Abstract: The potato genes RB and R3a encode coiled-coil，nucleotide binding site，leucine-rich repeat（CC-NBS-LRR）proteins and confer specific recognition to AvrB and Avr3a effectors of the late blight pathogen Phytophthora infestans，manifested as a hypersensitive response（HR）at the initial site of infection. In this study，overexpression of RB and R3a were constructed by cloning coding domains to the vector which contains CaMV35S promoter. Chimerical constructs of domain swapping between R3a and its homolog I2GA1 in CC，NBS and LRR were generated by overlap extension polymerase chain reaction. The recognition capability of the overexpressing and domain swapping constructs to AvrB and Avr3a were tested by Agrobacterium transient transformation assay（ATTA）. The results showed that the expression of RB was much higher and HR appeared almost one day earlier under the control of CaMV35S promoter than the native one. For R3a，there was no difference of expression and HR observed under the control of these two kinds of promoter. Domain swapping revealed that the recognition specificity of R3a is mostly determined by the domain of LRR.

Key words: potato, late blight, over extension PCR, domain swapping, ATTA