Induction of defense genes are not affected by effect of auxin on harpin initiated cell death. (A) Expression of HIN1 mRNA. Northern blot using RNA from leaves infiltrated with lane 1: Buffer 4.5 h; lane 2: 50 μM 2,4-D 4.5 h; lane 3: Harpin 4.5 h; lane 4: Harpin + 50 μM 2,4-D 4.5 h; lane 5: Harpin + 50 μM 2,4-D 24 h; lane 6: harpin – necrotic (9 h); lane 7: 50 μM 2,4-D 24 h. (B) Expression of PR1 mRNA. Lane 1: Buffer 24 h; lane 2: 2,4-D 24 h; lane 3: harpin 24 h; lane 4: Harpin + 2,4-D 24 h. 10 μg total RNA per lane from infiltrated area (A) or 1 cm region surrounding the infiltrated region (B) were used for the analysis. For panel B, leaf tissue was collected from region surrounding the infiltrated region because PR1 was not induced in the infiltrated area at these time points. RNA extraction, sequence and preparation of probes and subsequent procedures used have been described earlier . rRNA bands of the RNA gel used for the Northern blot, visualized by staining with ethidium bromide, is shown in the lower frame of each panel.