Defence priming acts as a plant’s adaptive immune system – it increases sensitivity following prior experience to allow a faster and stronger response upon subsequent infection. For my project at the University of Birmingham, my supervisor, Dr Rosa Sanchez-Lucas, and I looked at defence priming in a relatively understudied species – oak. Previous studies demonstrated that salicylic acid (SA) or β-aminobutyric acid (BABA) can activate defence priming in oak, leading to enhance resistance to the fungal pathogen behind oak powdery mildew (Erysiphe alphitoides). This enhanced resistance is thought to occur due to increased SA-dependent gene expression and callose deposition at the site of infection. However, the exact mechanisms behind defence priming in oak, particularly the downstream signalling pathways and metabolites, remain unknown, and so their characterisation was the focus of my project.
The project began by exposing oak seedlings to jasmonic acid (JA), SA, BABA, or water prior to infection with E. alphitoides. Following these treatments, my main role was to assist with an untargeted metabolomic analysis of the seedlings in the hope of identifying metabolites putatively involved in defence priming in oak. I was provided with raw data for this, produced using LC-MS at 0, 1, and 2 dpi. I then processed this data using R to make analysis possible. Once I had processed the data, I uploaded it to Metaboanalyst, a free online software for analysing metabolomics data. Using Metaboanalyst I conducted a series of statistical analyses including, ANOVA, PCA, and PLS-DA. Based on this it appears that defence priming occurs within one day of infection and involves a whole range of metabolites. This is only the start of the analysis, and the hope is that further research will allow the identification and characterisation of specific metabolites, and their associated pathways, involved in defence priming.
Furthermore, to complement the metabolomics data analysis I conducted some microscopic and transcriptional analysis. For the microscopic analysis, I assessed the extent of fungal growth and subsequent callose deposition. For the transcriptional analysis, I assessed changes in expression of genes known to be involved in defence responses in other species. This complemented my remote analysis with wet lab experience, and I became confident with a number of techniques including florescence microscopy and qPCR.
One possible implication of this research is increased understanding of resistance mechanisms, which could be applied to protecting oak seedlings from oak powdery mildew, which may otherwise impair oak woodland restoration efforts. Moreover, on a personal level I have gained several skills that may be relevant to future careers. For example, transferable computational skills, the ability to effectively contribute as part of a team, and a willingness to adapt when things don’t go as planned.
Overall, I am grateful to the BSPP for funding this opportunity to further my knowledge and apply what I have learnt in lectures to real scientific research. This project has sparked a keen interest in plant pathology and inspired me to pursue a PhD and ultimately a career researching in this or other areas of the plant sciences.
University of Birmingham