title: Organization of the mitochondrial Cob 2 pseudogene in different lines of rice.
abstract: In the fertile rice line IR 36 there are two copies of the apocytochrome b (cob) gene: a functional copy, cob 1, and a pseudogene, cob 2 (Kaleikau et al. 1992). In a survey of diverse rice lines, we found that cob 2 was absent in the wild abortive(WA)-type cytoplasmic male-sterile cytoplasm, but was present in the fertile lines. While cob 1 was conserved among all the lines, fertile and sterile, the cob 2 region was different in the fertile lines tested. The 5' regions of most cob 2 loci were similar to cob 1 (about 4 kb of the flanking region and most of the coding region), but the 3' region varied among different fertile lines. The point of divergence, the break-point, from the cob 1 sequence was conserved in all the cob 2 regions tested. In all the cob 2 regions, this break-point seems to be linked to the variable region of cob 2 through a conserved 192-bp segment, which is not a part of cob 1. It is proposed that the cob 2 regions could have been produced by recombination or insertion events involving cob 1 and the 192-bp segment which is present at different locations in the mitochondrial genomes of the various rice lines.
authors.affiliation: Centre for Biotechnology, SPIC Science Foundation, 110 Mount Road, 600 032, Madras, India.
authors.forename: K K
authors.initials: KK
authors.lastname: Narayanan
authors.forename: P
authors.initials: P
authors.lastname: Senthilkumar
authors.forename: V V
authors.initials: VV
authors.lastname: Sridhar
authors.forename: G
authors.initials: G
authors.lastname: Thomas
authors.forename: J
authors.initials: J
authors.lastname: Thomas