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Impact of Recently Emerged Sterol 14 alpha-Demethylase (CYP51) Variants of Mycosphaerella graminicola on Azole Fungicide Sensitivity / H. J Cools; J. G. L Mullins; B. A Fraaije; J. E Parker; D. E Kelly; J. A Lucas; S. L Kelly; Jonathan Mullins; Steven Kelly; Diane Kelly; Josie Parker
Applied and Environmental Microbiology, Volume: 77, Issue: 11, Pages: 3830 - 3837
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<p><span>The progressive decline in the effectiveness of some azole fungicides in controlling</span><span>Mycosphaerella graminicola</span><span>, causal agent of the damaging </span><span>Septoria</span><span> leaf blotch...
|Published in:||Applied and Environmental Microbiology|
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<p><span>The progressive decline in the effectiveness of some azole fungicides in controlling</span><span>Mycosphaerella graminicola</span><span>, causal agent of the damaging </span><span>Septoria</span><span> leaf blotch disease of wheat, has been correlated with the selection and spread in the pathogen population of specific mutations in the </span><em>M. graminicola CYP51</em><span> (</span><em>MgCYP51</em><span>) gene encoding the azole target sterol 14α-demethylase. Recent studies have suggested that the emergence of novel MgCYP51 variants, often harboring substitution S524T, has contributed to a decrease in the efficacy of prothioconazole and epoxiconazole, the two currently most effective azole fungicides against </span><span>M. graminicola</span><span>. In this study, we establish which amino acid alterations in novel MgCYP51 variants have the greatest impact on azole sensitivity and protein function. We introduced individual and combinations of identified alterations by site-directed mutagenesis and functionally determined their impact on azole sensitivity by expression in a</span><span>Saccharomyces cerevisiae</span><span> mutant YUG37::</span><em>erg11</em><span> carrying a regulatable promoter controlling native </span><em>CYP51</em><span> expression. We demonstrate that substitution S524T confers decreased sensitivity to all azoles when introduced alone or in combination with Y461S. In addition, S524T restores the function in </span><span>S. cerevisiae</span><span> of MgCYP51 variants carrying the otherwise lethal alterations Y137F and V136A. Sensitivity tests of </span><span>S. cerevisiae</span><span> transformants expressing recently emerged MgCYP51 variants carrying combinations of alterations D134G, V136A, Y461S, and S524T reveal a substantial impact on sensitivity to the currently most widely used azoles, including epoxiconazole and prothioconazole. Finally, we exploit a recently developed model of the MgCYP51 protein to predict that the substantial structural changes caused by these novel combinations reduce azole interactions with critical residues in the binding cavity, thereby causing resistance.</span></p>
Swansea University Medical School