title: Loss of XRN4 function can trigger cosuppression in a sequence-dependent manner.
abstract: OLE1 encodes an oleosin isoprotein, a major membrane protein of the lipid-reserve organelle in seeds known as the oil body. Transgenic Arabidopsis were generated to contain an artificial chimeric transgene composed of OLE1 and green fluorescent protein (GFP). Overexpression of the fusion protein allowed visualization of the oil body size and structure in living cells using fluorescence microscopy. Two mutants, xrn4-8(OleG) and xrn4-9(OleG), accumulating enlarged oil bodies with reduced GFP fluorescence were isolated from the mutagenized progeny of a transgenic plant. Both mutants contained a defect in EXORIBONUCLEASE4 (XRN4), a gene known to encode a ribonuclease that specifically degrades uncapped mRNAs. Transgene expression was silenced in these mutants, as demonstrated by the reduced levels of the transgene mRNA and its product, OLE1-GFP. XRN4 loss of function also triggered cosuppression, i.e. simultaneous reduction in expression of the transgene and an endogenous OLE1 gene that shared a region of identical sequence. The enlarged oil bodies exhibiting reduced GFP fluorescence were formed in the xrn4-8(OleG) and xrn4-9(OleG) mutants due to the reduction of the endogenous OLE1 and the transgene product, OLE1-GFP, respectively. Cosuppression triggered by the xrn4 mutation also occurs for other genes such as PYK10, which encodes an endoplasmic reticulum (ER) body-resident β-glucosidase. The overall results indicate that a loss of XRN4 function can potentially trigger the cosuppression in a sequence-dependent manner.
authors.affiliation: Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan. makoto@nibb.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.forename: Chieko
authors.initials: C
authors.lastname: Nanba
authors.forename: Miyuki
authors.initials: M
authors.lastname: Saito
authors.forename: Maki
authors.initials: M
authors.lastname: Kondo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takeda
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Mikio
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D055314:Seed Storage Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D014170:Transformation, Genetic; D019076:Transgenes; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D055314:Seed Storage Proteins; C418137:Xrn1 protein, plant; C079353:oleosin protein, Arabidopsis; D049452:Green Fluorescent Proteins; D005095:Exoribonucleases; C473372:PYK10 protein, Arabidopsis; D001617:beta-Glucosidase