show Abstracthide AbstractLate blight caused by Phytophthora infestans is one of the most devasting diseases in potatoes and tomatoes. At present, several late blight resistance genes have been mapped and cloned. In order to better understand the mechanism of defense response mediated by R3a against P.infestans. In this study, after spraying dexamethasone, the leaves of MM-R3a-Avr3a and MM-Avr3a transgenic plants at different time points (0-h, 2-h and 6-h) were used for comparative transcriptome analysis.