Ubiqutin Proteasomes System (UPS) - an Intriguing Weapon of Plants and It's Modification by Plant Pathogens as Virulence Mechanism

Plants' ubiquitin-26S proteasome degradation system (UPS) is involved in the signal transduction of numerous cellular functions, including pathogen-triggered host immunological responses. Pathogens that attack create effectors that are translocated into host cells and disrupt defensive signals in the host in specific ways. Certain bacterial effectors, which are presently best understood in Pseudomonas syringae, exploit or depend on the host UPS for their activity, which may not come as a surprise given the extensive role of the host proteasome in plant immunology. Interestingly, certain strains of P. syringae express syringolin A, a virulence factor that uses a unique mechanism to irreversibly block the proteasome. This section summarizes the UPS's defense function for plants and how effectors use it. It also covers the biology, taxonomic distribution, and emerging implications for virulence strategies of syringolin A and similar compounds.