Os06g0569500

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Annotated Information

Function

Gibberellins (GAs) are a group of diterpene-type plant hormones biosynthesized froment-kaurene via ent- kaurenoic acid. GAs are ubiquitously present in seed plants. The GA signal is perceived and transduced by the GID1 GA receptor/DELLA repressor pathway.All higher plants contain an ent-kaurene oxidase (KO), as such a cytochrome P450 (CYP) 701 family member is required for gibberellin (GA) phytohormone biosynthesis. While gene expansion and functional diversification of GA-biosynthesis-derived diterpene synthases into more specialized metabolism has been demonstrated, no functionally divergent KO/CYP701 homologs have been previously identified. Rice ( Oryza sativa) contains five CYP701A subfamily members in its genome,despite the fact that only one (OsKO2/CYP701A6) is required for GA biosynthesis .Therefore,The Rice dwarf virus (RDV), a member of the genus Phytoreovirus,causes dwarfed growth phenotypes in infected rice ( Oryza sativa) plants. The outer capsid protein P2 is essential during RDV infection of insects and thus influences transmission of RDV by the insect vector.P2 of RDV interacts with ent-kaurene oxidases, which play a key role in the biosynthesis of plant growth hormones gibberellins, in infected plants. the P2 protein of RDV interferes with the function of a cellular factor, through direct physical interactions, that is important for the biosynthesis of a growth hormone leading to symptom expression.P2 may provide a novel tool to investigate the regulation of GA metabolism for plant growth and development.GAs are biosyn-thesized from geranylgranyl diphosph ate, which is converted to ent-kaurene by 2 terpene syntheses, ent-copalyl diphosphate synthase, and ent-kaurene synthase, in plants.Then ent-kaurene is converted to GA12 by two cytochrome P450 enzymes, ent-kaurene oxidase (KO) and ent-kaurenoic acid oxidase (KAO). KO locates in the outer membrane of the plastid, and KAO locates in the endoplasmic reticulum.

=Expression

The biosynthetic pathway of GA.(from reference )

GA biosynthesis.(from reference )

Degradation of active C19-gibberellins (GAs) by dioxygenases through 2β-hydroxylation yields inactive GA products.We identified two genes in Arabidopsis (AtGA2ox7 and AtGA2ox8),using an activation-tagging mutant screen, that encode2β-hydroxylases.GA levels in both activation-tagged lines were reduced significantly, and the lines displayed dwarf phenotypes typical of mutants with a GA deficiency.Double loss-of-function Atga2ox7 Atga2ox8 mutants had twofold to fourfold higher levels of active GAs and displayed phenotypes associated with excess GAs, such as early bolting in short days,resistance to the GA biosynthesis inhibitor ancymidol, and decreased mRNA levels of AtGA20ox1,a gene in the GA biosynthetic pathway.The GA biosynthetic pathway can be classified into three stages. In the first stage, geranylgeranyl diphosphate is cyclized to ent-kaurene by copalyl diphosphate synthase and ent-kaurene synthase. In the second stage,ent-kaurene is oxidized by ent-kaurene oxidase to ent-kaurenoic acid, which in turn is oxidized by ent-kaurenoic acid oxidase in three steps to GA12.The bioactive GAs (GA1and GA4) are synthesized through a series of oxidation reactions of ent-kaurene by two types of oxidases. Both ent-kaurene oxidase and ent-kaurenoic acid oxidase are cytochrome P450 monoo xygenases that success ively convert ent-kaurene to GA12.GA12 is further converted tobioactive GA s by two 2-oxoglutarate-dependent dioxygenases, GA 20-oxidase and GA3-oxidase.GA 2-oxidase is another member of the 2-oxoglutarate-dependent dioxygenase family and is responsible for GA inactivation.The ring contraction catalyzed by the cytochrome P450 (CYP) ent-kaurenoic acid oxidase (KAO) is then the committed step in GA-specific biosynthesis.OsKO2 exhibits KO activity, OsKOL 4 does not, instead catalyzing C3a hydroxylation of ent-sandaracopimaradiene and ent-cassadiene, as well as ent-kaurene .

Evolution

Phenotypic Characterization of the gdd1 Mutant.(from reference )

Map-Based Cloning of GDD1 and Complementation Test.(from reference)

A rice mutant with greatly decreased height was isolated from a transgene line after Agrobacterium tumifaciens–mediated T-DNA insertion. The mutant, designated gibberellin-deficient dwarf1(gdd1), retained a stable phenotype and showed segregation of the b-glucuronidase (GUS) gene with the T-DNA insertions until T2 progeny, suggesting that the phenotype was independent of the T-DNA insertion, the mutant with neither the T-DNA insertion nor GUS fragment from the T2 progeny was used for analysis the function of GDD1 .To understand the molecular mechanism responsible for the gdd1 phenotype, we used a map-based cloning approach to isolate GDD1. All F1 progeny showed a height phenotype similar to that of the wild type. Tests of heterozygotes with F2 progeny yielded a segregation of 401 normal and 144 dwarf plants (x2[3:1] = 0.59 < x20.05= 3.84; P > 0.05), indicating that the dwarf phenotype of the gdd1 mutant is caused by a recessive mutation in a single nuclear gene.The GA7 gene encodes the enzyme ent-kaurene synthetase A, which catalyzes the conversion of GGPP to CPP. Subcellular localization of the GA1 protein was studied using 35S-labeled GA1 protein and isolated pea chloroplasts. The results showed that the GAl protein is imported into and processed in pea chloroplasts in vitro.DNA sequences of GA7 genomic DNA and cDNA were obtained using the dideoxy method with Sequenase version 2.0 T7 DNA polymerase (U.S.Biochemical Corp.)and both single and double-stranded DNA templates.The 1.4-kb Hindlll DNA in the ga7-9 mutant was amplified by PCR and reamplified by asymmetric PCR, and the single-stranded DNA templates were sequenced directly. The 1.4-kb DNA fragments spanning intron 12 to exon 15 were amplified from genomic DNA isolated from ga7-7 and ga7-4 by PCR. These PCR-amplified DNA products were cloned into the Smal site of the pBluescript SK+ vector, and DNA sequences were obtained by using double-stranded DNA templates isolated from severa1 independent clones.

Labs working on this gene

Department of Biochemistry, Okayama University of Science, Okayama 700–0005, Japan National Institute for Basic B iology, O kazaki444–8585, Japan School of Life Science,Grad uate University for Advanced Studies, O kazaki 444–8585, Japan Department of Botany, Box 91000, Duke University, Durham, North Carolina 27708-1000 Frontier Research Program, The lnstitute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan Research Center for Molecular and Developmental Biology, Key Laboratory of Photosyn thesis and Environ mental Molecular Physiology, Institute of Botany , Chinese Academy of Sciences , Beijing 100093, China

References

1、Ken-ichiro Hayashi, Keisuke Horie, Yu ji Hiwatashi et al.（2012）Endogenous Diterpenes Derived from ent-Kaurene, a Common Gibberellin Precursor, Regulate Protonema Diff erentiation of the Moss Physcomitrella patens1[W][OA]. Plant Physiology 153:1085-1097.

2、Qiang Wang, Matthew L . Hillwig, Yisheng Wu et al.（2012）CYP701A8: A Rice ent-Kaurene Oxidase P aralog Diverted to More Specialized Diterpenoid Metabolism1[W][OA]. Plant Physiology 158:1418-1425.

3、Shifeng Zhu , Feng Gao, Xue song Cao et al.(2005)The Rice Dwarf Virus P2 Protein Interacts with ent-Kaurene Oxidases in Vivo, Leading to Reduced Biosynthesis of Gibberellins and Rice Dwarf Symptoms1.Plant Physiology 139:1935-1945.

4、Juan Li,Jiafu Jiang,Qian Qian et al.(2011)Mutation of Rice BC12/GDD1, Which Encodes a Kinesin-Like Protein That Binds to a GA Biosynthesis Gene Promoter, Leads to Dwarfism with Impaired Cell Elongation.The Plant Cell 23:628-640.

5、Fritz M. Schomburg,Colleen M. Bizzell,Dong Ju Lee et ai.(2003)Overexpression of a Novel Class of Gibberellin 2-Oxidases Decreases Gibberellin Levels and Creates Dwarf Plants.The Plant Cell 15:151-163.

6、Tai-ping Sun,Yuji Kamiya.(1994)The Arabidopsis GAl Locus Encodes the Cyclase ent-Kaurene Synthetase A of Gibberellin Biosynthesis.The Plant Cell 6:1509-1518.