Abstract
dc:description.abstractAngiosperms often exhibit various patterns on their petals. These patterns allow entomophilous plants to attract pollinators and also help them deal with abiotic stress such as UV-levels and water loss. While previous research largely focused on pigmentation patterns, structural patterns created by the combination of different cell shapes have also been observed. However, why and how plants create these structural patterns remains largely unknown. My PhD project aims to investigate the development of petal structural patterns and explore their possible ecological significance. In the first part of my thesis, I surveyed the living collections at Cambridge University Botanic Garden to examine whether structural patterns (changes in cell shapes) across the petal epidermis are common among angiosperm families. Bumblebee experiments were also conducted to test whether pollinators can distinguish between a structural-patterned petal surface and a petal surface without cell shape patterns. In the second part of my thesis, I tried to identify possible regulators for the development of different petal epidermal cell shapes. Hibiscus trionum has been developed as a novel model species to investigate petal patterning: its flowers produce conical cells in the petal distal region and flat polygonal cells in the petal proximal region, constituting an excellent system for investigating the different mechanisms underlaying the patterned production of two distinct cell shapes across the petal epidermis. In this section, I first used a candidate gene approach based on the literature and transcriptomic data previously generated by the Moyroud Group to select potential candidate transcription factors. I then generated constitutive overexpression lines and CRISPR/Cas9 knock-out lines for these candidate genes to explore their possible functions during H. trionum petal development and clarify their contribution, if any, to petal cell shape specification. In parallel, I also characterised the development of an EMS-induced mutant (named ‘madeleine’) with defects in cell shapes. Transcriptome data generated by me and analysed by a post-doc in the Moyroud Group revealed that a single point mutation in a UGT (UDP- glucuronosyltransferases) gene accounts for the madeleine phenotype and that this effect is mediated, in part, through changes in expression levels of genes known to regulate the production of epidermal cell features (pigmentation, cuticular striation and cell shape). In the last part of my thesis, I generated fluorescent reporter lines for cytoskeleton components (actin filaments and microtubules) and two SOSEKI family polar proteins. It is known that cytoskeleton and polar proteins contribute to the polarised growth of cells and thus should play a key role in the production of distinct cell shapes across the petal surface. I then used these reporter lines to visualise the behaviour of the cytoskeleton and track the emergence of cell polarity when cell shapes differentiate during petal development in both wild type H. trionum and mutants or transgenic lines with defective cell shapes. In brief, my thesis revealed the frequent existence of petal structural patterns among angiosperms that can be perceived by pollinators and identified several genes that influence cell shape specification during petal development. My PhD work also generated useful resources to link gene activity to cell behaviour and established solid foundations for future studies aiming to uncover the gene regulatory networks and cellular processes that control the development of contrasting cells shapes within a single tissue.
Degree
thesis:*- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2025
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Liang, Yuxi
- Advisor dc:contributor.advisor
-
- Moyroud, Edwige
Subjects
dc:subject × 4Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.121070
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/388944