Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1998 Nov;118(3):773-81.
doi: 10.1104/pp.118.3.773.

Overexpression of 20-oxidase Confers a Gibberellin-Overproduction Phenotype in Arabidopsis

Affiliations
Free PMC article

Overexpression of 20-oxidase Confers a Gibberellin-Overproduction Phenotype in Arabidopsis

S Huang et al. Plant Physiol. .
Free PMC article

Abstract

In the gibberellin (GA) biosynthesis pathway, 20-oxidase catalyzes the oxidation and elimination of carbon-20 to give rise to C19-GAs. All bioactive GAs are C19-GAs. We have overexpressed a cDNA encoding 20-oxidase isolated from Arabidopsis seedlings in transgenic Arabidopsis plants. These transgenic plants display a phenotype that may be attributed to the overproduction of GA. The phenotype includes a longer hypocotyl, lighter-green leaves, increased stem elongation, earlier flowering, and decreased seed dormancy. However, the fertility of the transgenic plants is not affected. Increased levels of endogenous GA1, GA9, and GA20 were detected in seedlings of the transgenic line examined. GA4, which is thought to be the predominantly active GA in Arabidopsis, was not present at increased levels in this line. These results suggest that the overexpression of this 20-oxidase increases the levels of some endogenous GAs in transgenic seedlings, which causes the GA-overproduction phenotype.

Figures

Figure 1
Figure 1
DNA and RNA gel-blot analysis of 20-oxidase-overexpressing plants. A, DNA gel blot containing SpeI digests of genomic DNA (5 μg per lane) isolated from transgenic lines 25-1, 25-2, 25-3, 25-24, and a nontransgenic plant was hybridized with a 20-oxidase cDNA probe. The arrow marks a lower common band that is probably the endogenous 20-oxidase gene. B, RNA gel blot containing total seedling RNA (20 μg per lane) isolated from transgenic lines 25-1, 25-2, 25-3, 25-24, and a nontransgenic plant was hybridized with a 20-oxidase cDNA probe. On the bottom is an ethidium bromide stain of an agarose gel that was loaded with the RNA (1 μg per lane) used in the gel blot.
Figure 2
Figure 2
Promoted growth of 20-oxidase-overexpressing plants. The pictures compare the growth of transgenic (right) and wild-type (left) plants at 1 week (A), 3 weeks (B), 3.5 weeks (C), and 4 weeks of age (D). The plants shown are from the T3 generation of transgenic line 25-2. The transgenic plants are homozygous for the transgene and the wild-type plants are their nontransgenic siblings.
Figure 3
Figure 3
Germination efficiency comparison of freshly collected transgenic line 25-2 T4 and wild-type seeds. Germination efficiencies of seeds collected from the T3 generation of transgenic plants (+) and wild- type (−) plants are shown. Seeds were plated on medium for germination at 1 (⋄), 2 (▵), 3 (□), 4 (○), and 7 (×) weeks after harvesting. Transgenic plants are indicated by solid lines and wild-type plants are indicated by dashed lines.
Figure 4
Figure 4
Proposed three endogenous GA 20-oxidations in Arabidopsis. Different derivatives of C20-GAs can be oxidized by endogenous 20-oxidases to produce C19-GAs. The early 13-hydroxylation pathway leads to GA20; the non-3,13-hydroxylation pathway leads to GA9; and the early 3-hydroxylation pathway leads to GA4. GA9 can be 13-hydroxylated and 3β-hydroxylated to give GA20 and GA4. GA4 can be 13-hydroxylated and GA20 can be 3β-hydroxylated to give to GA1.
Figure 5
Figure 5
Endogenous GA levels in line 25-2 T4 and wild-type seedlings. Endogenous GA1, GA4, GA9, and GA20 levels in 7-d-old seedling were measured by GC-MS after GA extraction. The amounts are indicated by nanograms of GA in 1 g of seedlings (fresh weight).

Similar articles

See all similar articles

Cited by 60 articles

See all "Cited by" articles

Substances

LinkOut - more resources

Feedback