CHARACTERIZATION OF THE RADISH MITOCHONDRIAL ORFB LOCUS - POSSIBLE RELATIONSHIP WITH MALE-STERILITY IN OGURA RADISH

The orfB locus of the normal (fertile) and Ogura (male-sterile) radish mitochondrial genomes has been characterized in order to determine if this region, which has previously been correlated with cytoplasmic ma le sterility (CMS) in Brassica napus cybrids (Bonhomme et al. 1991; Te mple et al. 1992), could also be involved in radish CMS. In normal rad ish, orfB is expressed as a 600-nucleotide (nt) transcript. In Ogura r adish, orfB is present as the second gene of a 1200-nt transcript that also contains a 138-codon open reading frame (orf138). Sequences show ing similarity to orf138 are present in normal radish, but are not exp ressed.