Genome organization in Fusarium oxysporum: clusters of class II transposons.

Several families of transposable elements (TEs) are present in the genome of the phytopathogenic fungus Fusarium oxysporum. They are present in copy numbers ranging from just a few elements to tens or hundreds per genome. Sequence analysis of contiguous stretches of genomic DNA surrounding insertion sites of one family revealed that they are packed with repeated sequences. We have carried out a detailed study of the composition and arrangement of these repeats in three chromosomal regions. We found that they are essentially mixtures of several types of TEs, most of them being DNA transposons, different from those previously characterized. Some repeats are frequently reiterated and many of them are inserted into other elements. Parts of these regions are also duplications. These regions appear prone to rearrangement and transposition and are subject to rapid reorganization.