title: An operon for production of bioactive gibberellin A4phytohormone with wide distribution in the bacterial rice leaf streak pathogen Xanthomonas oryzae pv. oryzicola.
abstract: Phytopathogens have developed elaborate mechanisms to attenuate the defense response of their host plants, including convergent evolution of complex pathways for production of the GA phytohormones, which were actually first isolated from the rice fungal pathogen Gibberella fujikuroi. The rice bacterial pathogen Xanthomonas oryzae pv. oryzicola (Xoc) has been demonstrated to contain a biosynthetic operon with cyclases capable of producing the universal GA precursor ent-kaurene. Genetic (knock-out) studies indicate that the derived diterpenoid serves as a virulence factor for this rice leaf streak pathogen, serving to reduce the jasmonic acid-mediated defense response. Here the functions of the remaining genes in the Xoc operon are elucidated and the distribution of the operon in X. oryzae is investigated in over 100 isolates. The Xoc operon leads to production of the bioactive GA4, an additional step beyond production of the penultimate precursor GA9mediated by the homologous operons recently characterized from rhizobia. Moreover, this GA biosynthetic operon was found to be widespread in Xoc (> 90%), but absent in the other major X. oryzae pathovar. These results indicate selective pressure for production of GA4in the distinct lifestyle of Xoc, and the importance of GA to both fungal and bacterial pathogens of rice.
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, 50011, USA.
authors.forename: Raimund
authors.initials: R
authors.lastname: Nagel
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, São Paulo, Brasil.
authors.forename: Paula C G
authors.initials: PC
authors.lastname: Turrini
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, 50011, USA.
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Nett
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, 80523, USA.
authors.forename: Jan E
authors.initials: JE
authors.lastname: Leach
authors.affiliation: IRD - Cirad - Univ Montpellier, UMR Interactions Plantes Microorganismes Environnement (IPME), Montpellier, 34399, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Verdier
authors.affiliation: Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, São Paulo, Brasil.
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Van Sluys
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, 50011, USA.
authors.forename: Reuben J
authors.initials: RJ
authors.lastname: Peters
mesh_terms: D053898:Biosynthetic Pathways / Q000235:genetics; D005843:Geography; D005875:Gibberellins / Q000096:biosynthesis* / Q000737:chemistry; D009876:Operon / Q000235:genetics*; D012275:Oryza / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D018515:Plant Leaves / Q000382:microbiology*; D014974:Xanthomonas / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; C532593:gibberellin A4
keywords: biogeographical distribution; cytochromes P450; gibberellin biosynthesis; plant-microbe interactions; virulence factor