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The MYB/bHLH/WDR complex and the evolution of cellular diversity in plants

Supervisor: Beverley Glover (Plant Sciences)

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Project outline:

The evolution of cellular diversity is one of the key factors that sets land plants apart from their algal ancestors, and this project will explore the evolution of the regulatory proteins that allowed new cellular diversity to arise. When plants conquered the land around 450 million years ago their transition into a dry environment with different materials (such as soil and air) and new challenges triggered the evolution of many new traits. We are particularly interested in the evolution of new types of differentiated cell, carrying out new functions in the plant. To understand how these new cell types evolved we must understand the developmental pathways that regulate them, and the evolution of the gene families that make up those developmental pathways.

A transcriptional complex comprising a WDR scaffold, one of a few bHLH proteins and one of a larger number of MYB proteins operates in model plants such as 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. It is not yet clear to what extent this transcriptional complex is similarly flexible in other angiosperms. More importantly, 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 plants.

  1. 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.
  2. 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. Tests of protein-protein interactions between potential partners will be carried out using yeast.
  3. We will test the hypotheses we generate by selecting genes from key phylogenetic positions (eg the "oldest" MYB that has the interacting domain) and assessing the extent to which they can complement Arabidopsis mutants in the same component of the complex.
  4. We will also explore endogenous function of module members at key phylogenetic positions by expression analyses (such as quantitative RT-PCR) and, where possible, transgenic knockout approaches in model species. This work will likely include experiments with moss, liverworts, and angiosperms.

Training:

The student will be given training in bioinformatics, light microscopy and scanning electron microscopy, in DNA/RNA extraction, sequencing, PCR, cloning, expression analysis (including quantitative RT-PCR), yeast-2-hybrid analysis and plant transformation. This is an exciting opportunity to learn a large range of molecular genetic techniques and their application to a range of different plant models.

Skills required:

The project is multidisciplinary, and will suit a student with a background in any of evolutionary biology, ecology or developmental biology who is willing to engage in an integrative approach. Some experience of molecular biology would be helpful. A demonstrated interest in plant evolution is important.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

  • 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.

Follow this link to find out about applying for this project.