title: A plastid envelope location of Arabidopsis ent-kaurene oxidase links the plastid and endoplasmic reticulum steps of the gibberellin biosynthesis pathway.
abstract: We have used fusions of gibberellin biosynthesis enzymes to green fluorescent protein (GFP) to determine the subcellular localization of the early steps of the pathway. Gibberellin biosynthesis from geranylgeranyl diphosphate is catalysed by enzymes of the terpene cyclase, cytochrome P450 mono-oxygenase and 2-oxoglutarate-dependent dioxygenase classes. We show that the N-terminal pre-sequences of the Arabidopsis thaliana terpene cyclases copalyl diphosphate synthase (AtCPS1) and ent-kaurene synthase (AtKS1) direct GFP to chloroplasts in transient assays following microprojectile bombardment of tobacco leaves. The AtKS1-GFP fusion is also imported by isolated pea chloroplasts. The N-terminal portion of the cytochrome P450 protein ent-kaurene oxidase (AtKO1) directs GFP to chloroplasts in tobacco leaf transient assays. Chloroplast import assays with 35S-labelled AtKO1 protein show that it is targeted to the outer face of the chloroplast envelope. The leader sequences of the two ent-kaurenoic acid oxidases (AtKAO1 and AtKAO2) from Arabidopsis direct GFP to the endoplasmic reticulum. These data suggest that the AtKO1 protein links the plastid- and endoplasmic reticulum-located steps of the gibberellin biosynthesis pathway by association with the outer envelope of the plastid.
authors.affiliation: CSIRO Plant Industry, GPO Box 1600, ACT 2601, Australia. chrish@pi.csiro.au
authors.forename: C A
authors.initials: CA
authors.lastname: Helliwell
authors.forename: J A
authors.initials: JA
authors.lastname: Sullivan
authors.forename: R M
authors.initials: RM
authors.lastname: Mould
authors.forename: J C
authors.initials: JC
authors.lastname: Gray
authors.forename: W J
authors.initials: WJ
authors.lastname: Peacock
authors.forename: E S
authors.initials: ES
authors.lastname: Dennis
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D002736:Chloroplasts / Q000201:enzymology; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D017930:Genes, Reporter; D005875:Gibberellins / Q000096:biosynthesis*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D018532:Pisum sativum / Q000201:enzymology; D010957:Plasmids; D018087:Plastids / Q000201:enzymology*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D013820:Thermolysin / Q000494:pharmacology
chemical_list: D005875:Gibberellins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C066398:ent-kaurene oxidase; D013820:Thermolysin