title: Analysis of the developmental roles of the Arabidopsis gibberellin 20-oxidases demonstrates that GA20ox1, -2, and -3 are the dominant paralogs.
abstract: Gibberellin (GA) biosynthesis is necessary for normal plant development, with later GA biosynthetic stages being governed by multigene families. Arabidopsis thaliana contains five GA 20-oxidase (GA20ox) genes, and past work has demonstrated the importance of GA20ox1 and -2 for growth and fertility. Here, we show through systematic mutant analysis that GA20ox1, -2, and -3 are the dominant paralogs; their absence results in severe dwarfism and almost complete loss of fertility. In vitro analysis revealed that GA20ox4 has full GA20ox activity, but GA20ox5 catalyzes only the first two reactions of the sequence by which GA(12) is converted to GA(9). GA20ox3 functions almost entirely redundantly with GA20ox1 and -2 at most developmental stages, including the floral transition, while GA20ox4 and -5 have very minor roles. These results are supported by analysis of the gene expression patterns in promoter:β-glucuronidase reporter lines. We demonstrate that fertility is highly sensitive to GA concentration, that GA20ox1, -2, and -3 have significant effects on floral organ growth and anther development, and that both GA deficiency and overdose impact on fertility. Loss of GA20ox activity causes anther developmental arrest, with the tapetum failing to degrade. Some phenotypic recovery of late flowers in GA-deficient mutants, including ga1-3, indicated the involvement of non-GA pathways in floral development.
authors.affiliation: Plant Science Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom.
authors.forename: Andrew R G
authors.initials: AR
authors.lastname: Plackett
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Powers
authors.forename: Nieves
authors.initials: N
authors.lastname: Fernandez-Garcia
authors.forename: Terezie
authors.initials: T
authors.lastname: Urbanova
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Takebayashi
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Seo
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Jikumaru
authors.forename: Reyes
authors.initials: R
authors.lastname: Benlloch
authors.forename: Ove
authors.initials: O
authors.lastname: Nilsson
authors.forename: Omar
authors.initials: O
authors.lastname: Ruiz-Rivero
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Phillips
authors.forename: Zoe A
authors.initials: ZA
authors.lastname: Wilson
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Thomas
authors.forename: Peter
authors.initials: P
authors.lastname: Hedden
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000096:biosynthesis; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010802:Phylogeny; D051479:Plant Infertility; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000254:growth & development
chemical_list: D029681:Arabidopsis Proteins; D005875:Gibberellins; D006899:Mixed Function Oxygenases; C089210:gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)