PhERF1 regulates newly predicted genes involved in sterol biosynthesis. A) Diagram of sterol biosynthesis and related pathways. Petunia biosynthesis genes involved in the pathways (Table S6) were predicted based on similarities to their tomato counterparts (Table S5). The genes are represented as boxes placed beside enzyme abbreviations (see Table S5); red and blue boxes represent genes up-regulated and down-regulated by PhERF1, respectively. Downstream of cycloartenol, cholesterol-specific genes are shown in blue; phytosterol-specific genes are shown in red, and genes involved in both pathways are in purple. Petunia-specific steroids, such as petuniolides and petuniasterones, are presumed to be produced through a downstream branch that starts with a reaction mediated by sterol 24ISO. B) and C) Heatmap visualization of the expression levels of PhERF1-regulated genes shown in A and genes present in clusters Ai, Bi, Ci, and Da (see Fig. 3). 24ISO genes are included in C. Please refer to Table S5 or Fig. 3 for gene names and labels. Normalized expression values obtained in leaves transiently overexpressing PhERF1 are shown. PhERF1-down-regulated genes are marked with asterisks.