Transcriptome analysis of phosphonate-pretreated tomato in response to inoculation with Phytophthora parasitica

Phosphonate related fungicides such as neutralized phosphorous acid (NPA) are effective for the control of plant diseases caused by Oomycetes including Phytophthora parasitica. It has been proposed that phosphonate may induce plant resistance. However, the mechanism underlying phosphonate-induced resistance remains unclear. The purpose of this study is to identify genes that are differentially expressed in phosphonate-pretreated tomato plants in response to inoculation with Phytophthora parasitica. We treated the tomato plants with NPA or water (ddH2O, as a control) for three days, and then inoculated the plants with zoospores of P. parasitica. For microarray analysis by the use of Affymetrix Tomato Genome Array, total RNAs were isolated from plant leaves at: (1) 3 days post treatment (dpt) with NPA or water, (2) 6 hours post inoculation (hpi) of the NPA- or water-pretreated plants, (3) 12 hpi of the NPA- or water-pretreated plants. To reduce the biological variability, each hybridization experiment was performed with RNA prepared from pools of five plants. The total set of experiments was repeated three times.