CTSB and infection: A. thaliana cysteine proteases from the family C19 ubiquitin carboxyl-terminal hydrolase 12 and 13 (AtUBP12 and AtUBP13), appear to be negative regulators of plant immunity: they are able to suppress Cf-9-mediated HR in N. benthamiana following PstDC3000 infection through the possible deubiquitinylation of PRRs [57].