Nuclear genes from Tx CMS maintainer lines are unable to maintain atp6 RNAediting in any anther cell-type in the Sorghum bicolor A3 cytoplasm

RNA editing and cytoplasmic male sterility are two important phenomena asso ciated with higher plant mitochondria. We recently have shown a potential f unction of RNA editing in CMS development. The frequency of atp6 RNA editin g was specifically reduced in anthers of male-sterile Sorghum bicolor, whic h increased in frequency in partially restored progeny. Here we present dat a that show that the loss of RNA editing capability also occurs in a second nuclear background that allows the expression of male sterility. Loss of R NA editing thus appears to be associated with unique combinations of male-s terile cytoplasm and non-restoring nuclear backgrounds. In addition, the re duction of RNA editing affects both gametophytic and sporophytic anther cel l-types but not other floral tissues. An analysis of F-2 plants exhibiting different levels of fertility indicates a co-segregation of fertility resto ration and atp6 RNA editing. The atp6 transcript abundance is similar in se edlings and anthers of male-sterile, partially restored, and male-fertile l ines and thus is not associated with loss of atp6 RNA editing in anthers. A model for RNA editing and male sterility based on the data available is pr esented. Functional correlations with other CMS systems are also discussed.