Chalcone Synthase Promoters in Petunia Are Active in Pigmented and Unpigmented Cell Types.

Abstract

Chalcone synthase (CHS) catalyzes the first step in the biosynthesis of flavonoids that function in flower pigmentation, protection against stress, and induction of nodulation. The petunia genome contains eight complete chs genes, of which four are differentially expressed in floral tissues and UV-light-induced seedlings. The 5[prime]-flanking regions of these four chs genes were fused to the [beta]-glucuronidase (GUS) reporter gene and introduced into petunia plants by Agrobacterium-mediated transformation. We show that expression of each construct is identical to the expression of the authentic chs gene, implying that the differences in expression pattern between these chs genes are caused at least in part by their promoters. Histochemical analyses of GUS expression show that chs promoters are not only active in pigmented cell types (epidermal cells of the flower corolla and tube and [sub] epidermal cells of the flower stem) but also in a number of unpigmented cell types (mesophylic cells of the corolla, several cell types in the ovary and the seed coat). Comparison of chs-GUS expression and flavonoid accumulation patterns in anthers suggests that intercellular transport of flavonoids and enzymes occurs in this organ. Analysis of the flavonoids accumulated in tissues from mutant lines shows that only a subset of the genes that control flavonoid biosynthesis in the flower operates in the ovary and seed. This implies that (genetic) control of flavonoid biosynthesis is highly tissue specific.

Gibberellin-regulated expression of a myb gene in barley aleurone cells: evidence for Myb transactivation of a high-pI alpha-amylase gene promoter.

“…Binding site selection studies showed that Myb.Ph3 recognizes a consensus sequence TAACTAACAAAA (opposite strand shown; Solano et al, 1995). l h e petunia chalcone synthase J gene promoter, which directs expression of a reporter gene predominantly in epidermal cells of petunia flower buds, contains two putative MYB.Ph3 binding sites (Koes et al, 1990;Solano et al, 1995). MYB.Ph3 has been demonstrated to be a transcriptional activator of the chalcone synthase promoter in tobacco protoplasts.…”

anthocyanin1 of Petunia Encodes a Basic Helix-Loop-Helix Protein That Directly Activates Transcription of Structural Anthocyanin Genes

“…However, the pigment responsible for the brown color of petunia seeds is unknown, although it can be converted into an anthocyanin (delphinidin) by treatment with mineral acid. That its synthesis requires some of the flower pigmentation loci, including an1, an11, and an6 (an6 contains the dfrA gene) (Koes et al, 1990), suggests that it may a be flavonoid polymer such as, for instance, condensed tannins or a phlobaphene. Thus, the interaction of AN1 with P1 may reflect interaction with an unknown MYB protein from petunia involved in pigmentation of the seed coat.…”

The an11 locus controlling flower pigmentation in petunia encodes a novel WD-repeat protein conserved in yeast, plants, and animals.

“…After one day incubation at 25°C, protein extracts were made by grinding the corolla in 400 btl 50 mM NaPi at pH 7.0, 2 mM EDTA, 20 mM DTT and 4% PVP. Luciferase activity was measured with the Luciferase Assay System (Promega Corp., WI), and GUS activity was measured as described (Koes et al 1990). Data are expressed as the ratio of arbitrary light units to arbitrary units of fluorescence.…”