PhD Studentship: Unpicking a Novel Plant Microbe Symbiosis: Bacteria as a Source of Odour in Carrion Flowers

University of Exeter - College of Life and Environmental Sciences

Main Supervisor: Dr Ben Raymond, College of Life Science         
Co-Supervisor: Dr Rob Griffiths, CEH Wallingford              
Co-Supervisor: Dr Katie Treseder &Dr Chris Bisson, Eden Project

The Titan Arum, Amorphophalus titanum, is an iconic example of carrion mimicry. At flowering a potent stench of rotting flesh is released in order to attract insect pollinators. The prevailing view of carrion mimicry is that plants produce volatile organic compounds themselves using flowers. However, a recent work in the Raymond lab has shown that bacteria, recovered from inflorescences, produce large quantities of the key fly-attracting volatiles released by many flowering Arums. These symbiotic bacteria are also efficient insect attractors in the absence of the plant. Thus, a previously undescribed plant-microbe symbiosis appears to be a key player in carrion mimicry, a major evolutionary novelty in pollination biology. This symbiosis could also explain many of the dramatic traits shown by the Titan Arum, such as gigantism and heat generation. However, the details of how this symbiosis is maintained, and how widespread it is among plants are entirely unknown.

There are two major aims of this PhD project. The first is to better characterize the transmission and dynamics of the microbial community in the Titan Arum, using the plants cultivated at Eden. Using metagenomics, qPCR and fluorescent microscopy we will monitor the dynamics of the microbial community during flowering and match these dynamics to the changing chemical composition of odours via mass spectrometry (in collaboration with Dr David Santillo, Greenpeace). We will also test for the presence and nature of vertical transmission of key microbes in fruits, via deep sequencing and culture-based methods.

The second aim will be to examine the prevalence of this bacterial symbiosis across diverse species of carrion flowers. We expect this association to be widespread and ancient in the Araceae, in particular. Bacteria will be sampled from botanical collections and from species in natural habitats such as the Dead horse Arum (Helicodiceros muscivorous) in the Mediterranean and also spotted Arum (Arum maculatum) and skunk cabagge (Lysichiton americanus) which are native and invasive in the UK, respectively. Key microbial taxa will be sequenced with both short and long read approaches in order to reconstruct phylogenies and examine evolutionary changes in the production of secondary metabolites.

Candidate: This project would suit someone with a background in microbiology, plant science or evolutionary biology who is interested in symbiosis, plant microbiomes or how interactions between plants and microbes shape key adaptations. The candidate should be keen to develop technical skills in molecular biology, sequencing, bioinformatics and mass spectrometry.

This PhD is supported by the Eden Project, who will contribute £2000 per annum to the running costs of the project as well as access to fruits and flowers of Titan Arum cultivated in their nurseries. Costs for a non-academic placement at Eden, focusing on outreach and education under their “Invisible Worlds” theme, will also be met by Eden.

Funding Maximum

3.5 year studentship: UK/EU/International tuition fees and an annual maintenance allowance at the Research Council rate of £14,553 per year.

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South West England