Unusual and Typical Features of a NovelRestorer-of-FertilityGene of Sugar Beet (Beta vulgarisL.)

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.

Inheritance and molecular mapping of Rf6 locus with pollen fertility restoration ability on A1 and A2 cytoplasms in sorghum

“…Several PPR genes acted as fertility restorers in commercially important CMS systems in a range of crop species [53] except for aldehyde dehydrogenase (Rf2) in maize [54], glycine-rich protein (Rf2) in rice [55], unknown protein (Rf17) in rice [56] and a yeast Oma1-like peptidase (Rf1) in sugar beet [57]. Rf locus tend to occur in clusters of PPR genes as observed in many species including rice [58], maize [59].…”

Targeted Sequence Capture Provides Insight into Genome Structure and Genetics of Male Sterility in a Gynodioecious Diploid Strawberry,Fragaria vescassp.bracteata(Rosaceae)

“…Some Rf loci belong to other protein families but still function by blocking the CMS locus ( e.g. , Matsuhira et al 2012). Only one copy of an Rf allele is generally necessary for CMS silencing (but see Schnable and Wise 1998; Kohls et al 2011), so fertility restoration is typically dominant and thus male sterility at Rf loci is typically recessive (Chase 2007).…”

Efficient callus formation and plant regeneration are heritable characters in sugar beet (Beta vulgaris L.)

“…These attributes enabled us to develop an Agrobacterium -mediated transformation system for sugar beet [3, 4]. Using this system, molecular analyses of several genes have been completed [5–7]. On the other hand, the shortcomings of NK-219mm-O include its vernalization requirement, i.e.…”