Monitoring the expression patterns of potato genes associated with quantitative resistance to late blight during Phytophthora infestans infection using cDNA microarrays

To elucidate the molecular events of potato quantitative resistance to Phytophthora infestans, we performed a comprehensive transcriptional analysis using cDNA microarrays, containing 1009 ESTs from a subtractive library. Leaves of a moderately resistant potato clone were inoculated with P. infestans and sampled at nine time points ranging from 2 to 72 h after inoculation. A total of 348 P. infestans-responsive genes were identified. These functional genes are mostly related to metabolism, plant defense, signaling and transcription regulation, involving the whole process of plant defense response to pathogens. Based on the general expression patterns of these genes at different time points, we discriminated distinct stages of potato defense against P. infestans and revealed genes participating in each stage. To further understand the dynamics of P. infestans-induced gene expression, hierarchical clustering was used to illustrate their various expression profiles during the time course, including early, mid and late gene induction as well as early gene repression. Interestingly, some genes involved in the hypersensitive response were also identified, suggesting that a same or similar defense system may exist in both race-specific and race-nonspecific resistances. In addition, 114 novel genes with unknown functions were isolated.