The proteins found at plasmodesmata and the interactions between them

Johnston, Matthew (2021) The proteins found at plasmodesmata and the interactions between them. Doctoral thesis, University of East Anglia.

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Plasmodesmata are specialised membrane-lined pores that create cell-to-cell connections through the cell wall. This cytoplasmic and membrane continuity allows for communication and co-ordination between cells, a prerequisite for multicellularity. All land plants contain plasmodesmata derived from a single evolutionary event.

Plasmodesmata are not passive conduits. Instead, the aperture of plasmodesmata is dynamically regulated by the deposition of a complex carbohydrate, callose. This controls the cell-to-cell flux through plasmodesmata.

In this thesis, I explore the protein composition of plasmodesmata. I developed a plasmodesmata extraction protocol for mature plant tissue. This protocol is used to biochemically localise transiently expressed proteins to plasmodesmata in Nicotiana benthamiana. This technique is then extended to define the native plasmodesmal proteome of the bryophyte Physcomitrella patens. I used a comparative phyloproteomic approach to identify conserved protein families at plasmodesmata. This approach identified two classes of structural proteins, C2 lipid-binding proteins and tetraspanins, which may have been present in the plasmodesmata of the last common ancestor between land plants and algae.

Secondly, I investigate interactions between PLASMODESMATA-LOCALISED PROTEINs (PDLPs) and other plasmodesmata proteins. PDLP overexpression leads to the misregulation of callose deposition, ultimately dwarfing Arabidopsis thaliana plants. I exploited this phenotype to find novel components in the PDLP-callose deposition pathway. Ultimately, I propose a common pathway downstream of PDLPs which is required for plasmodesmata callose deposition.

Overall, the results herein offer candidate proteins that may be ancient components of plasmodesmata. These may have both structural and biochemical functions. I characterised one PDLP interactor, NDR1/HIN1-LIKE 3, and produced a list of other likely interactors, by comparing interaction data with A. thaliana plasmodesmal proteomes. An additional putative genetic interactor with PDLP1, KISS ME DEADLY 2, was identified by a forward genetic screen. This will guide the direction of future investigations.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 27 Oct 2021 08:48
Last Modified: 31 Jan 2022 01:38


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