Effect of ERG6 Gene Extra Copies on Aspergillus fumigatus

Abstract:

To investigate the role of ERG6 gene in the growth rate and antifungal susceptibility,Aspergillus fumigatus strain with extra copies of ERG6 gene was constructed.Open reading frame (ORF) of putative ERG6 gene was searched in A.fumigatus genome.A PCR fragment, ERG6 ORF sandwiched by its flanking sequences (about 1 kb respectively),was amplified and was then subcloned into vector pRG-AMA1- NotI to produce a recombinant plasmid pERG6,which was further transformed into uracil auxotroph A.fumigatus strain AF293.1 to produce the transformant AF-empty as a control. Radial growth of the transformants was tested on minimal medium (MM) and YAG medi-um. Antifungal susceptibilities of these resulting transformants,AF-pERG6 and AF-empty. to the common antifungal agents were performed by using both disk diffusion and broth microdillution methods.A.fumigatus genome contains a ERG6 gene, of which the ORF size is 1 256 bp. Comparing to Candida albicans and Sacchromyces cerivisiae sterol methyltransferase,A. fumigatus Erg6p had 57% and 50% identity, and had 70% and 63% similarity in amino acid sequences,respectively. Radial growth of transformant AF-pERG6 was slower than that of transformant AF-empty. The antifungal susceptibilties of transformant AF-pERG6 to the antifungal drugs itraconazole,voriconazole,terbin-afine,amphotericin B, caspofungin and grisefolvin were same to that of transformant AF-empty. In A.fumigatus,extra copies of ERG6 gene have no effect on antifungal susceptibilities to itraconazole,voriconazole,terbinafine,amphotericin B, caspofungin and grisefolvin. Radial growth of A. fumigatus harboring extra copies of ERG6 gene becomes slower compared to the control.