Mechanisms and fitness penalties of fungicide resistance

BROWN_J21DTP

Evolution of resistance to drugs and pesticides is a serious challenge to control of infectious diseases in both agriculture and medicine. It is also one of the clearest demonstrations of natural selection in action. Knowledge about the mechanisms and evolution of resistance will inform the design of new anti-microbial compounds and new strategies for disease control.

In this project, the student will investigate the evolution of resistance to morpholine fungicides as a model for fitness costs of resistance. The morpholines are a small but important group of fungicides used in agriculture and medicine, which target two proteins in the sterol biosynthesis pathway, ERG24 and ERG2. Although some crop pathogens have become partially resistance to morpholines, there has been no known outbreak of complete resistance in commercial farming. This is a striking contrast to experience with other fungicides, suggesting that resistance to morpholines involves a significant fitness penalty. Morpholine chemistry may thus have potential for development of new fungicides with durable activity for controlling diseases of crops, people and other animals.

The student will test this hypothesis by studying the effect of mutations in ERG24 and ERG2 on responses to morpholines. This will first involve identifying sequence variation associated with morpholine resistance in crop pathogens. The ERG genes will be mutagenised in yeast as a model organism, using a range of CRISPR/Cas9 protocols for site-directed mutagenesis and saturation mutation. The effects of selected mutations on the biology and fitness of the fungus will then be investigated, including responses to fungicides, the structure of the ERG proteins, membrane sterol composition, and fungal growth and development. The project will give a student outstanding training and research experience in molecular genetics, molecular evolution and plant pathology.

References:

Fisher MC, Hawkins NJ, Sanglard D, Gurr SJ (2018) Worldwide emergence of resistance to antifungal drugs challenges human health and food security. Science 360: 739-742.

Arnold CJ, Chartrain L, Lawson D, Brown JKM: Role of sterol Δ14 reductase (ERG24) mutations in fungal resistance to morpholine and piperidine fungicides (to be submitted to a leading microbiology journal).

On a different group of sterol synthesis inhibitor fungicides (collaboration with North Carolina State University): Arnold CJ, Meyers EA, Chartrain L, Whetten R, Brown JKM, Cowger C: Effects of Cyp51 gene sequence, copy number and expression on evolution of resistance to triazole fungicides (to be submitted to Applied & Environmental Microbiology)