Plants Under Pressure: A Joint Experimental-Theoretical Investigation of the Plant Response to Local Stimuli

Abstract

Rising temperatures and growing populations are putting increased pressure on food sources, with pathogens moving polewards in search of more favourable conditions. Stopping crop losses due to disease would provide enough additional food to solve world hunger, with spare left over. My PhD has been centred on discovering more about how plants are able to defend themselves to new or unknown potential pathogens through the use of the model organism, Arabidopsis thaliana. I have helped to develop a novel method of stimulating the basal immune response in order to probe different components of this system.

PEN3, a key defence protein that is transported to the site of infection, was observed over the initial 20 minutes of an immune response and its accumulation was quantified. PEN3 transport requires the actin cytoskeleton, which remodels within 30s of artificial peg contact, therefore I developed an image analysis algorithm to segment and quantify various aspects of the cytoskeletal network. This algorithm detected significant differences in the network of loss-of-function mutants of arp2-1 and formin4/7/8 compared to the wildtype, yet the PEN3 distributions were functionally identical. These findings, alongside simulations of PEN3 accumulation with various delivery zone sizes led to the hypothesis of at least one upstream signalling molecule designating PEN3 secretion into the membrane.

The novel assay, network extraction tool and PEN3 simulations are discussed in detail, including their limitations and potential improvements as well as other systems they could be applied to.