The mechanism of resistance to sterol 14α demethylation inhibitors in a mutant (Erg 40) of Ustilago maydis
✍ Scribed by Jenny A Butters; Ming C Zhou; Derek W Hollomon
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 183 KB
- Volume
- 56
- Category
- Article
- ISSN
- 1526-498X
No coin nor oath required. For personal study only.
✦ Synopsis
Resistance to DMI fungicides is a problem in both agriculture and medicine. Several mechanisms of resistance exist, but, as yet, few have been characterised in ®eld resistant strains of plant pathogens. One approach to evaluating the role of mutations in the sterol 14a demethylase (14DM) target site requires cloning this gene and con®rming its identity by complementation in an appropriate mutant. The azole-resistant mutant, Erg 40, of Ustilago maydis which is totally blocked at the 14a demethylation step in sterol biosynthesis seems to be suitable for such expression studies.
Transformation of Erg 40 with a plasmid containing the yeast 14a demethylase (CYP51A1) gene removed the block in sterol biosynthesis and generated azole-sensitive transformants. Detailed analysis of these transformants failed to detect the presence of the yeast gene and suggested, instead, that changes in sterol biosynthesis resulted simply from the transformation protocol and not from the incorporation of extracellular DNA. Subsequent sequence analysis has revealed a mutation in the 14a demethylase gene of Erg 40. The results suggest that azole resistance in Erg 40 is not simply controlled by this mutation but involves some additional regulatory function, and consequently Erg 40 is not suitable for complementation studies with CYP51A1 genes.