Transcriptional profiles between mp mutant seedlings and transgenics carrying the dexamethasone-inducible GR-bdl protein
ABSTRACT: In order to identify targets of the transcription factor AUXIN RESPONSE FACTOR5 / MONOPTEROS (ARF5/MP), we compared transcriptomes of mp-B4149 mutant seedlings (9 day-old) and seedlings carrying the dexamethasone-inducible version of the MP inhibitor protein BODENLOS (GR-bdl). Without dexamethasone (DEX) treatment, this line is identical to the wild-type, while DEX treatment leads to strong inhibition of ARF-dependent transcription. To remove all endogenous MP-inhibiting Aux/IAA proteins, we treated mp or GR-bdl seedlings during 1 hour with auxin (50 micromolar Indole-3-Acetic Acid), either with or without a pretreatment with 10 micromolar DEX for 1 hour. Genes that are activated by MP are expected to br downregulated in mp seedlings and in the GR-bdl line afer DEX treatment. We used biological duplicates for each of the three treatments. Keywords: Transcriptional profiling of transcription factor targets Overall design: Mp mutant and GR-bdl seeds were germinated on solid 1/2MS media, and transferred to liquid medium after 9 days of horizontal growth. Duplicate cultures were generated for mp mutants, and quadruplicates for the GR-bdl line. 10 micromolar DEX was added to both mp cultures and to two of the GR-bdl cultures, and seedlings were gently shaken during 1 hour. Then, 50 micromolar IAA was added to all 6 cultures and seedlings were incubated with gentle shaking for another hour. Total RNA was isolated from the seedlings using a QIAgen RNeasy kit, and reverse transcription, in-vitro transcription, cRNA labling and fragemntation was done according to established methods (Schmid et al., Nature Genetics  37, 501-506). Labeled cRNA was hybridized to Arabidopsis ATH1 arrays.
Project description:In order to identify targets of the transcription factor AUXIN RESPONSE FACTOR5 / MONOPTEROS (ARF5/MP), we compared transcriptomes of mp-B4149 mutant seedlings (9 day-old) and seedlings carrying the dexamethasone-inducible version of the MP inhibitor protein BODENLOS (GR-bdl). Without dexamethasone (DEX) treatment, this line is identical to the wild-type, while DEX treatment leads to strong inhibition of ARF-dependent transcription. To remove all endogenous MP-inhibiting Aux/IAA proteins, we treated mp or GR-bdl seedlings during 1 hour with auxin (50 micromolar Indole-3-Acetic Acid), either with or without a pretreatment with 10 micromolar DEX for 1 hour. Genes that are activated by MP are expected to br downregulated in mp seedlings and in the GR-bdl line afer DEX treatment. We used biological duplicates for each of the three treatments. Keywords: Transcriptional profiling of transcription factor targets Mp mutant and GR-bdl seeds were germinated on solid 1/2MS media, and transferred to liquid medium after 9 days of horizontal growth. Duplicate cultures were generated for mp mutants, and quadruplicates for the GR-bdl line. 10 micromolar DEX was added to both mp cultures and to two of the GR-bdl cultures, and seedlings were gently shaken during 1 hour. Then, 50 micromolar IAA was added to all 6 cultures and seedlings were incubated with gentle shaking for another hour. Total RNA was isolated from the seedlings using a QIAgen RNeasy kit, and reverse transcription, in-vitro transcription, cRNA labling and fragemntation was done according to established methods (Schmid et al., Nature Genetics  37, 501-506). Labeled cRNA was hybridized to Arabidopsis ATH1 arrays.
Project description:The WOX1 transcription factor is a multifunctional regulator of lateral-organ development that acts as a transcriptional repressor. WOX1 promotes lamina growth, controls marginal tissue differentiation and is involved in establishment and maintenance of the adaxial-abaxial pattern from the middle domain of leaf primordia. To identify the WOX1 downstream genes, we performed a microarray analysis of shoot apices of transgenic Arabidopsis thaliana lines harboring 35S::WOX1:glucocorticoid receptor (GR) in which the WOX1 function was temporarily enhanced by dexamethasone (DEX). Overall design: The effects of transient enhancement of WOX1 function on shoot apices of seedlings were analyzed by using GR-DEX system. Plants were grown on solid medium contains 0.5x Murashige and Skoog (MS) salts, 1% sucrose, 0.05% MES-KOH (w/v) pH 5.7, 1.2 % purified agar for 6 days and transfer to liquid medium containing 0.5x MS salts, 1% sucrose and 0.05% MES-KOH (w/v) pH 5.7 with or without 10 µM DEX, 10 µM cycloheximide (CHX) and 20 µM IAA. Samples were treated with DEX, CHX and IAA treatments for 6 hours, 6 hours and 3 hours, respectively, before collection. RNA samples were extracted from shoot apices, including leaf primordia, of 6-day post sowing seedlings by using Plant RNeasy Mini Kit (QIAGEN). For analysis of 35S::WOX1:GR plants treated with or without DEX and/or CHX, sampling was performed twice in two independent lines. For analysis of 35S::GFP:GR and of a combined application of DEX and IAA, sampling was performed from two independent lines.
Project description:BACKGROUND:LEAFY COTYLEDON 2 (LEC2) acts throughout embryo morphogenesis and maturation phase to maintain embryogenic identity. Our previous study stated that Arabidopsis thaliana LEC2 (AtLEC2) driven by glucocorticoid receptor-dexamethasone (GR-DEX) inducible system (AtLEC2-GR) triggers embryogenic callus formation in tobacco (Nicotiana tabacum). RESULTS:In this study, the adenosine phosphate isopentenyltransferase genes AtIPT3, AtIPT7 and the tRNA isopentenyltransferase gene AtIPT9 were overexpressed in the AtLEC2-GR transgenic background. In the AtIPT7-OE AtLEC2-GR and AtIPT9-OE AtLEC2-GR seedlings, high-quality embryogenic callus was obtained under the DEX condition, and the shoot regeneration efficiency was 2 to 3.5 folds higher than AtLEC2-GR alone on hormone free medium without DEX. Transcriptome analyses showed that up-regulated BBM, L1L, ABI3, and FUS3 might function during embryogenic callus formation. However, at the shoot regeneration stage, BBM, L1L, ABI3, and FUS3 were down-regulated and Type-B ARRs were up-regulated, which might contribute to the increased shoot regeneration rate. CONCLUSIONS:A novel system for inducing shoot regeneration in tobacco has been developed using the GR-DEX system. Induced expression of AtLEC2 triggers embryogenic callus formation and overexpression of AtIPT7 or AtIPT9 improves shoot regeneration without exogenous cytokinin.
Project description:Glucocorticoids (GCs) are currently used for the therapeutic management of cholestatic diseases, but their use and molecular mechanism remain controversial. The aims of this study were 1) to assess the therapeutic effect of a 2-week treatment with the GC dexamethasone on hepatic damage in bile duct-ligated rats; 2) to investigate its effect on the activation of the nuclear receptors (NRs) pregnane X receptor (PXR), constitutive androstane receptor (CAR) and GC receptor (GR), and NF-kB, as well as on oxidative stress and bile acid (BA) hepatic composition. Cholestasis was induced by ligation of bile duct (BDL animals) in 16 male Wistar-Kyoto rats, and eight of them were daily treated by oral gavage with 0.125 mg/ml/kg DEX for 14 days. Eight Sham-operated rats were used as controls. Severity of cholestasis was assessed histologically and on plasma biochemical parameters. The nuclear expression of NF-kB (p65), GR, PXR and CAR was measured in hepatic tissue by Western Blot. Oxidative stress was evaluated by measuring malondialdehyde, carbonylated proteins, GHS and ROS content in rat livers. LC-MS was used to measure the plasma and liver concentration of 7 BAs. Histological findings and a significant drop in several markers of inflammation (p65 nuclear translocation, mRNA expressions of TNF-?, IL-1?, IL-6) showed that DEX treatment reversed cholestasis-induced inflammation, and similar results have been obtained with oxidative stress markers. The nuclear expression of p65 and CAR were inversely correlated, with the latter increasing significantly after DEX treatment (p<0.01 vs vehicle). Hepatic BA levels tended to drop in the untreated cholestatic rats, whereas they were similar to those of healthy rats in DEX-treated animals. Plasma BAs decreased significantly in DEX-treated animals with respect to untreated cholestatic rats. In conclusion, DEX reduces inflammation and oxidative stress in BDL rats, and probably CAR is responsible for this effect. Therefore, this NR represents a promising pharmacological target for managing cholestatic and inflammatory liver diseases.
Project description:Mutation of phytoglobin 2 (Pgb2) increases the number of somatic embryos in Arabidopsis. To assess the effects of the cellular localization of Pgb2 on embryo formation, an inducible system expressing a fusion protein consisting of Pgb2 linked to the steroid-binding domain of the rat glucocorticoid receptor (GR) was introduced in a pgb2 mutant line lacking the ability to express Pgb2. In this transgenic system, Pgb2 remains in the cytoplasm but migrates into the nucleus upon exposure to dexamethasone (DEX). Pgb2 retention in the cytoplasm, in the absence of DEX, increased the number of somatic embryos and reduced the expression of MYC2 - an inhibitor of the synthesis of auxin, which is the inductive signal for embryogenesis. Removal of DEX also induced the expression of several genes involved in the biosynthesis of tryptophan and the auxin, indole-3-acetic acid (IAA). These genes included: tryptophan synthase-? subunit (TSA1) and tryptophan synthase-? subunit (TSB1), which are involved in the synthesis of tryptophan, cytochrome P450 CYP79B2 (CYP79B2) and amidase 1 (AMI1), which participate in the formation of IAA via indole-3-acetaldoxime, and several members of the YUCCA family, including YUC1 and 4, which are also required for IAA synthesis. Retention of Pgb2 in the cytoplasm by removal of DEX increased the staining pattern of IAA along the cotyledons of the explants generating embryogenic tissue. Staining for IAA decreased when Pgb2 translocated into the nucleus in response to the application of DEX. Collectively, these results suggest that the presence of Pgb2 in the cytoplasm, but not in the nucleus, phenocopies the effects of Pgb2 mutation in inducing somatic embryogenesis.
Project description:In Arabidopsis thaliana, the phytohormone auxin is an important patterning agent during embryogenesis and post-embryonic development, exerting effects through transcriptional regulation. The main determinants of the transcriptional auxin response machinery are AUXIN RESPONSE FACTOR (ARF) transcription factors and AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) inhibitors. Although members of these two protein families are major developmental regulators, the transcriptional regulation of the genes encoding them has not been well explored. For example, apart from auxin-linked regulatory inputs, factors regulating the expression of the AUX/IAA BODENLOS (BDL)/IAA12 are not known. Here, it was shown that the HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP) transcription factor HOMEOBOX PROTEIN 5 (HB5) negatively regulates BDL expression, which may contribute to the spatial control of BDL expression. As such, HB5 and probably other class I HD-ZIP proteins, appear to modulate BDL-dependent auxin response.
Project description:Calcitriol, the active form of vitamin D, in combination with the glucocorticoid dexamethasone (Dex) has been shown to increase the antitumor effects of calcitriol in squamous cell carcinoma. In this study we found that pretreatment with Dex potentiates calcitriol effects by inhibiting cell growth and increasing vitamin D receptor (VDR) and VDR-mediated transcription. Treatment with actinomycin D inhibits Vdr mRNA synthesis, indicating that Dex regulates VDR expression at transcriptional level. Real time PCR shows that treatment with Dex increases Vdr transcripts in a time- and a dose-dependent manner, indicating that Dex directly regulates expression of Vdr. RU486, an inhibitor of glucocorticoids, inhibits Dex-induced Vdr expression. In addition, the silencing of glucocorticoid receptor (GR) abolishes the induction of Vdr by Dex, indicating that Dex increases Vdr transcripts in a GR-dependent manner. A fragment located 5.2 kb upstream of Vdr transcription start site containing two putative glucocorticoid response elements (GREs) was evaluated using a luciferase-based reporter assay. Treatment with 100 nm Dex induces transcription of luciferase driven by the fragment. Deletion of the GRE distal to transcription start site was sufficient to abolish Dex induction of luciferase. Also, chromatin immunoprecipitation reveals recruitment of GR to distal GRE with Dex treatment. We conclude that Dex increases VDR and vitamin D effects by increasing Vdr de novo transcription in a GR-dependent manner.
Project description:Brain-derived neurotrophic factor (BDNF) is involved in many functions such as neuronal growth, survival, synaptic plasticity and memorization. Altered expression levels are associated with many pathological situations such as depression, epilepsy, Alzheimer's, Huntington's and Parkinson's diseases. Glucocorticoid receptor (GR) is also crucial for neuron functions, via binding of glucocorticoid hormones (GCs). GR actions largely overlap those of BDNF. It has been proposed that GR could be a regulator of BDNF expression, however the molecular mechanisms involved have not been clearly defined yet. Herein, we analyzed the effect of a GC agonist dexamethasone (DEX) on BDNF expression in mouse neuronal primary cultures and in the newly characterized, mouse hippocampal BZ cell line established by targeted oncogenesis. Mouse Bdnf gene exhibits a complex genomic structure with 8 untranslated exons (I to VIII) splicing onto one common and unique coding exon IX. We found that DEX significantly downregulated total BDNF mRNA expression by around 30%. Expression of the highly expressed exon IV and VI containing transcripts was also reduced by DEX. The GR antagonist RU486 abolished this effect, which is consistent with specific GR-mediated action. Transient transfection assays allowed us to define a short 275 bp region within exon IV promoter responsible for GR-mediated Bdnf repression. Chromatin immunoprecipitation experiments demonstrated GR recruitment onto this fragment, through unidentified transcription factor tethering. Altogether, GR downregulates Bdnf expression through direct binding to Bdnf regulatory sequences. These findings bring new insights into the crosstalk between GR and BDNF signaling pathways both playing a major role in physiology and pathology of the central nervous system.
Project description:We sorted for GFP+ cells using the enhancer trap line J2632 with the UAS promoter driving the expression of an inducible (by dexamethasone - Dex) constitutive active version of the ARR1 gene (ARR1ΔDDK). We obtained the transcriptional profile of lateral root cap cells Overall design: Seedlings were grown for 5 days. Time-course expression profiling at 3 time points: J2632-UAS::ARR1ΔDDK-GR untreated (T0), 1 hour (T1) and 4 hour (T2) Dex-treated. J2632-UAS::ARR1ΔDDK-GR sorted fluorecent cells were harvested for RNA extraction.
Project description:Comparison of mp mutant seedlings with transgenics carrying a dexamethasone-inducible GR-bodenlos gene. Seedlings were pretreated with control medium or medium containing dexamethasone, followed by a 1 hour auxin treatment, and expression profiles were compared using Affymetrix ATH1 arrays.