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Spurring evolution: understanding the development and diversity of nectar spurs

Supervisor: Beverley Glover (Plant Sciences)

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Project outline:

The enormous species diversity of the angiosperms was described by Darwin as “an abominable mystery”. Part of the explanation lies with the ways in which different plant species are reproductively isolated from one another, as a result of divergence of floral morphology and consequent differences in their interactions with pollinating animals. Nectar spurs are outgrowths of the flower, usually of a petal, that either produce nectar or hold nectar that is secreted elsewhere. Only a pollinating insect with a proboscis as long as the spur can access the nectar contained in it. Long-spurred flowers are therefore pollinated by different insects than short spurred flowers. Separation of plants within a family into reproductively isolated groups with different spur lengths and different pollinators results in rapid speciation. Therefore understanding spur evolution and development is central to understanding angiosperm radiation.

This project aims to understand the evolution and development of nectar spurs, because they drive reproductive isolation and speciation. Because no conventional molecular genetic model plant species produces nectar spurs, we know very little about their development and nothing about the molecular genetic control of that development. You will explore this developmental genetic problem in the genus Linaria, which has species with a very wide range of nectar spur lengths. This range of spur lengths allows us to take a comparative and evolutionary approach, and the ease with which the different species hybridise allows us to use genetic approaches to understand the developmental pathways.

This project will combine molecular genetic approaches to understanding nectar spur development with comparative morphological, microscopic and molecular genetic approaches to analyse spur length evolution. During the project you will tackle the following strands:

  1. Analyse the segregation of nectar spur length in the population of plants we have produced by crossing a long spurred species with a short spurred species of Linaria.
  2. Use bulk segregant analysis and next generation sequencing approaches to identify the genes controlling nectar spur development.
  3. You will explore the detailed function of the genes you identify by expression analyses (such as quantitative RT-PCR) and transgenic approaches in heterologous hosts.
  4. You will compare development of closely related Linaria species with different spur lengths, assessing how expression profiles of your key genes are associated with differences in nectar spur length and the number and size of cells in the spur.
  5. Use a modelling approach to explore how the genes involved in nectar spur development act together to produce the final shape and size of nectar spur.

Training:

The student will be given training in light microscopy and scanning electron microscopy, in genetic analysis of trait development, in phylogeny reconstruction and character mapping, DNA/RNA extraction, Illumina sequencing, PCR, cloning, expression analysis (including quantitative RT-PCR) and plant transformation. This is an exciting opportunity to learn a large range of molecular genetic and morphological techniques, including analysis of genomic data sets.

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. A demonstrated interest in plants would be helpful.

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:

  • Cullen, E., Fernandez-Mazuecos, M. & Glover, B.J. (2018) Evolution of nectar spur length in a clade of Linaria reflects changes in cell division rather than in cell expansion. Annals of Botany mcx213, https://doi.org/10.1093/aob/mcx213
  • Fernandez-Mazuecos, M. & Glover, B.J. (2017) The evo-devo of plant speciation. Nature Ecology and Evolution 1, 0110.
  • Box, M.S., Dodsworth, S., Rudall, P., Bateman, R. & Glover, B.J. (2011) Characterisation of Linaria KNOX genes suggests a role in petal spur development. Plant Journal 608, 703-714. 

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