ABSTRACT: PFT1, the MED25 subunit of the plant Mediator complex, promotes flowering through CONSTANS dependent and independent mechanisms in Arabidopsis
Project description:PFT1, the MED25 subunit of the plant Mediator complex, promotes flowering through CONSTANS dependent and independent mechanisms in Arabidopsis
Project description:Two aspects of light are very important for plant development: the length of the light phase or photoperiod and the quality of incoming light. Photoperiod detection allows plants to anticipate the arrival of the next season, whereas light quality, mainly the red to far-red ratio (R:FR), is an early signal of competition by neighbouring plants. phyB represses flowering by antagonising CO at the transcriptional and post-translational levels. A low R:FR decreases active phyB and consequently increases active CO, which in turn activates the expression of FT, the plant florigen. Other phytochromes like phyD and phyE seem to have redundant roles with phyB. PFT1, the MED25 subunit of the plant Mediator complex, has been proposed to act in the light-quality pathway that regulates flowering time downstream of phyB. However, whether PFT1 signals through CO and its specific mechanism are unclear. Here we show that CO-dependent and -independent mechanisms operate downstream of phyB, phyD and phyE to promote flowering, and that PFT1 is equally able to promote flowering by modulating both CO-dependent and -independent pathways. Our data are consistent with the role of PFT1 as an activator of CO transcription, and also of FT transcription, in a CO-independent manner. Our transcriptome analysis is also consistent with CO and FT genes being the most important flowering targets of PFT1. Furthermore, comparison of the pft1 transcriptome with transcriptomes after fungal and herbivore attack strongly suggests that PFT1 acts as a hub, integrating a variety of interdependent environmental stimuli, including light quality and jasmonic acid-dependent defences. Two genotypes, WT (Columbia) and pft1-1 mutants. Three biological replicates for each condition (genotype X temperature combination). RNA prepared independently for each sample.
Project description:Two aspects of light are very important for plant development: the length of the light phase or photoperiod and the quality of incoming light. Photoperiod detection allows plants to anticipate the arrival of the next season, whereas light quality, mainly the red to far-red ratio (R:FR), is an early signal of competition by neighbouring plants. phyB represses flowering by antagonising CO at the transcriptional and post-translational levels. A low R:FR decreases active phyB and consequently increases active CO, which in turn activates the expression of FT, the plant florigen. Other phytochromes like phyD and phyE seem to have redundant roles with phyB. PFT1, the MED25 subunit of the plant Mediator complex, has been proposed to act in the light-quality pathway that regulates flowering time downstream of phyB. However, whether PFT1 signals through CO and its specific mechanism are unclear. Here we show that CO-dependent and -independent mechanisms operate downstream of phyB, phyD and phyE to promote flowering, and that PFT1 is equally able to promote flowering by modulating both CO-dependent and -independent pathways. Our data are consistent with the role of PFT1 as an activator of CO transcription, and also of FT transcription, in a CO-independent manner. Our transcriptome analysis is also consistent with CO and FT genes being the most important flowering targets of PFT1. Furthermore, comparison of the pft1 transcriptome with transcriptomes after fungal and herbivore attack strongly suggests that PFT1 acts as a hub, integrating a variety of interdependent environmental stimuli, including light quality and jasmonic acid-dependent defences.
Project description:The Mediator complex is an evolutionary conserved multiprotein complex that plays an essential role in initiating and regulating transcription. Its function is to act as a universal adaptor between RNA Polymerase II and DNA-bound transcription factors to translate regulatory information from activators and repressors to the transcriptional machinery. We have found that the PFT1 gene (which encodes the MED25 subunit of the Mediator complex) is required for the uncompromised expression of both salicylic acid- and jasmonate-dependent defense genes as well as resistance to the leaf-infecting fungal pathogens, Alternaria brassicicola and Botrytis cinerea in Arabidopsis. Surprisingly, we found that the pft1/med25 mutant showed increased resistance to the root infecting pathogen Fusarium oxysporum and that this resistance was independent of classical defense genes. In addition, the over-expression of PFT1 led to increased susceptibility to F. oxysporum. Therefore, to explore this phenomenon further, we wished to use whole genome transcript profiling to identify which genes may be playing a role in pft1/med25-mediated resistance to F. oxysporum. Experiment Overall Design: We grew both WT and pft1/med25 plants for four weeks in soil. After four weeks we treated the plants by root-dipping in either water or a F. oxysporum spore suspension before replanting them back into soil. There were four independent replicates of each treatment and each replicate contained 20 plants each. The treatments were WT (mock): pft1 (mock): WT (infected): pft1 (infected). Each replicate (16 in total) was harvested after 48 hours and the resulting RNA was used for hybridization to an Affymetrix ATH1 chip.
Project description:The Mediator complex is an evolutionary conserved multiprotein complex that plays an essential role in initiating and regulating transcription. Its function is to act as a universal adaptor between RNA Polymerase II and DNA-bound transcription factors to translate regulatory information from activators and repressors to the transcriptional machinery. We have found that the PFT1 gene (which encodes the MED25 subunit of the Mediator complex) is required for the uncompromised expression of both salicylic acid- and jasmonate-dependent defense genes as well as resistance to the leaf-infecting fungal pathogens, Alternaria brassicicola and Botrytis cinerea in Arabidopsis. Surprisingly, we found that the pft1/med25 mutant showed increased resistance to the root infecting pathogen Fusarium oxysporum and that this resistance was independent of classical defense genes. In addition, the over-expression of PFT1 led to increased susceptibility to F. oxysporum. Therefore, to explore this phenomenon further, we wished to use whole genome transcript profiling to identify which genes may be playing a role in pft1/med25-mediated resistance to F. oxysporum.
Project description:Determining the role of the Mediator subunit MED25/PFT1 in coordinating the expression of glucose responsive genes in Arabidopsis thaliana
Project description:Mediator is a multiprotein transcriptional co-regulator complex composed of four modules; Head, Middle, Tail, and Kinase. It conveys signals from promoter-bound transcriptional regulators to RNA polymerase II and thus plays an essential role in eukaryotic gene regulation. We describe subunit localization and activities of Mediator in Arabidopsis through metabolome and transcriptome analyses from a set of Mediator mutants. Functional metabolomic analysis based on the metabolite profiles of Mediator mutants using multivariate statistical analysis and heat-map visualization shows that different subunit mutants display distinct metabolite profiles, which cluster according to the reported localization of the corresponding subunits in yeast. Based on these results, we suggest localization of previously unassigned plant Mediator subunits to specific modules. We also describe novel roles for individual subunits in development, and demonstrate changes in gene expression patterns and specific metabolite levels in med18 and med25, which can explain their phenotypes. We find that med18 displays levels of phytoalexins normally found in wild type plants only after exposure to pathogens. Our results indicate that different Mediator subunits are involved in specific signaling pathways that control developmental processes and tolerance to pathogen infections.
Project description:Human respiratory syncytial virus (RSV) is the leading cause of severe acute lower respiratory tract infections in infants worldwide. Non-structural protein NS1 of RSV modulates the host innate immune response by acting as an antagonist of type I and type III interferon (IFN) production and signaling in multiple ways. It is likely that NS1 performs this function by interacting with different host proteins. In order to obtain a comprehensive overview of NS1 interaction partners, we performed three complementary protein-protein interaction screens i.e. BioID, MAPPIT and KISS. The BioID proximity screen was performed during an RSV infection in A549 cells. MED25, a subunit of the Mediator complex, was identified in all 3 performed screening methods as a potential NS1 interacting protein. We confirmed the interaction between MED25 and RSV NS1 by co-immunoprecipitation, not only upon overexpression of NS1, but also with endogenous NS1 during RSV infection. We also demonstrate that the replication of RSV is enhanced in MED25 knockout A549 cells, suggesting a potential antiviral role of MED25 during RSV infection. Mediator subunits function as transcriptional coactivators and are involved in transcriptional regulation of their target genes. Therefore, the interaction between RSV NS1 and cellular MED25 might be beneficial during an RSV infection as this can affect host transcription and the host immune response to infection.
Project description:Our in vitro binding studies support a model whereby MED25 exhibits multivalent interactions with a subset of related ETS factors, ETV1/4/5. We hypothesize that the interaction would allow for coregulation of genes by ETV1/4/5 and MED25, acting perhaps to link the ETVs to the Mediator complex. To explore this possibility, we compared the genome occupancy for FLAG-tagged MED25 and ETV4 in the prostate cancer cell line PC3, which overexpresses ETV4. We also tested for relevance of MED25 and ETV4 binding to for gene expression in PC3s. We found a high degree of overlap in the FLAG-MED25 and ETV4 ChIPs datasets consistent with our model, and also identified a subset of target genes co-dependent on Med25 and ETV4.
Project description:Our in vitro binding studies support a model whereby MED25 exhibits multivalent interactions with a subset of related ETS factors, ETV1/4/5. We hypothesize that the interaction would allow for coregulation of genes by ETV1/4/5 and MED25, acting perhaps to link the ETVs to the Mediator complex. To explore this possibility, we compared the genome occupancy for FLAG-tagged MED25 and ETV4 in the prostate cancer cell line PC3, which overexpresses ETV4. We also tested for relevance of MED25 and ETV4 binding to for gene expression in PC3s. We found a high degree of overlap in the FLAG-MED25 and ETV4 ChIPs datasets consistent with our model, and also identified a subset of target genes co-dependent on Med25 and ETV4.