Supervisors: Professor Beverley Glover and Dr Samuel Brockington
A transcriptional complex comprising a WDR scaffold, one of a few bHLH proteins and one of a larger number of MYB proteins operates in Arabidopsis to regulate a variety of developmental programmes that together can loosely be thought of as specifying cellular identity. The flexibility of the module lies in the different combinations of MYB and bHLH proteins that can be attached to the WDR core. The MYB proteins can result in a transcriptional complex that is a positive regulator (eg of trichome development or anthocyanin synthesis) or a negative regulator (also of trichome development, or of root hair development).
It is not yet clear to what extent this transcriptional complex is similarly flexible in other angiosperms. The core components are known from maize and petunia, where they have been shown to work together, but we do not know whether flexibility of the MYB component creates the same range of cellular outcomes as is seen in Arabidopsis. Furthermore we do not know whether the complex, or indeed any of its components, exists at all outside the angiosperms, and to what extent they contribute to diverse cellular structures in early land plants.
This project will combine phylogenetic approaches to understanding gene family evolution with molecular genetic tests of gene function in diverse plant lineages. During the project you will tackle some or all of the following strands, as time and interest allow:
- Phylogenetic reconstruction of the WDR, bHLH and MYB protein subfamilies that contribute to the complex, to develop hypotheses about how early the complex might have evolved.
- In silico domain analysis of proteins involved in complex formation. We will explore whether the protein domains essential for complex formation in the 3 protein families are conserved across the phylogenies, and assess whether we can determine when this complex evolved. In vitro tests of protein-protein interaction might also be necessary in this strand of the project.
- Using the phylogenies produced in 1 we will explore whether diversity in complex function arose in particular plant groups by lineage-specific radiations in certain gene families.
- The hypotheses produced from the bioinformatics analyses above will be tested by selecting genes from key phylogenetic positions (eg the “oldest” MYB that has the interacting domains) and assessing the extent to which they can complement Arabidopsis mutants in the same component of the complex.
- You will also explore endogenous function of module members at key phylogenetic positions by expression analyses (such as quantitative RT-PCR and in situ hybridisation) and, where possible, transgenic knockout approaches in model species. This work will likely include experiments with moss, liverworts, and angiosperms.
- Ramsay, N. and Glover, B.J. 2005. The MYB/MYC/bHLH complex and the evolution of cellular diversity. Trends in Plant Science 10, 63-70.