THE TRANSPOSABLE ELEMENT IMPALA, A FUNGAL MEMBER OF THE TC1-MARINER SUPERFAMILY

A new transposable element has been isolated from an unstable niaD mut ant of the fungus Fusarium oxysporum. This element, called impala, is 1280 nucleotides long and has inverted repeats of 27 bp. Impala insert s into a TA site and leaves behind a ''footprint'' when it excises. Th e inserted element, impala-160, is cis-active, but is probably trans-d efective owing to several stop codons and frameshifts. Similarities ex ist between the inverted repeats of impala and those of transposons be longing to the widely dispersed mariner and Tc1 families. Moreover, tr anslation of the open reading frame revealed three regions showing hig h similarities with Tc1 from Caenorhabditis elegans and with the marin er element of Drosophila mauritiana. The overall comparison shows that impala occupies an intermediate position between the mariner and Tc1- like elements, suggesting that all these elements belong to the same s uperfamily. The degree of relatedness observed between these elements, described in different kingdoms, raises the question of their origin and evolution.