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

Abstract

A novel family of short interspersed nuclear elements (SINEs) has been identi®ed in Fusarium oxysporum. This family has been called Foxy. The feature that makes Foxy unique among SINEs is the presence of 5¢ terminal tetranucleotide repeats. Both the number and the sequence of these repeats vary between individual members of the family. The genome of F. oxysporum f. sp. lycopersici contains at least 160 copies of Foxy. In a mutant obtained upon gamma irradiation of a wild-type isolate, 13 new Foxy insertions were identi®ed. These observations, together with the occurrence of many Foxy-speci®c polymorphisms between isolates within one vegetative incompatibility group and the presence of Foxy-speci®c transcripts in the fungus, indicate that 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 con®ned to Fusarium species.

The biology and potential for genetic research of transposable elements in filamentous fungi

“…Among the retrotransposons of the SINE type already isolated (Table 1) the foxy element showed activity after gamma radiation treatment and subsequent new insertions (Mes et al, 2000).…”

“…immersus N. crassa Nectria haematococa Goyon et al, 1996Cambareri et al, 1998Shiflett et al, 2002 Kim et al, 1995Mes et al, 2000Kachroo et al, 1995Wei et al, 1996Rasmussen et al, 1993 pathogenic mutant were isolated and it was shown that by insertion of the impala element a pathogenicity gene could be cloned and sequenced (ORP1) which is essential for the penetration of M. grisea into the host leaf tissue. This gene did not present homology with known genes, showing the potential of transposable elements for cloning of pathogenicity genes.…”

“…Some of the factors that stimulate transposition have been tested on fungi, e.g. heat shock, copper sulfate and oxidative stress act on maggy retrotransposons in M. grisea ; gamma radiation increased the number of copies of the SINE element foxy in F. oxysporum (Mes et al, 2000); and exposure to chlorate activated rearrangement and induced skippy retrotransposon amplification in Fusarium (Anaya and Roncero, 1996).…”

Mobilization of a retrotransposon in 5-azacytidine-treated fungus Fusarium oxysporum

“…Ten transposons have been reported in Fusarium species (for review, see Wostemeyer and Kreibichl 2002), and one of them, Foxy (Mes et al 2000), was used in this experiment. Foxy is a short interspersed element (SINE) found in F. oxysporum f. sp.…”

“…Foxy in F. oxysporum strain F9 was cloned by polymerase chain reaction (PCR) under conventional conditions using total cell DNA and primers 5Ј-C T G G G T G G C T G TA AC G A AG C C -3 Ј a n d 5 Ј-GGAATTTTGAGAGAGTTCGCCT-3Ј. These primers were synthesized based on the terminal sequence of Foxy in the strain Fo1007 (Mes et al 2000). The cloned fragment consisted of 546 nucleotides and it contained two putative RNA polymerase binding sites (data not shown).…”