Turku Centre for Biotechnology
Supervisor: Stephen Rudd
Lichens are living organisms that are traditionally described as being formed through a symbiotic relationship between a fungal species and photosynthetic algal or cyanobacterial species. While the relationship between the hosts has widely been reported as a mutualistic relationship in which both species benefit, this has recently been questioned experimentally and the relationship may be interpreted correctly as a "controlled parasitism" with the photosynthetic species representing the victim. While molecular biological and genetic resources have been established for the systematic study and classification of lichen, no molecular evidence has yet been obtained that can dissect the physiological nature of the lichen relationships.
Existing molecular resources for lichen species are heavily biased towards the needs of taxonomic systematists and to the needs of evolutionary researchers. Lichens have not yet been investigated within a genomics context and there is currently no indication of any efforts to sample pairs of genomes that participate within lichen symbioses.
This project aims to establish a functional genomics platform for the lichen Cladonia rangiferina. It involves the construction of, and directed sequencing from, normalised cDNA libraries representing the cultured fungal (Cladonia rangiferina) and the algal (Trebouxia sp.) genomes and the mixed species lichen material under control and stress conditions. The construction of normalised cDNA libraries from various cultured, lichenised, stressed and anhydrobiotic tissues will aim to sample as broad a range of expressed algal and fungal genes as is possible. The EST sequences will be used to design an oligonucleotide microarray that may be used to analyse gene expression in cultured species and in the lichen. Both microarray based and proteomics approaches will be used to investigate the molecular mechanisms behind anhydrobiosis and to determine the functional contributions from both species to define whether the symbiosis is indeed mutualistic or if as presumed it is in fact merely controlled parasitism. A proteomics approach will be undertaken to further identify visible differences in the proteome within the same stages. Bioinformatics methods will be used to integrate the data and to identify meaningful patterns within the data. These data will be compared and contrasted with contemporary and computational biological knowledge from plant and fungal systems.
This project may be summarised as a development project where we intend to convert a dominant Finnish lichen species into a model system for the functional dissection of the molecular adaptations that allow the formation of the lichen, and in turn provide the lichen symbiont with the resources to survive in otherwise inhospitable environments.