Gene expression of SA- and JA-responsive genes in transgenic Arabidopsis npr1-2 mutants. A. Semi-quantitative RT-PCR was performed with cDNA prepared from leaves of 4-week-old plants of wild type(C), npr1-2 (n) and 5 independent transgenic npr1-2 mutant lines overexpressing TcNPR1 (1-5). The expression of TcNPR1, AtPR1, AtVSP2 and AtPDF1.2 was evaluated 48 hrs after treatment with water control, 1 mM SA water solution alone, 0.1 mM MeJA alone in 0.015% Silwet L-77 and the combination of 1 mM SA and 0.1 mM MeJA in 0.015% Silwet L-77. AtUbiquitin was used as a cDNA loading and normalization control. B. The intensity of AtVSP2 and AtPDF1.2 RT-PCR gel bands in Figure 6A were quantified by ImageQuant software for total pixel intensity and the expression levels were normalized by AtUbiquitin. The bar charts represent the means ± standard errors of relative expression value of AtVSP2 and AtPDF1.2 following 48 hrs treatment of SA-MeJA combination of three biological replicates. Letters above the bar chart indicate statistically significant differences among genotypes (P < 0.05) determined by single factor ANOVA.