Sequence and transcript analysis of the Nco2.5 Ogura-specific fragment correlated with cytoplasmic male sterility in Brassica cybrids

Abstract

Sequence analysis of the Ogura-specific mitochondrial DNA (mtDNA) fragment isolated previously from Brassica cybrids carrying Ogura cytoplasmic male sterility (cms) revealed a tRNA(fMet) sequence, a putative 138 amino acid open reading frame (orf138), and a 158 amino acid ORF (orf158) previously observed in mitochondrial genomes from several other plant species. Transcription mapping showed that both ORFs are present on a 1.4 kb cms-specific transcript. The orf158 sequence is also transcribed in fertile plants on a different mRNA, and thus is unlikely to be related to cms. On the other hand, fertile revertant plants lack transcripts of the orf138 sequence, whose possible role in the mechanism of Ogura cms is discussed.

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…Examination of fertile and sterile cybrids (containing the nuclear genome from Brassica but the radish cytoplasm) revealed an Ogura cytoplasm mtDNA region that was correlated with CMS composed of a unique transcribed gene termed orf138 next to the atp8 gene (Bonhomme et al, 1991(Bonhomme et al, , 1992. Unstable cybrids gave rise to fertile progeny in which the orf138 gene was lost or not transcribed (Bonhomme et al, 1992), providing strong evidence for its role in pollen abortion. The fertile revertant cybrids also lacked the 19-kD ORF138 protein detected in sterile lines (Grelon et al, 1994).…”

The Rf and Rf-like PPR in higher plants, a fast-evolving subclass of PPR genes

“…[13][14][15] These sister CMS are caused by the orf138 (Ogura) or the orf125 (Kosena) mitochondrial genes, which encode almost identical sterilityinducing proteins showing no homology with any other known proteins. [30][31][32] Both CMS originates from radish and were successfully transferred to rapeseed (Brassica napus) by protoplast fusion. Cloning of the associated restorer genes showed that Ogura and Kosena CMS Rf loci are identical and encode three highly similar PPR proteins out of which only one, PPR-B, carries the restoration activity.…”

Differentiation of the Cytoplasm of Japanese Cultivated Radishes (Raphanus sativus) into Four Types in the 3' Region of Mitochondrial Atp6

“…The variation of atp6 between the Ogura male-sterile and normal cytoplasms was first detected by Makaroff et al (1989). Though the causal association of the atp6 locus with the Ogura CMS was ruled out later (Bonhomme et al 1992), we found that the variation in the 5′ region completely coincided with the presence or absence of orf138 (Yamagishi and Terachi 1996). On the other hand, variations independent of the differentiation into normal and Ogura cytoplasms were observed in the orfB and coxI regions Terachi 2003).…”

“…Compared to the chloroplast genome, structural and sequence variations of the mitochondrial genome have been studied in detail in wild and cultivated radish (Raphanus) varieties. Studies on the mitochondrial genome have clarified the differences between the Ogura male-sterile and normal (fertile) cytoplasms (Bonhomme et al 1992), intra-and inter-specific sequence variations of the male-sterile gene, orf138, in the Ogura cytoplasm , and the differentiation in the normal type mitochondria Terachi 2003). The studies have also revealed the correspondence among the variations of mitochondrial genes.…”