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Mitchum MG Yamaguchi S Hanada A Kuwahara A Yoshioka Y Kato T Tabata S Kamiya Y Sun TP 《The Plant journal : for cell and molecular biology》2006,45(5):804-818
Gibberellin (GA) 3-oxidase, a class of 2-oxoglutarate-dependent dioxygenases, catalyzes the conversion of precursor GAs to their bioactive forms, thereby playing a direct role in determining the levels of bioactive GAs in plants. Gibberellin 3-oxidase in Arabidopsis is encoded by a multigene family consisting of at least four members, designated AtGA3ox1 to AtGA3ox4. It has yet to be investigated how each AtGA3ox gene contributes to optimizing bioactive GA levels during growth and development. Using quantitative real-time PCR analysis, we have shown that each AtGA3ox gene exhibits a unique organ-specific expression pattern, suggesting distinct developmental roles played by individual AtGA3ox members. To investigate the sites of synthesis of bioactive GA in plants, we generated transgenic Arabidopsis that carried AtGA3ox1-GUS and AtGA3ox2-GUS fusions. Comparisons of the GUS staining patterns of these plants with that of AtCPS-GUS from previous studies revealed the possible physical separation of the early and late stages of the GA pathway in roots. Phenotypic characterization and quantitative analysis of the endogenous GA content of ga3ox1 and ga3ox2 single and ga3ox1/ga3ox2 double mutants revealed distinct as well as overlapping roles of AtGA3ox1 and AtGA3ox2 in Arabidopsis development. Our results show that AtGA3ox1 and AtGA3ox2 are responsible for the synthesis of bioactive GAs during vegetative growth, but that they are dispensable for reproductive development. The stage-specific severe GA-deficient phenotypes of the ga3ox1/ga3ox2 mutant suggest that AtGA3ox3 and AtGA3ox4 are tightly regulated by developmental cues; AtGA3ox3 and AtGA3ox4 are not upregulated to compensate for GA deficiency during vegetative growth of the double mutant. 相似文献
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Gibberellin (GA) 2-oxidases play an important role in the GA catabolic pathway through 2β-hydroxylation. There are two classes of GA2oxs, i.e., a larger class of C19-GA2oxs and a smaller class of C20-GA2oxs. In this study, the gene encoding a GA 2-oxidase of rice, Oryza sativa GA 2-oxidase 5 (OsGA2ox5), was cloned and characterized. BLASTP analysis showed that OsGA2ox5 belongs to the C20-GA2oxs subfamily, a subfamily of GA2oxs acting on C20-GAs (GA12, GA53). Subcellular localization of OsGA2ox5-YFP in transiently transformed onion epidermal cells revealed the presence of this protein in both of the nucleus and cytoplasm. Real-time PCR analysis, along with GUS staining, revealed that OsGA2ox5 is expressed in the roots, culms, leaves, sheaths and panicles of rice. Rice plants overexpressing OsGA2ox5 exhibited dominant dwarf and GA-deficient phenotypes, with shorter stems and later development of reproductive organs than the wild type. The dwarfism phenotype was partially rescued by the application of exogenous GA3 at a concentration of 10 µM. Ectopic expression of OsGA2ox5 cDNA in Arabidopsis resulted in a similar phenotype. Real-time PCR assays revealed that both GA synthesis-related genes and GA signaling genes were expressed at higher levels in transgenic rice plants than in wild-type rice; OsGA3ox1, which encodes a key enzyme in the last step of the bioactive GAs synthesis pathway, was highly expressed in transgenic rice. The roots of OsGA2ox5-ox plants exhibited increased starch granule accumulation and gravity responses, revealing a role for GA in root starch granule development and gravity responses. Furthermore, rice and Arabidopsis plants overexpressing OsGA2ox5 were more resistant to high-salinity stress than wild-type plants. These results suggest that OsGA2ox5 plays important roles in GAs homeostasis, development, gravity responses and stress tolerance in rice. 相似文献
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The endogenous gibberellins (GAs) from shoots of the GA-insensitive mutant,gai, ofArabidopsis thaliana were analyzed and compared with the GAs from the Landsberg erecta (Ler) line. Twenty GAs were identified in Ler plants by
full-scan gas chromatography-mass spectrometry (GC-MS) and Kovats retention indices (KRI's). These GAs are members of the
early-13-hydroxylation pathway (GA53, GA44, GA19, GA17, GA20, GA1, GA29, and GA8), the non-3,13-hydroxylation pathway (GA12, GA15, GA24, GA25, GA9, and GA51), and the early-3-hydroxylation pathway (GA37, GA27, GA36, GA13, GA4, and GA34). The same GAs, except GA53, GA44, GA37, and GA29 were detected in thegai mutant by the same methods. In addition, extracts fromgai plants contained GA41 and GA71. Both lines also contained several unknown GAs. In Ler plants these were mainly hydroxy-GA12 derivatives, whereas in thegai mutant hydroxy-GA24, hydroxy-GA25, and hydroxy-GA9 compounds were detected. Quantification of seven GAs by GC-selected ion monitoring (SIM), using internal standards, and comparisons
of the ion intensities in the SIM chromatograms of the other thirteen GAs, demonstrated that thegai mutant had reduced levels of all C20-dicarboxylic acids (GA53, GA44, GA19, GA12, GA15, GA24, GA37, GA27, and GA36). In contrast,gai plants had increased levels of C20-tricarboxylic acid GAs (GA17, GA25, and GA41) and of all C19-GAs (GA20, GA1, GA8, GA9, GA51, GA4, GA34, and GA71) except GA29. The 3β-hydroxylated GAs, GA1 and GA4, and their respective 2β-hydroxylated derivatives, GA8 and GA34, were the most abundant GAs found in shoots of thegai mutant. Thus, thegai mutation inArabidopsis results in a phenotype that resembles GA-deficient mutants, is insensitive to both applied and endogenous GAs, and contains
low levels of C20-dicarboxylic acid GAs and high levels of C19-GAs. This indicates that theGAI gene controls a step beyond the synthesis of an active GA. Thegai mutant is presumably a GA-receptor mutant or a mutant with a block in the transduction pathway between the receptor and stem
elongation.
We thank Dr. L.N. Mander, Australian National University, Canberra, for providing [2H]gibberellins, Dr. B.O. Phinney, University of California, Los Angeles, USA for [13C]GA8, and Dr. D.A. Gage, MSU-NIH Mass Spectrometry Facility (grant No. DRR00480), for advice with mass spectrometry. This work
was supported by a fellowship from the Spanish Ministry of Agriculture (I.N.I.A.) to M.T., by the U.S. Department of Energy
under Contract DE-ACO2-76ERO-1338, and by U.S. Department of Agriculture grant No. 88-37261-3434 to J.A.D.Z. 相似文献
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Although salt stress mainly disturbs plant root growth by affecting the biosynthesis and signaling of phytohormones, such as gibberellin (GA) and auxin, the exact mechanisms of the crosstalk between these two hormones remain to be clarified. Indole-3-acetic acid (IAA) is a biologically active auxin molecule. In this study, we investigated the role of Arabidopsis GA20-oxidase 2 (GA20ox2), a final rate-limiting enzyme of active GA biosynthesis, in IAA-directed root growth under NaCl stress. Under the NaCl treatment, seedlings of a loss-of-function ga20ox2-1 mutant exhibited primary root and root hair elongation, altered GA4 accumulation, and decreased root Na+ contents compared with the wild-type, transgenic GA20ox2-complementing, and GA20ox2-overexpression plant lines. Concurrently, ga20ox2-1 alleviated the tissue-specific inhibition of NaCl on IAA generation by YUCCAs, IAA transport by PIN1 and PIN2, and IAA accumulation in roots, thereby explaining how NaCl increased GA20ox2 expression in shoots but disrupted primary root and root hair growth in wild-type seedlings. In addition, a loss-of-function pin2 mutant impeded GA20ox2 expression, indicating that GA20ox2 function requires PIN2 activity. Thus, the activation of GA20ox2 retards IAA-directed primary root and root hair growth in response to NaCl stress. 相似文献
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Rafal Archacki Daniel Buszewicz Tomasz J. Sarnowski Elzbieta Sarnowska Anna T. Rolicka Takayuki Tohge Alisdair R. Fernie Yusuke Jikumaru Maciej Kotlinski Roksana Iwanicka-Nowicka Katarzyna Kalisiak Jacek Patryn Joanna Halibart-Puzio Yuji Kamiya Seth J. Davis Marta K. Koblowska Andrzej Jerzmanowski 《PloS one》2013,8(3)
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The semi-dominant gai mutation of arabidopsis confers a dark-green dwarf phenotype resembling that of gibberellin (GA)-deficient mutants. In contrast to GA-deficient mutants, gai mutants do not respond to GA treatments and accumulate higher levels of bioactive GAs than are found in wild-type controls. The gai mutation thus alters the responses of plant cells to GA, indicating that the GAI (wild-type) gene product is involved in GA reception and/or signal transduction. Here we describe the isolation and preliminary characterization of a mutation, gas1-1, which is not linked to gai and which partially suppresses the effect of the gai mutation. Double mutant, gai gas1-1, homozygotes are less severely dwarfed and lighter green than gai GAS1 controls. However, comparisons of the effects of treatments with exogenous GA demonstrate that gas1-1 does not increase the GA responsiveness of the gai mutant. Thus the gas1-1 mutation appears to reduce the GA-dependency of plant growth, and identifies a gene (GAS1) whose product is a candidate GA signal-transduction component.Abbreviations GA
gibberellin
- GA3
gibberellic acid
We thank Maarten Koornneef (Wageningen Agricultural University, The Netherlands) for providing mutant seed stocks; Mark Aarts and Bernard Mulligan (University of Nottingham, UK) for performing the -irradiation. This work was made possible by AFRC/BBSRC PMB Grants PG208/520 and PG208/0600, and by a grant from the Gatsby Charitable Foundation. P.C. was supported by a Human Capital and Mobility Fellowship from the EC. 相似文献
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Gibberellins (GAs) are phytohormones controlling major aspects of plant growth and development. Although previous studies suggested the existence of a transport of GAs in plants, the nature and properties associated with this transport were unknown. We recently showed through micrografting and biochemical approaches that the GA12 precursor is the chemical form of GA undergoing long-distance transport across plant organs in Arabidopsis. Endogenous GA12 moves through the plant vascular system from production sites to recipient tissues, in which GA12 can be converted to bioactive forms to support growth via the activation of GA-dependent processes. GAs are also essential to promote seed germination; hence GA biosynthesis mutants do not germinate without exogenous GA treatment. Our results suggest that endogenous GAs are not (or not sufficiently) transmitted to the offspring to successfully complete the germination under permissive conditions. 相似文献
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Putri Prasetyaningrum Lorenzo Mariotti Maria Cristina Valeri Giacomo Novi Stijn Dhondt Dirk Inz Pierdomenico Perata Hans van Veen 《Plant physiology》2021,185(1):228
Optimal plant growth performance requires that the presence and action of growth signals, such as gibberellins (GAs), are coordinated with the availability of photo-assimilates. Here, we studied the links between GA biosynthesis and carbon availability, and the subsequent effects on growth. We established that carbon availability, light and dark cues, and the circadian clock ensure the timing and magnitude of GA biosynthesis and that disruption of these factors results in reduced GA levels and expression of downstream genes. Carbon-dependent nighttime induction of gibberellin 3-beta-dioxygenase 1 (GA3ox1) was severely hampered when preceded by reduced daytime light availability, leading specifically to reduced bioactive GA4 levels, and coinciding with a decline in leaf expansion rate during the night. We attributed this decline in leaf expansion mostly to reduced photo-assimilates. However, plants in which GA limitation was alleviated had significantly improved leaf expansion, demonstrating the relevance of GAs in growth control under varying carbon availability. Carbon-dependent expression of upstream GA biosynthesis genes (Kaurene synthase and gibberellin 20 oxidase 1, GA20ox1) was not translated into metabolite changes within this short timeframe. We propose a model in which the extent of nighttime biosynthesis of bioactive GA4 by GA3ox1 is determined by nighttime consumption of starch reserves, thus providing day-to-day adjustments of GA responses.GA-sugar matching occurs specifically at night and determines day to day adjustment of GA levels and subsequent growth. 相似文献
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Sabine Albermann Tino Elter Andreas Teubner Wolfgang Krischke Thomas Hirth Bettina Tudzynski 《Applied microbiology and biotechnology》2013,97(17):7779-7790
The rice pathogen Fusarium fujikuroi is known for producing a wide range of secondary metabolites such as pigments, mycotoxins, and a group of phytohormones, the gibberellic acids (GAs). Bioactive forms of these diterpenes are responsible for hyperelongation of rice stems, yellowish chlorotic leaves, and reduced grain formation during the bakanae disease leading to severely decreased crop yields. GAs are also successfully applied in agriculture and horticulture as plant growth regulators to enhance crop yields, fruit size, and to induce earlier flowering. In this study, six F. fujikuroi wild-type and mutant strains differing in GA yields and the spectrum of produced GAs were cultivated in high-quality lab fermenters for optimal temperature and pH control and compared regarding their growth, GA production, and GA gene expression levels. Comparative analysis of the six strains revealed that strain 6314/ΔDES/ΔPPT1, holding mutations in two GA biosynthetic genes and an additional deletion of the 4'-phosphopantetheinyl transferase gene PPT1, exhibits the highest total GA amount. Expression studies of two GA biosynthesis genes, CPS/KS and DES, showed a constantly high expression level for both genes under production conditions (nitrogen limitation) in all strains. By cultivating these genetically engineered mutant strains, we were able to produce not only mixtures of different bioactive GAs (GA3, GA4, and GA7) but also pure GA4 or GA7. In addition, we show that the GA yields are not only determined by different production rates, but also by different decomposition rates of the end products GA3, GA4, and GA7 explaining the varying GA levels of genetically almost identical mutant strains. 相似文献
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ELONGATED UPPERMOST INTERNODE encodes a cytochrome P450 monooxygenase that epoxidizes gibberellins in a novel deactivation reaction in rice 总被引:11,自引:0,他引:11
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Zhu Y Nomura T Xu Y Zhang Y Peng Y Mao B Hanada A Zhou H Wang R Li P Zhu X Mander LN Kamiya Y Yamaguchi S He Z 《The Plant cell》2006,18(2):442-456
The recessive tall rice (Oryza sativa) mutant elongated uppermost internode (eui) is morphologically normal until its final internode elongates drastically at the heading stage. The stage-specific developmental effect of the eui mutation has been used in the breeding of hybrid rice to improve the performance of heading in male sterile cultivars. We found that the eui mutant accumulated exceptionally large amounts of biologically active gibberellins (GAs) in the uppermost internode. Map-based cloning revealed that the Eui gene encodes a previously uncharacterized cytochrome P450 monooxygenase, CYP714D1. Using heterologous expression in yeast, we found that EUI catalyzed 16α,17-epoxidation of non-13-hydroxylated GAs. Consistent with the tall and dwarfed phenotypes of the eui mutant and Eui-overexpressing transgenic plants, respectively, 16α,17-epoxidation reduced the biological activity of GA4 in rice, demonstrating that EUI functions as a GA-deactivating enzyme. Expression of Eui appeared tightly regulated during plant development, in agreement with the stage-specific eui phenotypes. These results indicate the existence of an unrecognized pathway for GA deactivation by EUI during the growth of wild-type internodes. The identification of Eui as a GA catabolism gene provides additional evidence that the GA metabolism pathway is a useful target for increasing the agronomic value of crops. 相似文献
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Zheng Xiao Ruipeng Fu Jiyuan Li Zhengqi Fan Hengfu Yin 《Plant Molecular Biology Reporter》2016,34(1):182-191
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cDNA
corresponding to the GA4 gene of
Arabidopsis thaliana L. (Heynh.) was
expressed in Escherichia coli, from which cell lysates
converted [14C]gibberellin (GA)9 and
[14C]GA20 to radiolabeled GA4 and
GA1, respectively, thereby confirming that
GA4 encodes a GA 3β-hydroxylase. GA9 was
the preferred substrate, with a Michaelis value of 1 μm
compared with 15 μm for GA20. Hydroxylation
of these GAs was regiospecific, with no indication of
2β-hydroxylation or 2,3-desaturation. The capacity of the recombinant
enzyme to hydroxylate a range of other GA substrates was investigated.
In general, the preferred substrates contained a polar bridge between
C-4 and C-10, and 13-deoxy GAs were preferred to their 13-hydroxylated
analogs. Therefore, no activity was detected using
GA12-aldehyde, GA12, GA19,
GA25, GA53, or GA44 as the open
lactone (20-hydroxy-GA53), whereas GA15,
GA24, and GA44 were hydroxylated to
GA37, GA36, and GA38, respectively.
The open lactone of GA15 (20-hydroxy-GA12) was
hydroxylated but less efficiently than GA15. In contrast to
the free acid, GA25 19,20-anhydride was 3β-hydroxylated
to give GA13. 2,3-Didehydro-GA9 and
GA5 were converted by recombinant GA4 to the corresponding
epoxides 2,3-oxido-GA9 and GA6.Dwarf mutants with reduced biosynthesis of the GA plant hormones
have been valuable tools in studies of the function of these compounds
(Ross, 1994). In Arabidopsis thaliana, mutations
at six loci (GA1-GA6) that result in reduced GA
biosynthesis have been identified (Koorneef and van der Veen, 1980;
Sponsel et al., 1997), and three of these loci have recently been
cloned. The GA1 locus was isolated by genomic subtraction
(Sun et al., 1992) and shown by heterologous expression in
Escherichia coli to encode the enzyme that cyclizes
geranylgeranyl diphosphate to copalyl diphosphate (Sun and Kamiya,
1994). This enzyme was formerly referred to as ent-kaurene
synthase A but has been renamed copalyl diphosphate synthase
(Hedden and Kamiya, 1997; MacMillan, 1997). The GA5
locus was shown to correspond to one of the GA 20-oxidase genes (Xu et
al., 1995), the products of which catalyze the conversion of
GA12 to GA9 and
GA53 to GA20 (Phillips et
al., 1995; Xu et al., 1995). GA 20-oxidases are
2-oxoglutarate-dependent dioxygenases that are encoded by small
multigene families, members of which are differentially expressed in
plant tissues (Phillips et al., 1995; Garcia-Martinez et al., 1997).The GA4 locus was isolated by T-DNA tagging and, on the
basis of the derived amino acid sequence, was also shown to encode a
dioxygenase (Chiang et al., 1995). Several lines of evidence indicate
that the GA4 gene encodes a GA 3β-hydroxylase. Shoots of a
ga4 mutant, all alleles of which are semidwarf, contained
reduced concentrations of the 3β-hydroxy GAs
GA1, GA4, and
GA8 compared with the Landsberg erecta
wild type, whereas levels of immediate precursors to these GAs were
elevated (Talon et al., 1990). Furthermore, metabolism of
[13C]GA20 to
[13C]GA1 was
substantially less in the mutant than in the wild type (Kobayashi et
al., 1994). In the present paper we confirm by functional expression of
its cDNA in E. coli that GA4 encodes a GA
3β-hydroxylase. In addition, we determine the substrate specificity
of recombinant GA4 using a number of C20- and
C19-GAs and show by kinetic analysis that the enzyme
has a higher affinity for GA9 than for
GA20, which is consistent with the
non-13-hydroxylation pathway predominating in Arabidopsis (Talon et
al., 1990). 相似文献