Investigating Pattern Triggered Immunity in Arabidopsis thaliana Upon Botrytis cinerea Infection and the Role of SUMOylation in This Signalling Pathway

Abstract

Fungal disease in agriculture poses a significant risk to global food security. The development of crops that are resistant to fungal infection is central to addressing this challenge. Botrytis cinerea is a pathogenic fungus that causes grey mould disease in over 200 crop species, causing mass economic and agricultural losses. During B. cinerea infection in Arabidopsis thaliana, chitin from the fungal cell wall is sensed by a transmembrane protein called CERK1. CERK1 transduces a signal to the rest of the cell to initiate pattern triggered immunity (PTI) defences against the invading fungal pathogen. SUMOylation is a type of post-translational modification that is involved in many types of stress response and has been shown to also play a role in immunity during fungal infection. The goal of this research project was to gain a deeper understanding of plant PTI and to shed light on the potential role of SUMOylation in this signalling pathway during B. cinerea infection. After discovering that CERK1 constructs that were to be used in this project contained unintended mutations, CERK1 was re-cloned and SUMO-site mutations were re-inserted. Using the new CERK1 wild type (CERK1WT) and the CERK1 double SUMO-site mutant (CERK12KR) constructs in co-immunoprecipitation assays with SUMO1, it was determined that both CERK1WT and CERK12KR are SUMOylated upon chitin elicitation. Using fungal spore infection assays, it was confirmed that CERK1 is an essential protein for plant immunity upon B. cinerea infection due to greater lesion development in the CERK1 knockout transgenic line than in wild type plants. It remains unclear whether SUMOylation of CERK1 is essential for initiating an immune response to B. cinerea infection, and this is a recommended route for further investigation into this research.