Chloroplast positioning and morphology during plant immunity
File(s)
Author(s)
Savage, Zachary
Type
Thesis
Abstract
Chloroplasts are the organelles that provide plants with chemical energy through photosynthesis. To survive and thrive, plants must not only harness energy for growth, but also repel infection by numerous pathogens. The plant immune system is complex and multi-layered, involving a co-ordinated response within each cell to provide the defences that prevent pathogen invasion. During infection, chloroplasts uptake roles in the plant immune system, particularly in the biosynthesis of signalling molecules and the production of antimicrobials. As well as this, chloroplasts produce stroma filled tubules (stromules) during immune challenge, displaying the plasticity of their morphology. They also gather around the nucleus of the cell, presumably to facilitate chloroplast-to-nucleus signalling to aid in launching the immune response. However, how chloroplasts relocate within the cell in relation to a pathogen remains unknown. Further, the signalling pathways that regulate stromules have not yet been explored, and the effect of chloroplast-nucleus association on the outcome of infection is also poorly understood. Here, I employ extensive quantitative confocal microscopy of the Solanaceous model plant Nicotiana benthamiana infected by the late-blight pathogen Phytophthora infestans to explore how chloroplast positioning and morphology changes during infection, and to investigate how these processes are regulated. I observe how chloroplasts reposition within the cell during infection in relation to both the haustoria of P. infestans and the plant cell nucleus, showing for that chloroplasts are associated with pathogen haustoria. I also define the first known signalling pathway that underpins stromule induction, opening the door for further research into stromules, who’s functions remain elusive. Finally, I investigate the unconventional role of a chloroplast movement protein, CHUP1, in the context of immunity, revealing how it is unexpectedly required for the proper deposition of cell wall-thickening callose at haustoria.
Version
Open Access
Date Issued
2022-05-31
Date Awarded
12/01/2022
License URL
Advisor
Bozkurt, Osman Tolga
Sponsor
Biotechnology and Biological Sciences Research Council (Great Britain)
Grant Number
BB/M011178/1
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)