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

Huang, Shihshieh; Raman, Anuradha; Ream, Joel E.; Fujiwara, Hideji; Cerny, R. Eric; Brown, Sherri M.

doi:10.1104/pp.118.3.773

Cited by 207 publications

(184 citation statements)

References 16 publications

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“…Wild-type seedlings accumulated the expected levels of both GA 4 and GA 1 (Huang et al, 1998). However, athb25-1D seedlings accumulated 1.4 times more GA 4 and showed a 3.2-fold increase in the level of GA 1 (Fig.…”

Section: Ga-dependent Phenotypes In Athb25-overexpressing Linesmentioning

confidence: 82%

“…In order to determine whether GA-dependent phenotypes exhibited by ATHB25-overexpressing lines are due to the overproduction of this hormone, as observed in lines overexpressing GA20OX1 (Huang et al, 1998), or due to the constitutive activation of the GA signaling pathway, as in spindly mutants (Jacobsen and Olszewski, 1993), the level of the endogenous bioactive GA was measured in 10-d-old seedlings. Wild-type seedlings accumulated the expected levels of both GA 4 and GA 1 (Huang et al, 1998).…”

Section: Ga-dependent Phenotypes In Athb25-overexpressing Linesmentioning

confidence: 99%

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ARABIDOPSIS THALIANA HOMEOBOX25 Uncovers a Role for Gibberellins in Seed Longevity

et al. 2013

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Seed longevity is crucial for agriculture and plant genetic diversity, but it is limited by cellular damage during storage. Seeds are protected against aging by cellular defenses and by structures such as the seed coat. We have screened an activation-tagging mutant collection of Arabidopsis (Arabidopsis thaliana) and selected four dominant mutants with improved seed longevity (isl1-1D to isl4-1D) under both natural and accelerated aging conditions. In the isl1-1D mutant, characterized in this work, overexpression of the transcription factor ARABIDOPSIS THALIANA HOMEOBOX25 (ATHB25; At5g65410) increases the expression of GIBBERELLIC ACID3-OXIDASE2, encoding a gibberellin (GA) biosynthetic enzyme, and the levels of GA 1 and GA 4 are higher (3.2-and 1.4-fold, respectively) in the mutant than in the wild type. The morphological and seed longevity phenotypes of the athb25-1D mutant were recapitulated in transgenic plants with moderate (4-to 6-fold) overexpression of ATHB25. Simultaneous knockdown of ATHB25, ATHB22, and ATHB31 expression decreases seed longevity, as does loss of ATHB25 and ATHB22 function in a double mutant line. Seeds from wild-type plants treated with GA and from a quintuple DELLA mutant (with constitutive GA signaling) are more tolerant to aging, providing additional evidence for a role of GA in seed longevity. A correlation was observed in several genotypes between seed longevity and mucilage formation at the seed surface, suggesting that GA may act by reinforcing the seed coat. This mechanism was supported by the observation of a maternal effect in reciprocal crosses between the wild type and the athb25-1D mutant.

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Section: Ga-dependent Phenotypes In Athb25-overexpressing Linesmentioning

confidence: 82%

Section: Ga-dependent Phenotypes In Athb25-overexpressing Linesmentioning

confidence: 99%

ARABIDOPSIS THALIANA HOMEOBOX25 Uncovers a Role for Gibberellins in Seed Longevity

et al. 2013

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“…Overexpression of JAW1, which is involved in the regulation of jasmonate biosynthesis (Palatnik et al, 2003;Schommer et al, 2008), leads to the enlargement of only the first rosette leaves, and these have a characteristic uneven shape. Leaf enlargement is also restricted to the first few rosette leaves in lines overexpressing GRF5 and BRI1, a brassinosteroid receptor (Wang et al, 2001;Horiguchi et al, 2005), whereas overexpression of GA20OX1, an enzyme involved in GA synthesis (Huang et al, 1998), yields enlarged young but not older leaves.…”

Section: Discussionmentioning

confidence: 99%

The Sink-Specific Plastidic Phosphate Transporter PHT4;2 Influences Starch Accumulation and Leaf Size in Arabidopsis

et al. 2011

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Nonphotosynthetic plastids are important sites for the biosynthesis of starch, fatty acids, and amino acids. The uptake and subsequent use of cytosolic ATP to fuel these and other anabolic processes would lead to the accumulation of inorganic phosphate (Pi) if not balanced by a Pi export activity. However, the identity of the transporter(s) responsible for Pi export is unclear. The plastid-localized Pi transporter PHT4;2 of Arabidopsis (Arabidopsis thaliana) is expressed in multiple sink organs but is nearly restricted to roots during vegetative growth. We identified and used pht4;2 null mutants to confirm that PHT4;2 contributes to Pi transport in isolated root plastids. Starch accumulation was limited in pht4;2 roots, which is consistent with the inhibition of starch synthesis by excess Pi as a result of a defect in Pi export. Reduced starch accumulation in leaves and altered expression patterns for starch synthesis genes and other plastid transporter genes suggest metabolic adaptation to the defect in roots. Moreover, pht4;2 rosettes, but not roots, were significantly larger than those of the wild type, with 40% greater leaf area and twice the biomass when plants were grown with a short (8-h) photoperiod. Increased cell proliferation accounted for the larger leaf size and biomass, as no changes were detected in mature cell size, specific leaf area, or relative photosynthetic electron transport activity. These data suggest novel signaling between roots and leaves that contributes to the regulation of leaf size.

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“…Accelerated growth as a response to ectopic GA20ox expression and increased levels of GA growth regulator have also been observed in Arabidopsis (Huang et al, 1998;Coles et al, 1999), potato (Solanum tuberosum; Carrera et al, 2000), and tobacco (Nicotiana tabacum; Vidal et al, 2001), implying that this enzyme has a limiting role in regulating the production of bioactive GAs. In contrast, when the genes coding for ent-copalyl diphosphate synthase and ent-kaurene synthase, which are involved in early stages of GA biosynthesis, are overexpressed in Arabidopsis, no significantly increased levels of bioactive GA are observed (Fleet et al, 2003).…”

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confidence: 96%

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

et al. 2004

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To broaden our understanding of gibberellin (GA) biosynthesis and the mechanism whereby GA homeostasis is maintained in plants, we have investigated the degree to which the enzyme GA 3-oxidase (GA3ox) limits the formation of bioactive GAs in elongating shoots of hybrid aspen (Populus tremula 3 Populus tremuloides). We describe the cloning of a hybrid aspen GA3ox and its functional characterization, which confirmed that it has 3b-hydroxylation activity and more efficiently converts GA 9 to GA 4 than GA 20 to GA 1 . To complement previous studies, in which transgenic GA 20-oxidase (GA20ox) overexpressers were found to produce 20-fold higher bioactive GA levels and subsequently grew faster than wild-type plants, we overexpressed an Arabidopsis GA3ox in hybrid aspen. The generated GA3ox overexpresser lines had increased 3b-hydroxylation activity but exhibited no major changes in morphology. The nearly unaltered growth pattern was associated with relatively small changes in GA 1 and GA 4 levels, although tissue-dependent differences were observed. The absence of increases in bioactive GA levels did not appear to be due to feedback or feed-forward regulation of dioxygenase transcripts, according to semiquantitative reverse transcription polymerase chain reaction analysis of PttGA20ox1, PttGA3ox1, and two putative PttGA2ox genes. We conclude that 20-oxidation is the limiting step, rather than 3b-hydroxylation, in the formation of GA 1 and GA 4 in elongating shoots of hybrid aspen, and that ectopic GA3ox expression alone cannot increase the flux toward bioactive GAs. Finally, several lines of evidence now suggest that GA 4 has a more pivotal role in the tree hybrid aspen than previously believed. Gibberellins (GAs) form a group of more than 130 tetracyclic diterpenes, some of which are biologically active and act as growth regulators in higher plants. Work on GA-deficient mutants has established that bioactive GAs play an important role in controlling diverse developmental processes such as seed germination, stem elongation, flowering, and fruit ripening (Davies, 1995). The GA biosynthetic pathway has been elucidated and its key components identified (for review, see Hedden and Phillips, 2000;Yamaguchi and Kamiya, 2000;Olszewski et al., 2002). The final steps in the pathway are catalyzed by the soluble 2-oxoglutarate-dependent dioxygenases GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox). The pathway branches at GA 12 , which can be 13-hydroxylated into GA 53 , marking the starting points for two parallel routes catalyzed by the above dioxygenases: the early nonhydroxylated and the 13-hydroxylated pathways forming the bioactive GAs, GA 4 and GA 1 , respectively. The multifunctional GA20ox removes a carbon by successive oxidation of GA 12 to GA 9 and GA 53 to GA 20 . However, the final interconversion into the bioactive GA 4 or GA 1 requires the action of the enzyme GA3ox. The deactivation of the bioactive species is catalyzed by GA2ox, which can also divert GA 9 and GA 20 away from the route toward...

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

Cited by 207 publications

References 16 publications

ARABIDOPSIS THALIANA HOMEOBOX25 Uncovers a Role for Gibberellins in Seed Longevity

ARABIDOPSIS THALIANA HOMEOBOX25 Uncovers a Role for Gibberellins in Seed Longevity

The Sink-Specific Plastidic Phosphate Transporter PHT4;2 Influences Starch Accumulation and Leaf Size in Arabidopsis

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

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