Foxy: an active family of short interspersed nuclear elements from Fusarium oxysporum

A novel family of short interspersed nuclear elements (SiNEs) has been iden tified in Fusarium oxysporum. This family has been called Foxy. The feature that makes Foxy unique among SINEs is the presence of 5' terminal tetranuc leotide repeats. Both the number and the sequence of these repeats vary bet ween individual members of the family. The genome of F. oxysporum f. sp. ly copersici contains at least 160 copies of Foxy. In a mutant obtained upon g amma irradiation of a wild-type isolate, 13 new Foxy insertions were identi fied. These observations, together with the occurrence of many Foxy-specifi c polymorphisms between isolates within one vegetative incompatibility grou p and the presence of Foxy-specific transcripts in the fungus, indicate tha t Foxy is currently active and may contribute to the genetic variability of F. oxysporum. Since we have not been able to detect Foxy sequences by PCR analyses in other fungi, this novel family of SINEs seems to be confined to Fusarium species.