title: Mutations defective in ribonucleotide reductase activity interfere with pollen plastid DNA degradation mediated by DPD1 exonuclease.
abstract: Organellar DNAs in mitochondria and plastids are present in multiple copies and make up a substantial proportion of total cellular DNA despite their limited genetic capacity. We recently demonstrated that organellar DNA degradation occurs during pollen maturation, mediated by the Mg(2+) -dependent organelle exonuclease DPD1. To further understand organellar DNA degradation, we characterized a distinct mutant (dpd2). In contrast to the dpd1 mutant, which retains both plastid and mitochondrial DNAs, dpd2 showed specific accumulation of plastid DNAs. Multiple abnormalities in vegetative and reproductive tissues of dpd2 were also detected. DPD2 encodes the large subunit of ribonucleotide reductase, an enzyme that functions at the rate-limiting step of de novo nucleotide biosynthesis. We demonstrated that the defects in ribonucleotide reductase indirectly compromise the activity of DPD1 nuclease in plastids, thus supporting a different regulation of organellar DNA degradation in pollen. Several lines of evidence provided here reinforce our previous conclusion that the DPD1 exonuclease plays a central role in organellar DNA degradation, functioning in DNA salvage rather than maternal inheritance during pollen development.
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan.
authors.forename: Lay Yin
authors.initials: LY
authors.lastname: Tang
authors.forename: Ryo
authors.initials: R
authors.lastname: Matsushima
authors.forename: Wataru
authors.initials: W
authors.lastname: Sakamoto
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics* / Q000378:metabolism; D005095:Exoribonucleases / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D009154:Mutation; D010641:Phenotype; D030821:Plants, Genetically Modified; D018087:Plastids / Q000235:genetics; D011058:Pollen / Q000235:genetics / Q000648:ultrastructure; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012264:Ribonucleotide Reductases / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004272:DNA, Mitochondrial; D018744:DNA, Plant; D008164:Luminescent Proteins; D012264:Ribonucleotide Reductases; C561083:DPD1 protein, Arabidopsis; D005095:Exoribonucleases