MSc Exit Seminar- Diana Bonea

Investigation of proteasome architecture, activity, and interactors in Arabidopsis thaliana under abiotic stresses

Abstract:

The 26S proteasome plays a critical role in protein homeostasis via turnover of cellular proteins. Changes in subunit expression, assembly/disassembly of the holoenzyme, and association of non-canonical activators or inhibitors can fine-tune proteasome activity, although such pathways have not been explored in plants. This thesis examines the influence of abiotic stresses on structure, function, and interactors of the Arabidopsis thaliana proteasome. I found that oxidation and salinity decreased the cellular ratio of 26S to 20S proteasomes, altered proteasome subunit composition, and reduced binding of proteasome-associated proteins (PAPs) such as heat-shock and assembly chaperones. Additionally, oxidative stress specifically activated the 20S proteasome; a process which might be promoted by ATP deficiency. Further characterization of PAPs revealed that PBAC1, a 20S assembly chaperone, dampens oxidative damage to the germinating seed. Overall, findings suggest that regulation of proteasome activity, either through PAPs or ATP availability, is necessary for appropriate stress responses in Arabidopsis.

(Zhao & Gazzarrini Lab)