RNA EDITING IN THE COX3 MESSENGER-RNA OF MAGNOLIA IS MORE EXTENSIVE THAN IN OTHER DICOT OR MONOCOT PLANTS

The Magnoliaceae are discussed as one of the key species at the root o f the flowering plants. To obtain molecular information for one of the se phylogenetically interesting plant species, we determined genomic a nd cDNA sequences of the mitochondrial cox3 gene in Magnolia grandiflo ra. Twenty-two RNA editing events are identified to alter cytidines in the mRNA to uridines, all but one of which change the encoded amino a cid identity, RNA editing in the cox3 coding region is thus more frequ ent in Magnolia than in other dicot or monocot plants investigated and almost as predominant as in some gpmnosperms. The cox3 RNA editing fr equency in Magnolia thus occupies an intermediate position between ang iosperms and gymnosperms consistent with the phylogenetic position of the Magnoliales.