Lect. 5 Host Pathogen interaction-II

E. The transmembrane RLP Cf-2 guards the
extracellular cysteine protease Rcr3. Cf-2
recognizes the C. fulvum extracellular
effector Avr2, which encodes a cysteine
protease inhibitor. Avr2 binds and inhibits
the tomato Rcr3 cysteine protease.
Mutations in Rcr3 result in the specific loss
of Cf-2-dependent recognition of Avr2.
Hence, Cf-2 seems to monitor the state of
Rcr3, and activates defence if Rcr3 is
inhibited by Avr2.