Mode-of-Action and Spectrum of a Novel Fungicide Target

Project
The overall objective of this project will be to improve understanding and development of the novel fungicide target. This will be achieved through the following aims:
1. Corroborate mode of action (MoA) (12 months). The Nottingham group has discovered more than 20 new combinations of related agents which may work in a similar way, but translation fidelity has been tested as the relevant target only for some. To test this more broadly, the student will combine dual-reporter mistranslation assays (where expression of one out of two reporters requires a mistranslation event) with genetic and physiological tools (such as altering amino acid supply) [1] to key fungi of interest. The combinations of agents include certain metals and other currently-approved fungicides as well as a number of new agents. The MoA know-how gained by the student will inform identification and development of additional agents predicted to have the same target.

2. Novel combinations with similar MoA (12 months). Corroboration of the MoA (in Aim 1) will help the student to identify and test alternative, potentially more-effective, agents that can be used in the combinations. For example, different sulphate transport inhibitors are effective in the current combinations, possibly because these limit availability of certain (S-containing) amino acids needed for translation. The most effective of these would be used to screen chemical libraries available in Nottingham and at Syngenta, to find new combinations that produce synergistic growth inhibition. Reciprocally, the best agents arising from that screen can then be used to probe the libraries for agents more effective than the current best sulphate transport inhibitor. The screens will use the model yeast S. cerevisiae for convenience in high-throughput format, before testing novel lead combinations for efficacy against key phytopathogens. The studies to date have translated well from yeast to phytopathogens.

3. Phytopathogen range and selectivity (12 months). Tests so far have focused on three phytopathogens, against which different combinations appear to have different relative efficacies. The student will examine a much broader range of phyopathogens including isolates resistant to existing fungicides, to characterise phylogenetic relatedness or other feature (e.g., expressed sulphate transporters) that determines sensitivity to the novel fungicides. Findings-to-date also indicate specificity for fungi versus other organisms [1]. Accordingly, sulphate uptake is not involved in amino acid supply to humans so, unlike in fungi, sulphate transport inhibitors should not provoke mistranslation. Similarly, plants transport amino acid products from the roots to other parts, in preference to de novo synthesis dependent on sulphate. This project will help to corroborate that fungi express mechanisms required for the synergy to work which are absent in non-target organisms. This important analysis will give added breadth to the student's training, complementing the preceding phytopathogen-focused experiments.