Figure 1.

Pst prevents the induction of proteasome activity during basal defense in a T3SS-dependent manner. A, Proteasome activity in leaves of Arabidopsis plants infected with either Pst wild-type bacteria or a Pst ∆hrcC strain lacking a functional T3SS. Samples were taken 2 d post inoculation (dpi), and the relative proteasome activity was determined. Each bar represents the mean of three biological replicates ± sd. MgCl₂ infiltration serves as a mock control. Asterisks indicate statistical differences according to Student’s t test (***, P < 0.001) in comparison with the mock control. The experiment was repeated three times with similar results. B, Accumulation of ubiquitinated proteins in Arabidopsis leaves after infection with different Pst strains (top) and accumulation of the 20S subunit PBA1 (bottom). All experiments were carried out more than three times with similar results.