Location: University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE
This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP). The GW4+ DTP consists of the Great Western Four alliance of the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus five Research Organisation partners: British Antarctic Survey, British Geological Survey, Centre for Ecology and Hydrology, the Natural History Museum and Plymouth Marine Laboratory. The partnership aims to provide a broad training in earth and environmental sciences, designed to train tomorrow’s leaders in earth and environmental science. For further details about the programme please see http://nercgw4plus.ac.uk/
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.
Project Aims and Methods:
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.
Training in wet lab molecular biology, evolutionary biology and computational statistics will be provided by BR and his group, with support from RG in sequencing and bioinformatics. The student may benefit from external training in phylogenetic reconstruction using bacterial whole genome data; courses on this topic are widely available from EMBO and the Wellcome Trust, among others. This project will also involve collaboration with the Greenpeace Research Laboratories (based in Exeter’s Streatham campus) who will train the candidate in sample preparation and analysis of mass-spectrometry data.
Shirasu, M., et al. (2010) Chemical identity of a rotting animal-like odor emitted from the inflorescence of the Titan Arum (Amorphophallus titanium). Biosci Biotechnol Biochem 74:2550-
Johnson, S.D. (2016) Carrion flowers. Current Biology 26: R543-
Stensmyr, M.C. et al (2002) Rotting smell of dead-horse arum florets. Nature 420:625
Schiestl, F.P. & Dotterl, S. (2012) The evolution of floral scent and olfactory preferences in pollinators. Evolution 66: 2042