Identification of group-I introns at three different positions within the 28S rDNA gene of the entomopathogenic fungus Metarhizium anisopliae var. anisopliae

Using a set of heterologous primers designed from the 3'-end of the 28S rRN A gene of Verticillium dahliae the corresponding gene region of 30 isolates of the entomopathogenic fungus Metarhizium anisopliae var. anisopliae was amplified, The polymerase chain reaction products obtained could be classif ied into four groups varying in size from 1.0 to 2.2 kb, Sequence analyses of representative PCR products revealed the presence of five distinct intro ns, positioned in three different insertion sites, Fungal isolates 316 and 11 both harbored one intron each (374 and 337 bp in size, respectively), wh ereas isolate 33 harbored three introns (436, 334, and 412 bp) within the r elevant 28S rRNA region. All five introns shared the conserved P, Q, R, S e lements and all the other characteristic features of group-I introns in the ir deduced secondary structure; three (316-int, 33-int1, and 33-int3) belon g to subgroup IC1 and two (33-int2 and Ii-int) belong to subgroup IE. Furth er, reverse transcription polymerase chain reactions indicated that all the se introns were absent from the mature RNA molecules. The appearance of the five introns at identical positions with those from other organisms belong ing to various phyla is discussed, (C) 2001 Academic Press.