The role of DA1 in organ size control in Arabidopsis thaliana

Prior, Rachel (2017) The role of DA1 in organ size control in Arabidopsis thaliana. Doctoral thesis, University of East Anglia.

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Despite the sizes of organs and organisms being a key defining feature, very little is known about how the final sizes of organs is determined. Recent progress has highlighted the important role of the DA1 peptidase as a negative regulator of organ size in Arabidopsis thaliana. Previous studies have proposed that DA1, and the E3 ligase BIG BROTHER (a protein known to regulate DA1 activity), work synergistically to regulate the duration of cell proliferation. In the prulresent study, we take a multidisciplinary approach to further our understanding of the biological activities of DA1 and BB.

Protoplast transient expression analyses were used to explore potential new substrates for DA1 peptidase activity, and to work towards identifying a conserved target site for DA1mediated cleavage. Using confocal microscopy and bespoke segmentation software, I embarked on a global analysis of leaf cellular phenotypes in the da1-1, bb, and da1-1bb mutants throughout early development. This allowed a holistic comparison to wild type of parameters such as total cell number, and cell area, density, and circularity. In addition, scanning electron microscopy was used to examine cells in mature leaves of wild type, and da1-1, bb, and da1-1bb mutants, revealing novel insights into the control of final organ size in these mutants relative to wild type. Finally, innovative live cell imaging has, for the first time, allowed cell divisions to be observed in plants carrying the da1-1, bb, and da1-1bb mutations. My observations and interpretation establish new insights into how DA1 and BB control growth by controlling the arrest of cell proliferation, and the population-level rate of cell proliferation. The approaches I have developed show the promise of quantitative cell imaging for understanding organ growth, and establish a framework for precisely comparing the effects of different mutations on organ growth.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Bruce Beckett
Date Deposited: 23 Jul 2018 14:52
Last Modified: 01 Jun 2020 00:38


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