Abstract
Plant shape is determined by developmental programmes which result in distinct plant morphologies across land plants, which are thought to have diverged from the Charophycean algae around 500 million years ago. Polarised growth axes help regulate growth in early plant development and can be defined through the differential distribution of signalling molecules both locally and globally across plant tissues. Growth as a flattened mat of indeterminately growing tissue called the thallus characterises growth in the early diverging land plant group called liverworts. This ancient plant architecture makes liverworts suitably positioned in the phylogeny of land plants to answer questions on fundamental plant biology.Prior work has shown that thallus shape in a liverwort model system, Marchantia polymorpha, can be explained using a modelling approach. However, such computational approach could not describe some naturally observed elongated thalli shapes in other liverwort species. Here, results from a previously conducted but updated modelling approach incorporating polarity are included to set hypotheses for M. polymorpha growth.
Using pharmacological treatments and previously generated M. polymorpha lines which have been genetically engineered, I test modelling hypotheses and show through quantification and analysis of thalli phenotypes that phytohormones auxin and cytokinin are involved in polarity specification via PINs in M. polymorpha. In addition to growth experiments, I used a confocal approach to screen and explore PIN-GFP lines to identify the localisations of PIN proteins across the M. polymorpha thallus.
When both experimental approaches are taken together, my results identify the roles for polarity on thallus growth involving feedback between phytohormones auxin and cytokinin and explore which polarity modelling hypotheses generated by modelling best explain the growth observed in M. polymorpha thalli. I also suggest future work towards a more complete understanding of shape determination during M. polymorpha development.
| Date of Award | 2 Dec 2021 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Jill Harrison (Supervisor) |
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