REGULATORY GENES-CONTROLLING ANTHOCYANIN PIGMENTATION ARE FUNCTIONALLY CONSERVED AMONG PLANT-SPECIES AND HAVE DISTINCT SETS OF TARGET GENES

In this study, we demonstrate that in petunia at least four regulatory genes (anthocyanin-1 [an1], an2, an4, and an11) control transcription of a subset of structural genes from the anthocyanin pathway by using a combination of RNA gel blot analysis, transcription run-on assays, and transient expression assays. an2(-) and an11(-) mutants could be t ransiently complemented by the maize regulatory genes Leaf color (Lc) or Colorless-1 (C1), respectively, whereas an1(-) mutants only by Lc a nd C1 together. In addition, the combination of Lc and C1 induces pigm ent accumulation in young leaves. This indicates that Lc and C1 are bo th necessary and sufficient to produce pigmentation in leaf cells. Reg ulatory pigmentation genes in maize and petunia control different sets of structural genes. The maize Lc and C1 genes expressed in petunia d ifferentially activate the promoters of the chalcone synthase genes ch sA and chsJ in the same way that the homologous petunia genes do. This suggests that the regulatory proteins in both species are functionall y similar and that the choice of target genes is determined by their p romoter sequences. We present an evolutionary model that explains the differences in regulation of pigmentation pathways of maize, petunia, and snapdragon.