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Development of the light-focusing prism cells of California poppy

Postgraduate project

Supervisor: Beverley Glover (Plant Sciences)

Project outline:

glover 2This project aims to understand how the unusual prism cells on the petal epidermis of Eschscholzia californica, the California poppy, develop. The petal epidermis of this flower consists of prism-like cells in which the ridge of the prism is filled with cell wall material. This is highly unusual as petal epidermal cells tend to be domed or conical in shape, composed primarily of vacuolar material, with only a thin cell wall. The prism cells focus incident light onto the carotenoid pigments found in the petal, located at the cell base. Using cell wall to fill the top of the prism ensures that light is focused to the base of the cell, not to the centre, and so reaches the plastid-containing pigments. This novel cell morphology has not been described in any other system, and we do not know how it is built.

In this project you will analyse how the prism cells develop, taking approaches which bring different training opportunities:

  1. We will analyse the other 11 species of Eschscholzia to establish whether other species share the trait and to assess whether it has evolved once or repeatedly within the genus. If there are non-prims cell species we will explore the possibility of crossing species and the segregation of the trait in the progeny.  TRAINING: light microscopy, scanning electron microscopy, phylogeny reconstruction, ancestral state analysis, genetics.
  2. We will explore the development of the prism cells in California poppy using a candidate gene approach. We will select a small number of candidate genes that we suspect might have a role in prism cell development and explore whether they are expressed in the developing prisms. For appropriate genes we will use transgenic approaches to downregulate their activity and analyse the consequences for prism cell development. TRAINING: qRT-PCR, transgenic approaches, molecular biology.
  3. For sister species with/without prism cells, or for early/late stage petals before/during prism cell development, we will compare all genes expressed in the petals using RNAseq, to describe the general gene expression network in a developing prism. This might also generate candidate genes to feed back into (2). TRAINING: RNAseq, analysis of transcriptomic data.
  4. We will use our bee behavioural lab to explore the response of foraging bumblebees to some of (a) pairs of species with and without prism cells; (b) transgenic and control lines with and without prism cells; (c) artificial surfaces with and without prism cells. TRAINING: bee behavioural experiments.

References

  1. Bodo D Wilts, Paula J Rudall, Edwige Moyroud, Tom Gregory, Yu Ogawa, Silvia Vignolini, Ullrich Steiner, Beverley J Glover (2018) Ultrastructure and optics of the prism‐like petal epidermal cells of Eschscholzia californica (California poppy). New Phytologist 219, 1124-1133.

 

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