Microbial warfare in the phyllosphere

Plant pathogens pose major challenges to the production of crops and in the resilience of our trees and forests. How we protect plants from their most damaging pathogens is therefore vital to a future of sustainable agriculture within a healthy ecosystem. The Kettles laboratory combines molecular biology and protein biochemistry with computational approaches to study what makes bacterial and fungal phytopathogens so adept at causing disease. We also investigate how the immune systems of both crops and trees function to repel pathogens, and how this could be improved to enhance disease resistance. We have recently established a research program that focusses on diseases of oak trees. The two oak tree pathosystems we study are the bacterial complex associated with acute oak decline (AOD) disease and the oak powdery mildew fungus Erysiphe alphitoides.

The majority of plant tissues are colonised by complex communities of microorganisms (microbiomes) that perform functions critical to plant health. These functions include protection from biotic challenges, as disruption of a “healthy” microbiome can lead to the proliferation of opportunistic pathogens. The leaves and stems of plants are colonised by diverse groups of bacteria and fungi that together form the phyllosphere microbiome (Vorholt 2012).

For a microorganism to become a successful pathogen, it must parasitise a host to obtain nutrition, whilst simultaneously evading or suppressing the host immune system. Plant pathogens achieve this through the deployment of secreted effector proteins. The roles of effector proteins in disease development are diverse, and the function of many effectors in host manipulation have been previously described. Using both the AOD and oak powdery mildew pathosystems, this project aims to test the hypothesis that pathogen effectors have additional roles in antagonistic interactions within phyllosphere microbiomes (Snelders et al. 2018). This secondary role of effector proteins may offer a mechanistic explanation for how healthy microbiomes shift towards “pathobiomes” that are dominated by a single, or small group, of pathogenic organisms.
This project will allow the student to develop expertise in the areas of plant pathology, confocal fluorescence microscopy, RNAseq, protein biochemistry and bacterial/fungal mutagenesis. Applications are encouraged from graduates in the following disciplines: plant biology, microbiology, biochemistry and bioinformatics.

To discuss this project further, please contact Dr Graeme Kettles ([Email Address Removed]).