title: The Mediator Complex MED15 Subunit Mediates Activation of Downstream Lipid-Related Genes by the WRINKLED1 Transcription Factor.
abstract: The Mediator complex is known to be a master coordinator of transcription by RNA polymerase II, and this complex is recruited by transcription factors (TFs) to target promoters for gene activation or repression. The plant-specific TF WRINKLED1 (WRI1) activates glycolysis-related and fatty acid biosynthetic genes during embryogenesis. However, no Mediator subunit has yet been identified that mediates WRI1 transcriptional activity. Promoter-β-glucuronidase fusion experiments showed that MEDIATOR15 (MED15) is expressed in the same cells in the embryo as WRI1. We found that the Arabidopsis (Arabidopsis thaliana) MED15 subunit of the Mediator complex interacts directly with WRI1 in the nucleus. Overexpression of MED15 or WRI1 increased transcript levels of WRI1 target genes involved in glycolysis and fatty acid biosynthesis; these genes were down-regulated in wild-type or WRI1-overexpressing plants by silencing of MED15 However, overexpression of MED15 in the wri1 mutant also increased transcript levels of WRI1 target genes, suggesting that MED15 also may act with other TFs to activate downstream lipid-related genes. Chromatin immunoprecipitation assays confirmed the association of MED15 with six WRI1 target gene promoters. Additionally, silencing of MED15 resulted in reduced fatty acid content in seedlings and mature seeds, whereas MED15 overexpression increased fatty acid content in both developmental stages. Similar results were found in wri1 mutant and WRI1 overexpression lines. Together, our results indicate that the WRI1/MED15 complex transcriptionally regulates glycolysis-related and fatty acid biosynthetic genes during embryogenesis.
authors.affiliation: Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 (M.J.K., I.-C.J.); andLaboratory of Plant Molecular Biology, Rockefeller University, New York, New York 10065 (N.-H.C.).
authors.forename: Mi Jung
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 (M.J.K., I.-C.J.); andLaboratory of Plant Molecular Biology, Rockefeller University, New York, New York 10065 (N.-H.C.).
authors.forename: In-Cheol
authors.identifier: 0000-0001-9408-4273
authors.initials: IC
authors.lastname: Jang
authors.affiliation: Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 (M.J.K., I.-C.J.); andLaboratory of Plant Molecular Biology, Rockefeller University, New York, New York 10065 (N.-H.C.) chua@mail.rockefeller.edu.
authors.forename: Nam-Hai
authors.identifier: 0000-0002-8991-0355
authors.initials: NH
authors.lastname: Chua
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D056892:Mediator Complex / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D012639:Seeds / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D005227:Fatty Acids; D047908:Intracellular Signaling Peptides and Proteins; D056892:Mediator Complex; C581741:NRB4 protein, Arabidopsis; D014157:Transcription Factors; C495665:WRINKLED1 protein, Arabidopsis