The expression patterns of Cucumis sativus WRKY (CsWRKY) family under the condition of inoculation with Phytophthora melonis in disease resistant and susceptible cucumber cultivars

Based on RNA-seq, we analyzed expression patterns of 55 CsWRKYs in the disease-resistant cultivar (JSH) and the disease-susceptible cucumber cultivar (B80) at 0 and 40 h post-inoculation with Phytophthora melonis. After inoculation with P. melonis, in JSH and B80, the number of up-regulated CsWRKY genes was both 25 with 22 commonly up-regulated genes, and there were 22 CsWRKY genes down-regulated in JSH and 23 in B80 with 18 commonly down-regulated genes, and there were eight CsWRKY genes with no or little change in transcript expression in JSH and seven in B80 with four common genes. Among the 55 CsWRKY genes, 17 genes showed significant differences (differences > twofold) in the degree of change of gene transcription level between JSH and B80 from RNA-seq data analysis, and the results validated using real-time PCR showed that there were only six genes (CsWRKY2, 20, 26, 35, 44, 52) out of the 17 that exhibited significant differences (differences > twofold) with four genes (CsWRKY2, 20, 26, 52) consistent with the data from RNA-seq and two genes (CsWRKY 35, 44) inconsistent with the data from RNA-seq. In addition, the six genes were strongly up-regulated after salicylic acid (SA) treatment with five genes (CsWRKY2, 20, 26, 35, 44) up to peak at 12 h and one gene (CsWRKY52) up to peak at 24 h in expression and that four CsWRKY genes (CsWRKY2, 20, 44, 52) out of six were strongly up-regulated with three genes (CsWRKY2, 20, 44) up to the highest point at 24 h and one gene (CsWRKY52) up after methyl jasmonate (MeJA) treatment. Based on the results above, we predicted CsWRKY2, 20, 26, 35, 44 and 52 may be involved in disease resistance of JSH against Phytophthora melonis by SA and (or) JA signaling pathway(s).