Recombinant GST-AvrPtoB protein was expressed in and purified from E. coli with glutathione-Sepharose resin. GST-AvrPtoB was incubated with leaf extracts in the presence of [γ-32P]ATP and separated by 10% SDS-PAGE, followed by autoradiography. Incorporation of 32P into GST-AvrPtoB (top panel) occurred in the presence of leaf extracts from tomato lines RG-PtoR (PtoR), RG-prf3 (prf3), RG-pto11 (pto11), N. benthamiana (Nb), and A. thaliana Columbia-0 (At). Equal loading of GST-AvrPtoB protein was verified by Coomassie Blue staining (bottom panel).