title: Genetic analysis reveals that C19-GA 2-oxidation is a major gibberellin inactivation pathway in Arabidopsis.
abstract: Bioactive hormone concentrations are regulated both at the level of hormone synthesis and through controlled inactivation. Based on the ubiquitous presence of 2beta-hydroxylated gibberellins (GAs), a major inactivating pathway for the plant hormone GA seems to be via GA 2-oxidation. In this study, we used various approaches to determine the role of C(19)-GA 2-oxidation in regulating GA concentration and GA-responsive plant growth and development. We show that Arabidopsis thaliana has five C(19)-GA 2-oxidases, transcripts for one or more of which are present in all organs and at all stages of development examined. Expression of four of the five genes is subject to feed-forward regulation. By knocking out all five Arabidopsis C(19)-GA 2-oxidases, we show that C(19)-GA 2-oxidation limits bioactive GA content and regulates plant development at various stages during the plant life cycle: C(19)-GA 2-oxidases prevent seed germination in the absence of light and cold stimuli, delay the vegetative and floral phase transitions, limit the number of flowers produced per inflorescence, and suppress elongation of the pistil prior to fertilization. Under GA-limited conditions, further roles are revealed, such as limiting elongation of the main stem and side shoots. We conclude that C(19)-GA 2-oxidation is a major GA inactivation pathway regulating development in Arabidopsis.
authors.affiliation: Centre for Crop Genetic Improvement, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom.
authors.forename: Ivo
authors.initials: I
authors.lastname: Rieu
authors.forename: Sven
authors.initials: S
authors.lastname: Eriksson
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Powers
authors.forename: Fan
authors.initials: F
authors.lastname: Gong
authors.forename: Jayne
authors.initials: J
authors.lastname: Griffiths
authors.forename: Lindsey
authors.initials: L
authors.lastname: Woolley
authors.forename: Reyes
authors.initials: R
authors.lastname: Benlloch
authors.forename: Ove
authors.initials: O
authors.lastname: Nilsson
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Thomas
authors.forename: Peter
authors.initials: P
authors.lastname: Hedden
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Phillips
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005638:Fruit / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics / Q000502:physiology; D005875:Gibberellins / Q000378:metabolism*; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008957:Models, Genetic; D010084:Oxidation-Reduction; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018547:Plant Stems / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D005875:Gibberellins