Natural selection in action: molecular evolution of resistance to anti-microbials

BROWN_J20DTP

Evolution of resistance to drugs and pesticides is a problem of great practical importance and is also one of the clearest demonstrations of natural selection in action. In both medicine and agriculture, the emergence of resistant genotypes poses a serious challenge to control of infectious diseases. Knowledge about the mechanisms and evolution of resistance will inform the development of 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, and target two proteins in the sterol biosynthesis pathway, ERG24 and ERG2. Although some crop pathogens have moderate 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. It suggests that resistance to morpholines involves a fitness penalty and that stronger resistance incurs a higher cost. Morpholines may thus be particularly useful in multi-drug treatments for persistent infection.

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 function of these mutations will then be tested in yeast as a model organism, using a range of CRISPR/Cas9 protocols for site-directed mutagenesis and saturation mutation. The work will include assessment of the effects of mutations on fungicide resistance, the target protein and fungal fitness in yeast. The project will give a student outstanding training and research experience in molecular genetics, molecular evolution and plant pathology.