On the Evolution and Functional Significance of DNA Sequence Organization in Vascular Plants

Abstract

We have investigated properties of repeated DNA sequences in vascular plants for the purposes of assessing the way in which they may be useful to the organism and for probing the evolution of the nuclear genome. In pursuit of the first goal we have compared DNA sequence organization both in a diverse group of land plants and in a group of species within a single genus. We reasoned that if a particular arrangement of repeated sequences is important in basic metabolic events, such as the regulation of gene expression, then we might find a common pattern among closely related plants and perhaps among distantly related ones as well. Regardless of the role of repeated sequences in the genome, the processes by which the size of the genome has grown during the evolution of vascular plants is of intrinsic interest. Although little experimental evidence is currently available on the mechanisms for genome growth and rearrangement we suppose have occurred, we do have theory from which to work. The proposal that long blocks of tandemly repeating sequences (sometimes recognized as a satellite band in density gradients) could be periodically created and serve as precursor material for families of dispersed repeated sequences was first made by Britten and Kohne in 1968.