Transcriptomic analysis reveals distinct strategies of two potato cultivars against Phytophthora infestans and identifies StWRKY26 as a positive regulator of late blight resistance

Late blight caused by Phytophthora infestans seriously threatens world’s potato production. Understanding the responsive mechanism of potato to P. infestans infection and exploring key regulators would be advantageous for improving the late blight resistance. Here, we firstly assessed the late blight resistance of 10 potato cultivars collected from Liangshan Yi Autonomous Prefecture and found that Chuan Liang Shu (CLS) is highly resistant, while Bu Wu Yu (BWY) is extremely susceptible. Comparative transcriptomics further revealed distinct mechanisms of CLS and BWY in response to P. infestans infection, in which CLS activates defense pathways rapidly, while BWY prioritizes energy towards growth and development pathways. Specifically, the up-regulated genes in CLS were largely enriched in oxidation-reduction process and SA-related pathways, resulting in activated ROS-scavenging systems and SA signaling. Clustering analysis for the expression patterns of transcription factors (TFs) demonstrates that the WRKY family members were significantly enriched in a cluster that is specifically induced in CLS after P. infestans infection. Silencing StWRKY26, one of the four WRKYs with higher induction levels, significantly compromise the intrinsic resistance against P. infestans in CLS. Our study enriches the knowledge of transcriptional responses of potato under P. infestans infection and provide candidate genes for breeding potato cultivars with strong late blight resistance.