Modelling and re-engineering the ubiquitin-proteasome system to engineer novel plant disease resistance (360G-Wellcome-316375_Z_24_Z)

Repurposing cellular machinery for novel functions, rather than improving existing function, is an underutilised approach to genetic engineering. In plants, immune receptors are frequently evaded by pathogen effector proteins that cause infection by dysregulating host biology. The Ubiquitin-Proteasome System (UPS), the central protein degradation pathway of the cell, offers an orthologous means to control infection by degrading pathogen effector proteins. In medicine, small molecules (PROTACs and molecular glues) have been developed that bring undruggable targets into proximity of the UPS E3 ligase that adds a ubiquitin signal, marking the target for degradation. However, these exogenous degraders lack applicability due to issues of bioavailability and discoverability. Instead, we aim to achieve targeted protein degradation in plants by re-engineering native proteins. By modifying the substrate- binding domain of plant E3 ligases, we look to alter their specificity to bind, ubiquitinate and thereby target effectors for degradation. To characterise this engineered knockdown, we will incorporate in vitro and plant data to parameterise ordinary differential equation models. These predictive, quantitative models will lead to more informed choices when engineering the UPS. Our model can then be used in other applications degrading novel targets to the interconnected benefit of plant and human health.