Investigating the regulation of plant immunity by the N-degron pathway

Crop losses arising from plant diseases present a major obstacle for efforts to meet the food demands of a growing global population, and these impacts may be exacerbated by unprecedented rates of climate change. The Ubiquitin Proteasome System (UPS) contributes to the regulation of plant immunity and a greater understanding of its role in these processes could lead to the future development of disease-resistant crops. The N-degron pathway is a subset of the UPS that relates the stability of a protein to the identity of its N-terminal amino acid residue. Previous work has revealed distinct roles for the N-degron pathway as a regulator of plant defence responses (De Marchi et al., 2016; Gravot et al., 2016; Vicente et al., 2018), although the molecular mechanisms underpinning this activity are not fully understood. My project aims to elucidate the contribution of specific N-degron pathway enzymatic components to immunity through complementary approaches in Arabidopsis thaliana. These include (i) treatments with purified pathogen-associated molecular patterns (PAMPs) to unravel the role of the N-degron pathway in pattern triggered immunity (PTI) and (ii) inoculations with the model pathogen Pseudomonas syringae pv. tomato DC3000. Furthermore, this project aims to establish a foundation for N-degron pathway studies in the economically important crop Brassica rapa and transfer knowledge obtained via the experiments with its close relative Arabidopsis. Together, this work has yielded novel insights into the role of the N-degron pathway in the PTI response of both the Arabidopsis thaliana model and Brassica rapa, and may indicate the molecular mechanisms underlying its contribution to the pathogen response. These findings should be considered during future efforts to engineer more resilient crops to ensure global food security