AN OVERVIEW OF EVOLUTION IN PLANT 5S-DNA

The DNA sequence properties of 5S DNA (5S RNA gene plus spacer) from a wide range of families of plants is reviewed with particular reference to the possibility of using the information for phylogenetic inference. Although the data-base is extremely limited, the available evidence suggests that within a subclass or tribe phylogenetic inference can be made, provided that a knowledge about the number of chromosomal locations of the gene loci (5S Dna loci) is available. The evidence suggests little, if any, exchange occurs between the 5S DNA units at different chromosomal loci and the available data favour a mechanism involving amplification/deletion processes for creating structural changes at the 5S Dna loci. Sequences originating from species in the families Rosaceae, Poaceae, and Brassicaceae tended to group together in cladistic analyses but with low confidence limits. Surprisingly little of the spacer region showed conservation of sequence that may relate to a function in the control of transcription by RNA polymerase III.