NONRANDOM DISTRIBUTION OF TRANSPOSABLE ELEMENTS IN THE NUCLEAR GENOMEOF PLANTS

We have studied the genomic distribution of five different families of plant transposable elements by analyzing their location in DNA fracti ons from maize and tobacco genomes fractionated according to base comp osition. The results show that each family of elements is preferential ly integrated in one specific fraction of its respective host genome. This demonstrates that the distribution of transposable elements in th e nuclear genome of plants is not random but compartimentalized, i.e., the elements are located in specific genomic compartments characteriz ed by having a specific G+C content and representing a small proportio n of the genomes. Furthermore, these compartments seem to correspond t o the genomic regions where most of the plant genes are also located, suggesting a preferential integration of transposable elements in the transcriptionally active regions of the plant genome. The implications of these results on the current applications of transposon tagging te chniques are discussed.