IDENTIFICATION OF GROUP-I INTRONS IN THE 28S RDNA OF THE ENTOMOPATHOGENIC FUNGUS BEAUVERIA-BRONGNIARTII

The length of the 28s ribosomal DNA differs significantly between two strains (Bt102 and Bt114) of the entomopathogenic fungus Beauveria bro ngniartii. RFLP analysis on PCR products revealed the presence of thre e insertional elements of 350-450 bp in strain Bt114. One of the inser tions has been cloned and sequenced and shown to possess all the chara cteristic sequences and secondary structures of a group-IC intron. Its length is 428 bp and it is devoid of any long open reading frame. The distribution of this intron elsewhere in the genome of Bt114, as well as in the chromosomal ribosomal DNA, was studied. It seems to be pres ent as seven copies in different genes not corresponding to the mitoch ondrial DNA. The presence of the intron in other strains of B. brongni artii was examined by the hybridization method. Some of them seemed to possess introns with a similar core although others presented no homo logy with the cloned fragment.