Abstract
In rice one particular CMS has been obtained by combining the cytoplasm of Chinsurah Boro II (indica rice) with the nuclear genome of Taichung 65 (japonica rice). The possibility has been reported that a unique sequence (orf79) located downstream from mitochondrial atp6 causes male sterility. In CMS lines, the B-atp6 transcript is a 2.0 kb RNA consisting of normal atp6 and a unique sequence containing orf79, whereas two discontinuous RNAs of 1.5 and 0.45 kb are generated from the 2.0 kb RNA by processing in presence of the Rf1. By means of map-based cloning and complementation test, we demonstrated that one of the PPR gene (PPR8-1) promotes the processing of B-atp6 RNA and restores pollen fertility. Sequence analysis around the Rf1 locus revealed there are two other PPR genes that have highly homology to the Rf1 gene. We are now analyzing the post-transcriptional regulation of B-atp6 RNA by the Rf1.
