadE (encoding acid resistance regulator) mutation resulted in increased adhesion of E.coli O157:H7 to colonic epithelial cells, suggesting negative regulation of one or more adhesins. Other studies have reported that shiga toxin production is sensitive to culture conditions including pH. However, there are no studies of EHEC virulence changes after more severe acid stress nor studies linking stressed EHEC virulence phenotype with transcriptional changes. The goal of this study was to determine how acid stress affects EHEC virulence properties and through microarray analysis, define the genetic basis for these changes. Understanding how acid stress modulates the virulence potential of this pathogen is essential for delineating the pathogenesis of disease caused by EHEC infection and may offer novel approaches to prevent and treat EHEC infections. Bacteria were grown in LB broth overnight, then subcultured into DMEM and grown at 37C, 5%Co2. Bacteria were then subjected to one of three acid stress protocols: 1) UA30: growth in DMEM pH 7.4 followed by growth in DMEM pH 3.0 for 30 minutes; 2) AA30: growth in DMEM pH 5.0 (adaptation) followed by growth in DMEM pH 3.0; 3) UA15: growth in DMEM pH 7.4 followed by growth in DMEM pH 3.0 for 15 minutes. DMEM was supplemented with 25 mM MES (pH 5.0) and in the case of the control (unadapted, unshocked) 25 mM MOPS (pH 7.4) and the adaptation step was again carried out at 37C and 5% CO2. Acid shocking was done at pH 3.0 (unbuffered) at room temperature for all treatments
Project description:Using DNase-seq, mRNA-seq and publicly available ChIP-seq data sets, we examined the role of chromatin accessibility (DNase-seq) in androgen receptor binding to the genome (ChIP-seq) and AR-mediated transcriptional changes (mRNA-seq). Our data reveals genome-wide changes in chromatin structure that correspond to AR binding and differential gene expression. A focused examination of DNase-seq data around androgen receptor motifs within androgen receptor ChIP-seq peaks reveals distinct patterns of protection from DNaseI cleavage. Examination of chromatin accessibility (DNase-seq), AR binding (AR ChIP-seq), and transcription (mRNA-seq) in LNCaP cells before and after 12 hours of 1 nM R1881 treatment This Series represents the RNA-Seq data only. Exon microarray data generated under the same conditions is available through GSE15805. The DNase-seq data is publicly available through GSE32970 as well as the UCSC genome browser (genome.ucsc.edu) under Regulation::ENCODE DNase/FAIRE::Duke DNaseI HS:LNCaP and LNCaP + Andro. The accession numbers for the ChIP-seq experiments used are GSE14097 and GSE28126.
Project description:Rapamycin is an inhibitor of the evolutionary conserved Target of Rapamycin (TOR) kinase which promotes and coordinates translation with cell growth and division. In heterotrophic organisms, TOR regulation is based on intra- and extracellular stimuli such as amino acids level and insulin perception. However, how plant TOR pathways have evolved to integrate plastid endosymbiosis is a remaining question. Despite the close association of the TOR signaling with the coordination between protein turn-over and growth, proteome and phosphoproteome acclimation to a rapamycin treatment have not yet been thoroughly investigated in Chlamydomonas reinhardtii. In this study, we have used in vivo label-free phospho-proteomic analysis to profile both protein and phosphorylation changes at 0, 24, and 48 h in Chlamydomonas cells treated with rapamycin. Using multivariate statistics we highlight the impact of TOR inhibition on both the proteome and the phosphoproteome. Two-way ANOVA distinguished differential levels of proteins and phosphoproteins in response either to culture duration and rapamycin treatment or combined effects. Finally, protein– protein interaction networks and functional enrichment analysis underlined the relation between plastid and mitochondrial metabolism. Prominent changes of proteins involved in sulfur, cysteine, and methionine as well as nucleotide metabolism on the one hand, and changes in the TCA cycle on the other highlight the interplay of chloroplast and mitochondria metabolism. Furthermore, TOR inhibition revealed changes in the endomembrane trafficking system. Phosphoproteomics data, on the other hand, highlighted specific differentially regulated phosphorylation sites for calcium-regulated protein kinases as well as ATG7, S6K, and PP2C. To conclude we provide a first combined Chlamydomonas proteomics and phosphoproteomics dataset in response to TOR inhibition, which will support further investigations.
Project description:We provide evidence of the generation of Rdp1-mediated secondary siRNAs in vivo in fission yeast. Secondly, we show that the presence of Ago1-associated siRNAs does not guarantee robust silencing. We obtained sequences from gel purified small RNAs of wt and rdp1delta fission yeast cells and FLAG-ago1 associated small RNAs.
Project description:To unravel the potential cooperative roles of oxygen-regulated signaling pathways; von Hippel-Lindau (VHL) tumor suppressor protein and hypoxia-inducible factor (HIF) transcription factors, we have generated mutant mice with; Vhlh, Vhlh/Hif1α, Vhlh/Hif2α and Vhlh/Hif1α/Hif2α gene alleles floxed. Subsequently primary kidney cells were isolated, cultured and infected with Adenoviruses bearing either Cre/GFP or GFP expression only. Agilent cDNA microarrays were utilized to compare the gene expression profiles of the kidney epithelial cells from aforementioned cell cultures to gain insight about the molecules and signaling pathways that drive aberrant cellular proliferation in clear cell renal cell carcinoma (ccRCC). 24 independent biological samples from 4 genetic experimental conditions were hybridized in two- color format on 13 Mouse GE 4x44K v2 Microarray Kit (Design ID 026655) arrays. Eventual dye specific hybridization effects were controlled with dye swap on biological replicates. For an each experimental condition 3 arrays were use, except of one where 4 arrays were used (one sample combination in repetition with a dye swap). For the final analysis the gene expression levels were dye effect corrected and values for biological replicates were averaged to obtain a matrix with gene expression levels for 4 independent biological (1. Vhlh-/-, 2. Vhlh-/-/Hif1α-/-, 3. Vhlh-/-/Hif2α-/- and 4. Vhlh-/-/Hif1α-/-/Hif2α-/-) conditions.
Project description:Bud dormancy is a critical developmental process for perennial plant survival, and also an important physiological phase that affects the next seasonM-bM-^@M-^Ys growth of temperate fruit trees. Bud dormancy is regulated by multiple genetic factors, and affected by various environmental factors, tree age and vigor. To understand molecular mechanism of bud dormancy in Japanese apricot (Prunus mume Sieb. et Zucc.), we constructed a custom oligo DNA microarray covering the Japanese apricot dormant bud ESTs referring to peach (P. persica) genome sequence. Because endodormancy release is a chilling temperature-dependent physiological event, genes showing chilling-mediated differential expression patterns are candidates to control endodormancy release. Using the microarray constructed in this study, we monitored gene expression changes of dormant vegetative buds of Japanese apricot during prolonged artificial chilling exposure. In addition, we analyzed seasonal gene expression changes. M-bM-^@M-^XNankoM-bM-^@M-^Y vegetative buds collected in November, and those exposed to chilling for 40 or 60 days were used as microarray samples. Among the 58539 different unigene probes, 2345 and 1059 genes were identified as being more than two-fold up-regulated and down-regulated, respectively, following chilling exposure for 60 days (P value < 0.05). The down-regulated genes included P. mume DORMANCY-ASSOCIATED MADS-box genes, which supported the previous quantitative RT-PCR and EST analyses showing that these genes are repressed by prolonged chilling treatments. The genes encoding lipoxygenase were remarkably up-regulated by prolonged chilling. Cluster analysis suggested that the expression of the genes showing expression changes by artificial chilling exposure were coordinately regulated by seasonal changes. Our parametric analysis of gene set enrichment suggested that genes related to jasmonic acid (JA) and oxylipin biosynthesis and metabolic processes were significantly up-regulated by prolonged chilling, whereas genes related to circadian rhythm were significantly down-regulated. The results obtained from the microarray analyses were verified by quantitative RT-PCR analysis of selected genes. Taken together, this study raised the possibility that the microarray platform constructed in this study is applicable for deeper understanding of molecular network related to agronomically important bud phisiologies including dormancy release. In this study, we used chilling exposed bud samples (0, 40, 60 days starting at November) and seasonal monthly bud samples (June to March). For the samples in dataset 1 (three different time points during chilling treatment), three technical replicates (60K M-CM-^W 3 per sample) with three biological replicates were averaged, whereas three technical replicates were averaged for the samples in dataset 2 (10 different seasonal time points)