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.
相似文献