Prolonged Exposure to Low Temperature Results in an Increase in Immunity against Pst DC3000. Prolonged Exposure to Low Temperature Results in an Increase in Immunity against Pst DC3000. (A) Photograph of wild-type plants grown at either 22°C for 4 weeks (warm) or grown at 22°C for 4 weeks followed by 3 weeks at 4°C (3 wk cold). (B) Wild-type and C3 transgenic plants that had been grown at 22°C for 4 weeks (warm) or grown at 22°C for 4 weeks followed by 3 weeks at 4°C (3 wk cold) were inoculated with Pst DC3000 (OD600 = 0.0001). Bacterial growth was measured at 0 and 3 d postinoculation as described in Methods. Three biological replicates were performed; the figure shows a representative experiment. Error bars indicate sd (n = 4 [day 0] and n = 8 [day 3] technical replicates). An asterisk indicates a difference between warm and cold-treated plants (P < 0.05, Student’s t test). (C) Wild-type and C3 transgenic plants that had been grown at 22°C for 4 weeks (warm) or at 22°C for 4 weeks followed by 3 weeks at 4°C (3 wk cold) were inoculated with Pst DC3000 (DC3000) (OD600 = 0. 001) or treated with 10 mM MgCl2 (mock). Leaf tissue was collected at 24 h postinoculation. Transcript levels were determined by RT-qPCR as detailed in Methods. Data were subjected to ANOVA as described in Methods. Error bars indicate se (n = 3 biological replicates). Bars marked with different letters are significantly different (LSD, P < 0.05). Transgenic lines AV27, KE/AV6, and 334 #5 were used in the experiments. Yong Sig Kim et al. Plant Cell 2017;29:2465-2477 ©2017 by American Society of Plant Biologists