Differential gene expression in Arabidopsis leaves after Si treatment and/or pathogen inoculation. The columns represent the contrasts between the treatments: control (C), silicon (Si), E. cichoracearum (P), or a combination of both (Si-P). Each of the 3,970 differentially expressed genes (P < 0.01, ≥1.5-fold change) in at least one contrast is represented by a colored line indicating the mean (n = 6) relative transcript level: green corresponds to a log2 ratio of −2 (down-regulation), and red corresponds to a log2 ratio of 2 (up-regulation).