title: Analysis of a chemical plant defense mechanism in grasses.
abstract: In the Gramineae, the cyclic hydroxamic acids 2,4-dihydroxy-1, 4-benzoxazin-3-one (DIBOA) and 2,4-dihydroxy-7-methoxy-1, 4-benzoxazin-3-one (DIMBOA) form part of the defense against insects and microbial pathogens. Five genes, Bx1 through Bx5, are required for DIBOA biosynthesis in maize. The functions of these five genes, clustered on chromosome 4, were demonstrated in vitro. Bx1 encodes a tryptophan synthase alpha homolog that catalyzes the formation of indole for the production of secondary metabolites rather than tryptophan, thereby defining the branch point from primary to secondary metabolism. Bx2 through Bx5 encode cytochrome P450-dependent monooxygenases that catalyze four consecutive hydroxylations and one ring expansion to form the highly oxidized DIBOA.
authors.affiliation: Institut für Genetik, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Frey
authors.forename: P
authors.initials: P
authors.lastname: Chomet
authors.forename: E
authors.initials: E
authors.lastname: Glawischnig
authors.forename: C
authors.initials: C
authors.lastname: Stettner
authors.forename: S
authors.initials: S
authors.lastname: Grün
authors.forename: A
authors.initials: A
authors.lastname: Winklmair
authors.forename: W
authors.initials: W
authors.lastname: Eisenreich
authors.forename: A
authors.initials: A
authors.lastname: Bacher
authors.forename: R B
authors.initials: RB
authors.lastname: Meeley
authors.forename: S P
authors.initials: SP
authors.lastname: Briggs
authors.forename: K
authors.initials: K
authors.lastname: Simcox
authors.forename: A
authors.initials: A
authors.lastname: Gierl
mesh_terms: D048588:Benzoxazines; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements; D017343:Genes, Plant; D006900:Hydroxylation; D007211:Indoles / Q000378:metabolism; D008969:Molecular Sequence Data; D010078:Oxazines / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism; D013379:Substrate Specificity; D014367:Tryptophan Synthase / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D048588:Benzoxazines; D004251:DNA Transposable Elements; D007211:Indoles; D010078:Oxazines; C104846:2,4-dihydroxy-1,4-benzoxazin-3-one; C030374:indole; D003577:Cytochrome P-450 Enzyme System; D014367:Tryptophan Synthase; C050733:2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one