Northern blot analysis of the expression pattern of salicylic acid- and jasmonic acid- regulated genes. (A) Northern blot analysis of the accumulation Pr1a, Pr1b, and LAP transcripts in 20 μg of total RNA extracted from healthy tomato (lane 1), PSTVd-infected tomato (Viroid-infected tomato, lane 2), non-transformed control (X, lane 3), transgenic plants XS (lane 4) and XAS (lane 5), and tomatoes infected with Potato virus X (PVX-infected tomato, lane 7). Ethidium bromide staining of ribosomal RNA (rRNA) is shown to illustrate equal loading of RNAs. SA, salicylic acid-inducible genes; JA-jasmonic acid-inducible gene. (B) Northern blot analysis of total RNA samples as in (A) using only the Pr1b probe. Lane 1, Healthy tomato; Lane 2, PSTVd-infected tomato; Lane 3, X; Lane 4, XS; Lane 5, XAS; Lane 6, PSTVd-infected Xanthi tobacco.