title: Regulation and manipulation of flavonoid gene expression in anthers of petunia: the molecular basis of the Po mutation.
abstract: Molecular mechanisms governing development of the male reproductive organs of flowers, the anthers, are largely unknown. In this article, we report on the investigation of the molecular basis of a mutation involving the expression of a gene encoding the flavonoid biosynthesis enzyme chalcone flavanone isomerase (CHI) in anthers of petunia. In petunia, the gene Po regulates the expression of CHI in anthers: PoPo petunia lines contain CHI enzyme activity in petals and anthers, whereas popo lines contain the CHI enzyme only in petals but not in anthers. As a result of the Po mutation, the substrate of CHI accumulates and therefore the pollen of a popo line are yellow or greenish. The genome of petunia contains two chi genes, chiA and chiB. In a restriction fragment length polymorphism analysis, a 100% linkage was observed between Po and chiA. This result suggested that Po is identical to chiA and that Po is not a regulatory gene of chiA. Introduction of a chiA gene isolated from a PoPo line into a popo line resulted in a complementation of the mutation that was directly visible because the pollen color shifted from yellow to white. This proved that chiA and Po are identical. Because chiA encodes a functional CHI enzyme in flower petals of a popo line, we propose that the Po mutation is a mutation in the regulatory region of chiA abolishing chiA promoter activity in anthers but not in corollas. This change in anther color is a fine illustration of how floral pigmentation can be manipulated in a predictable way and suggests the use of CHI as a visible marker.
authors.affiliation: Department of Genetics, Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: van Tunen
authors.forename: L A
authors.initials: LA
authors.lastname: Mur
authors.forename: K
authors.initials: K
authors.lastname: Recourt
authors.forename: A G
authors.initials: AG
authors.lastname: Gerats
authors.forename: J N
authors.initials: JN
authors.lastname: Mol
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015971:Gene Expression Regulation, Enzymologic; D005816:Genetic Complementation Test; D008040:Genetic Linkage; D019753:Intramolecular Lyases; D007535:Isomerases / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010944:Plants / Q000201:enzymology / Q000235:genetics*
chemical_list: D007535:Isomerases; D019753:Intramolecular Lyases; C019865:chalcone isomerase