Supervisor
Dr Madelaine Bartlett
Overview:
Flowers rule our world agriculturally, culturally, and ecologically. This dominance arises, in part, from tremendous diversity in floral morphology. The evolution of development is an important driver in the evolution of floral morphology. However, developmental genes, and the fundamental aspects of floral organisation and architecture they regulate, are deeply conserved within species, families, and often entire orders (Specht & Bartlett, 2009). This deep conservation inhibits genetic dissection, where variation within crossable lineages is required for mechanistic dissection. Unisexual flowers present a powerful exception. Most flowers (>96%) are bisexual, producing pollen in stamens and ovules in pistils. However, floral unisexuality has evolved repeatedly and results in specialised staminate vs. pistillate flowers within a species (dioecy) or even within a single individual (monoecy). Importantly, this floral specialisation (1) often includes profound variation in floral organisation and architecture; (2) is genetically regulated; and (3) occurs within controlled genetic backgrounds (Schrager-Lavelle et al., 2017; Klein et al., 2022; Gallagher et al., 2023). Thus, the evolution of unisexual flowers provides a powerful framework for dissecting the genetic mechanisms underpinning the evolution of floral form.
In this project, the selected student will study the molecular and functional evolution of genes with known and hypothesized roles in the development and evolution of floral unisexuality. Insights from across angiosperm diversity will allow us to identify genes and genetic networks repeatedly targeted in the evolution of floral organisation and architecture, and to determine the developmental mechanisms underlying the evolution of floral morphology.
Importance of Research:
This project will reveal the fundamental developmental and genetic mechanisms underlying the evolution of morphological diversity. Additionally, since every fruit, including every grass grain, comes from a pollinated flower, the discoveries we make here have the potential for translational impact in agriculture.
Project Summary:
The student selected to work on this project will:
- Resolve the evolutionary histories of genes with known roles in unisexual flower development, and genes on described ‘sex determining regions’ using comparative phylogenetic methods, and identify molecular correlates of floral evolution (e.g. duplications, selection, conserved non-coding sequence evolution)
- Assess effects of select molecular correlates of floral evolution on developmental gene function, using Arabidopsis thaliana as an experimental test-bed.
- Test hypotheses of grass unisexual flower evolution using directed evolution in bisexual Brachypodium distachyon flowers.
What will the successful applicant do?
This project involves an integrative combination of comparative genomics, phylogenetics, and molecular development. Students will gain experience with a broad range of computational and wet lab techniques, as well as with quantitative phenotyping and genetic analysis in multiple plant systems.
References
Gallagher JP, Man J, Chiaramida A, Rozza IK, Patterson EL, Powell MM, Schrager-Lavelle A, Multani DS, Meeley RB, Bartlett ME. 2023. GRASSY TILLERS1 (GT1) and SIX-ROWED SPIKE1 (VRS1) homologs share conserved roles in growth repression. Proceedings of the National Academy of Sciences of the United States of America 120: e2311961120. DOI:10.1073/pnas.2311961120
Klein H, Gallagher J, Demesa-Arevalo E, Abraham-Juárez MJ, Heeney M, Feil R, Lunn JE, Xiao Y, Chuck G, Whipple C, et al. 2022. Recruitment of an ancient branching program to suppress carpel development in maize flowers. Proceedings of the National Academy of Sciences of the United States of America 119. DOI:10.1073/pnas.2115871119
Schrager-Lavelle A, Klein H, Fisher A, Bartlett M. 2017. Grass Flowers: An Untapped Resource for Floral Evo-Devo. Journal of systematics and evolution. DOI:10.1111/jse.12251
Specht CD, Bartlett ME. 2009. Flower Evolution: The Origin and Subsequent Diversification of the Angiosperm Flower. Annual review of ecology, evolution, and systematics 40: 217–243. DOI:10.1146/annurev.ecolsys.110308.120203annurev.ecolsys.110308.120203