Restorer genes for different forms of Brassica cytoplasmic male sterility map to a single nuclear locus that modifies transcripts of several mitochondrial genes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 17; pp. 10032 - 10037
• Main Authors: Li, X.Q. (McGill University, Montreal, Quebec, Canada.), Jean, M, Landry, B.S, Brown, G.G
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 18.08.1998; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: ALLELES; ALLELISM; ARN MENSAJERO; ARN MESSAGER; Biological Sciences; Botany; BRASSICA; BRASSICA NAPUS; CARTE GENETIQUE; CHROMOSOME MAPS; Cytoplasm; CYTOPLASMIC MALE STERILITY; ESTERILIDAD MASCULINA CITOPLASMICA; FERTILIDAD; FERTILITE; FERTILITY; Flowers & plants; GENE; GENES; Genetic loci; GENETIC MAPPING; GENETIC MAPS; GENETIC MARKERS; GENOMAS; GENOME; GENOMES; Genotypes; LINKAGE GROUPS; LOCI; LOCUS; MACHO; MALE; Male fertility; MALES; MAPAS GENETICOS; MARCADORES GENETICOS; MARQUEUR GENETIQUE; MESSENGER RNA; MITOCHONDRIA; Mitochondrial DNA; Mitochondrial genes; MITOCHONDRIE; MITOCONDRIA; MNT GENE; NUCLEAR GENOME; Plants; RFLP; RFN GENE; SINAPIS; SINAPIS ARVENSIS; STERILITE MALE CYTOPLASMIQUE
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.17.10032

The oilseed rape plant, Brassica napus, possesses two endogenous male sterile cytoplasms, nap and pol. Previous studies have shown that nuclear restoration of pol cytoplasmic male sterility (CMS) is conditioned by a gene, Rfp, that is also involved in modifying transcripts of the pol CMS-associated orf224/atp6 mtDNA region. We now find that the nap nuclear restorer gene Rfn apparently is identical to Mmt, a gene that conditions the modification of transcripts from several different mtDNA regions, including one that is associated with nap CMS and contains orf222, a chimeric gene related to orf224. Mmt, in turn, is found to be allelic to Rfp, suggesting that restorer genes for the two cytoplasm represent different alleles or haplotypes of a single nuclear locus. This view is supported by restriction fragment length polymorphism mapping studies that indicate that Rfn and Rfp map to the same chromosomal position. Thus, in contrast to CMS in other species, different forms of Brassica CMS are restored by alleles of a single nuclear locus, and the restoration properties of these alleles reflect their involvement in the modification of transcripts of corresponding CMS-associated mtDNA regions. A survey of 51 varieties from 8 Brassica and Sinapis species failed to find evidence of Rfn(Mmt) in other than fertility-restored, nap cytoplasm B. napus. This suggests that Rfn(Mmt) arose in Brassica with nap cytoplasm and that the necessity for fertility restoration may have provided the selective pressure for its origin and maintenance