Project highlights

  • Investigate the factors driving specificity in ecologically-relevant symbioses. 
  • This study will use an integrative approach, combining experimental, modelling, and genomic methodologies. You will have the opportunity to learn new approaches and apply cutting-edge technologies in your research. 
  • You will gain mechanistic insights into cnidarian-algal symbioses that can be used to improve human interventions into the coral reef crisis. 

Overview

Mass coral bleaching events associated with thermal stress have caused substantial declines in coral ecosystems. Coral bleaching results from the breakdown in the relationship between the coral and its symbiotic algae of the family Symbiodiniaceae and can occur at temperatures just 1-2°C above the average summer maxima (Goreau et al., 2000). Nevertheless, it has been shown that changing the dominant association to a thermally tolerant symbiont can increase the coral holobiont’s bleaching threshold by up to 1.5°C (Berkelmans & Van Oppen, 2006). As such, it has been proposed that switching symbiotic partners may represent a viable mechanism for these thermally sensitive organisms to keep pace with future increases in sea surface temperatures (Baker et al. 2004; Buerger et al. 2020). 

Recent improvements in our approaches to analysing symbiont communities using the ITS2 marker are revealing a greater degree of host-symbiont specificity than was previously realised (Smith et al. 2017; Hume et al. 2019). Potential co- evolution and local adaptation in specific host-symbiont associations would likely act as a barrier to the acquisition of novel thermally resistant symbionts and suggests that the thermal tolerance of a particular symbiont may not be transferable to a new host. Despite the fundamental importance of specificity in these associations, the mechanisms underpinning specificity remain unresolved. In this project, you will combine experimental, genomic, field, and modelling approaches to investigate host-symbiont specificity in the cnidarian-algal symbiosis model system Exaiptasia diaphana. The project outcomes will provide valuable new insights into how genotype, environment, and developmental stage influence specificity in the symbiosis, with implications across host-symbiont systems and for organismal resilience to climate change.  

Three images of anemones showing different symbiotic states that can be maintained in the lab.

Figure 1: Exaiptasia diaphana as a model system for studying cnidarian-algal symbioses. These anemones can be maintained in the lab in both aposymbiotic (left) and symbiotic (middle) states. The capacity to maintain them in the aposymbiotic state enables experimental inoculations with different symbiotic partners. Further, establishment of the symbiosis can be easily monitored using fluorescence imaging (right). Image modified from Baumgarten et al. 2015, PNAS. 

Host

University of Warwick

Theme

  • Organisms and Ecosystems

Supervisors

Project investigator

Co-investigators

How to apply

Methodology

Using the cnidarian-algal symbiosis model E. diaphana, you will likely perform field sampling, symbiont infection assays, modelling of infection dynamics, experimental crosses between genotypes, and genomics/transcriptomics to elucidate the genetic, environmental, and developmental controls on host-symbiont specificity. 

Training and skills

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.  

Training will be provided in a range of different techniques, as required, including molecular biology (e.g., DNA/RNA extractions, PCR, sequencing library preparation for amplicon and whole genome sequencing), bioinformatics (e.g., population genomics, transcriptomics, microbial community analyses), and experimental assays (e.g., experimental design, symbiont infection assays, fluorescence microscopy).  

Further details

To learn more about the project, contact Ed Smith ([email protected]). Please include a CV, details of past research, and outline your interest in the project. 

Please see the lab page here. 

To apply to this project:  

  • You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.  

 Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025.  

Possible timeline

Year 1

Analysis of symbiont communities in field populations of E. diaphana. 

Year 2

Experimental infection assays and modelling of infection dynamics.

Year 3

Identification of genes and pathways modulating specificity in cnidarian-algal associations. 

Further reading

Buerger, P., Alvarez-Roa, C., Coppin, C.W., Pearce, S.L., Chakravarti, L.J., Oakeshott, J.G., Edwards, O.R. and Van Oppen, M.J.H., 2020. Heat-evolved microalgal symbionts increase coral bleaching tolerance. Science Advances, 6(20), p.eaba2498. 

Herrera, M., Klein, S.G., Campana, S., Chen, J.E., Prasanna, A., Duarte, C.M. and Aranda, M., 2021. Temperature transcends partner specificity in the symbiosis establishment of a cnidarian. The ISME journal, 15(1), pp.141-153. 

Smith, E.G., Ketchum, R.N. and Burt, J.A., 2017. Host specificity of Symbiodinium variants revealed by an ITS2 metahaplotype approach. The ISME Journal, 11(6), pp.1500-1503. 

Tortorelli, G., Belderok, R., Davy, S.K., McFadden, G.I. and Van Oppen, M.J., 2020. Host genotypic effect on algal symbiosis establishment in the coral model, the anemone Exaiptasia diaphana, from the Great Barrier Reef. Frontiers in Marine Science, 6, p.833. 

Thornhill, D.J., Xiang, Y., Pettay, D.T., Zhong, M. and Santos, S.R., 2013. Population genetic data of a model symbiotic cnidarian system reveal remarkable symbiotic specificity and vectored introductions across ocean basins. Molecular ecology, 22(17), pp.4499-4515.