title: Unusual and typical features of a novel restorer-of-fertility gene of sugar beet (Beta vulgaris L.).
abstract: Male gametogenesis in plants can be impaired by an incompatibility between nuclear and mitochondrial genomes, termed cytoplasmic male sterility (CMS). A sterilizing factor resides in mitochondria, whereas a nuclear factor, Restorer-of-fertility (Rf), restores male fertility. Although a majority of plant Rf genes are thought to encode a family of RNA-binding proteins called pentatrico-peptide repeat (PPR) proteins, we isolated a novel type of Rf from sugar beet. Two BACs and one cosmid clone that constituted a 383-kbp contig covering the sugar beet Rf1 locus were sequenced. Of 41 genes borne by the contig, quadruplicated genes were found to be associated with specific transcripts in Rf1 flower buds. The quadruplicated genes encoded a protein resembling OMA1, a protein known from yeast and mammals to be involved in mitochondrial protein quality control. Construction of transgenic plants revealed that one of the four genes (bvORF20) was capable of restoring partial pollen fertility to CMS sugar beet; the level of restoration was comparable to that evaluated by a crossing experiment. However, the other genes lacked such a capability. A GFP-fusion experiment showed that bvORF20 encoded a mitochondrial protein. The corresponding gene was cloned from rf1rf1 sugar beet and sequenced, and a solitary gene that was similar but not identical to bvORF20 was found. Genetic features exhibited by sugar beet Rf1, such as gene clustering and copy-number variation between Rf1 and rf, were reminiscent of PPR-type Rf, suggesting that a common evolutionary mechanism(s) operates on plant Rfs irrespective of the translation product.
authors.affiliation: Laboratory of Genetic Engineering, Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsuhira
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Kagami
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kurata
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kitazaki
authors.forename: Muneyuki
authors.initials: M
authors.lastname: Matsunaga
authors.forename: Yuko
authors.initials: Y
authors.lastname: Hamaguchi
authors.forename: Eiki
authors.initials: E
authors.lastname: Hagihara
authors.forename: Minoru
authors.initials: M
authors.lastname: Ueda
authors.forename: Michiyo
authors.initials: M
authors.lastname: Harada
authors.forename: Aki
authors.initials: A
authors.lastname: Muramatsu
authors.forename: Rika
authors.initials: R
authors.lastname: Yui-Kurino
authors.forename: Kazunori
authors.initials: K
authors.lastname: Taguchi
authors.forename: Hideto
authors.initials: H
authors.lastname: Tamagake
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Mikami
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Kubo
mesh_terms: D027461:Beta vulgaris / Q000235:genetics / Q000502:physiology*; D022202:Chromosomes, Artificial, Bacterial; D032461:Chromosomes, Plant; D003001:Cloning, Molecular; D005298:Fertility / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D045726:Metalloproteases / Q000235:genetics; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
chemical_list: D010940:Plant Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D045726:Metalloproteases; C480741:Oma1 protein, S cerevisiae