Plants with increased expression of ent-kaurene oxidase are resistant to chemical inhibitors of this gibberellin biosynthesis enzyme.
The gibberellin (GA) biosynthetic pathway includes the three-step oxidation of ent-kaurene to ent-kaurenoic acid, catalyzed by the enzyme ent-kaurene oxidase (KO). Arabidopsis plants overexpressing the KO cDNA under the control of the cauliflower mosaic virus 35S promoter, with or without a translational fusion to a modified green fluorescent protein (GFP), are very similar to wild-type (WT) plants under normal growth conditions. In contrast, when WT and 35S:KO (or 35S:KO-GFP) seeds, seedlings or pollen tubes are grown in the presence of chemical inhibitors of KO, such as paclobutrazol and uniconazole, plants with increased KO expression are partially resistant to the effects of these inhibitors. In combination with the observation that decreased KO levels increase the sensitivity to KO inhibitors, the 35S:KO phenotypes demonstrate that the modification of KO enzyme levels could be used to create transgenic crop plants with altered KO inhibitor response. These results also suggest that the KO gene could be used as a selectable marker for plant regeneration based on resistance to KO inhibitors. Finally, the observation that pollen tubes expressing 35S:KO or 35S:KO-GFP have decreased sensitivity to KO inhibitors provides further evidence for a physiological role for GAs in pollen tube elongation.
Swain
Stephen M
SM
CSIRO Plant Industry, 585 River Ave, Merbein, Victoria 3505, Australia. Steve.Swain@csiro.au
Singh
Davinder P
DP
Helliwell
Chris A
CA
Poole
Andrew T
AT
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D017796:Caulimovirus / Q000235:genetics; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000187:drug effects; D005875:Gibberellins / Q000096:biosynthesis* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D010105:Oxygenases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011058:Pollen / Q000187:drug effects / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000502:physiology; D012639:Seeds / Q000502:physiology; D014230:Triazoles / Q000494:pharmacology
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D005875:Gibberellins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014230:Triazoles; D049452:Green Fluorescent Proteins; C053370:paclobutrazol; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C066398:ent-kaurene oxidase; C092705:uniconazole