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Li J, Liang P, Gao L, Lu H, Dong Y, Zhang J. o-Nitrobenzyl-Based Caged exo-16,17-Dihydro-gibberellin A5-13-acetate for Photocontrolled Release of Plant Growth Regulators. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:16533-16541. [PMID: 37878916 DOI: 10.1021/acs.jafc.3c05259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
Caged plant growth regulators (caged PGRs) that release bioactive molecules under irradiation are critical in enhancing the efficacy and mitigating the negative environmental effects of PGRs. The synthetically derived plant growth inhibitor exo-16,17-dihydro-gibberellin A5-13-acetate (DHGA5) regulates the development and stress resilience of plants. We report here the conception of novel caged DHGA5 derivatives wherein the photoremovable protecting groups (PRPGs) serve not only to enable light-controlled release but also to protect the carboxyl group during chemical synthesis. Three o-nitrobenzyl-based caged DHGA5 derivatives with different substituents on the nitrobenzyl moiety were obtained and evaluated for their properties in vitro and in vivo. The photolysis half-life values of caged DHGA5 derivatives 7a, 7b, and 7c under a UV lamp were 15.6 h, 1.2 h, and 28.2 h, respectively. Experiments in vivo showed that 0.2 mM of the caged compounds significantly inhibited the growth of the model plant Arabidopsis thaliana and important crop rice in a precise photoactivated form.
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Affiliation(s)
- Jingmin Li
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Peibo Liang
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Linying Gao
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Huizhe Lu
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Yanhong Dong
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Jianjun Zhang
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
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Berli FJ, Alonso R, Pharis RP, Bottini R. Applied GA 5 , GA 4 , and GA 4/7 increase berry number per bunch, yield, and grape quality for winemaking in Vitis vinifera L. cv. Malbec. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2022; 102:2950-2959. [PMID: 34767265 DOI: 10.1002/jsfa.11635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 11/05/2021] [Accepted: 11/07/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND The gibberellins (GAs) GA5 (inhibitor of GA3 -oxidase), GA4 (biologically active), GA4/7 (commercially available mixture of Ga4 and GA7 ) prohexadione-calcium (ProCa, inhibitor of dioxygenases that render GAs bioactive, negative control), and GA3 (positive control) were applied to bunches of Vitis vinifera cv. Malbec. Different techniques, doses, and timings were used in a 3-year field experiment. In year 1, GA5 , ProCa, and GA3 were applied at 35, 20, and 0 days before veraison (DBV) by dipping bunches three times. In year 2, single applications of GA5 and GA3 , also by immersion, were tested at 60, 45, and 30 DBV. In year 3, applications at 60 and 30 DBV of GA5 , GA4 , and a mixture of GA4/7 were evaluated by dipping or spraying the bunches. RESULTS Vegetative growth, berry weight, and sugar content were unaffected by treatments. ProCa did not affect the yield with respect to water control, although it reduced the levels of phenolics in berry skins, an undesirable effect for winemaking. GA5 , in the dose range 5-50 mg L-1 , raised berry numbers, thereby augmenting bunch weight and skin phenolics at harvest, so increasing berry quality for winemaking. GA4 and GA4/7 produced similar benefits to GA5 , with similar doses. CONCLUSION The applications of GA5 , GA4 , and GA4/7 to developing grape berry bunches, in a range of concentrations and by dipping or spraying, increased berry numbers per bunch at harvest. The method can be used as a viticultural practice to improve the production and quality of wine grapes. © 2021 Society of Chemical Industry.
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Affiliation(s)
- Federico J Berli
- Grupo de Bioquímica Vegetal, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Cuyo, Chacras de Coria, Argentina
| | - Rodrigo Alonso
- Grupo de Bioquímica Vegetal, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Cuyo, Chacras de Coria, Argentina
| | - Richard P Pharis
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Rubén Bottini
- Instituto Argentino de Veterinaria, Ambiente y Salud, Universidad Juan Agustín Maza, Guaymallén, Argentina
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Tian H, He Y, Liu S, Yang Z, Wang J, Li J, Zhang J, Duan L, Li Z, Tan W. Improved synthetic route of exo-16,17-dihydro-gibberellin A5-13-acetate and the bioactivity of its derivatives towards Arabidopsis thaliana. PEST MANAGEMENT SCIENCE 2020; 76:807-817. [PMID: 31400044 DOI: 10.1002/ps.5584] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 07/05/2019] [Accepted: 07/26/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND The use of exo-16,17-dihydro-gibberellin A5-13-acetate (DHGA5 ) in agriculture has been limited by its low synthetic yield. This study was aimed at optimizing the synthetic route of DHGA5 , designing and synthesizing new derivatives with strong plant growth inhibitory activities. RESULTS Previous synthetic methods were replaced with a shorter, milder and faster reaction route with higher yield (76.3%) of DHGA5 . Based on this novel route, a series of new derivatives were designed and synthesized using DHGA5 as a lead compound and characterized and evaluated for biological activities in Arabidopsis thaliana. Among the 15 tested derivatives, compound 14j showed a lower medium inhibition concentration (IC50 , 73 μm) in Arabidopsis than that of DHGA5 (91 μm). Gibberellin deficient mutant assay further revealed that 14j had very different activities compared to DHGA5 as it specifically inhibits gibberellin biosynthetic pathways. In addition, 14j does not influence the interaction between gibberellin receptors (GID1) and the master growth repressor (RGA) based on yeast two-hybrid assay. CONCLUSION The optimized synthetic route provides a promising method for large-scale preparation of DHGA5 . Our biological assays indicate that 14j likely acts on gibberellin signaling elements other than GID1. These results indicate that novel plant growth regulators can be developed. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Hao Tian
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Yan He
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Shaojin Liu
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Zhikun Yang
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Jine Wang
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Jianmin Li
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Jianjun Zhang
- Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, PR China
| | - Liusheng Duan
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Zhaohu Li
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
| | - Weiming Tan
- Engineering Research Center of Plant Growth Regulator, Ministry of Education, Department of Agronomy, College of Agronomy and Biotechnology, China Agricultural University, Beijing, PR China
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Oh S, Strand DD, Kramer DM, Chen J, Montgomery BL. Transcriptome and phenotyping analyses support a role for chloroplast sigma factor 2 in red-light-dependent regulation of growth, stress, and photosynthesis. PLANT DIRECT 2018; 2:e00043. [PMID: 31245709 PMCID: PMC6508532 DOI: 10.1002/pld3.43] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 01/23/2018] [Accepted: 01/25/2018] [Indexed: 05/04/2023]
Abstract
Sigma factor (SIG) proteins contribute to promoter specificity of the plastid-encoded RNA polymerase during chloroplast genome transcription. All six members of the SIG family, that is, SIG1-SIG6, are nuclear-encoded proteins targeted to chloroplasts. Sigma factor 2 (SIG2) is a phytochrome-regulated protein important for stoichiometric control of the expression of plastid- and nuclear-encoded genes that impact plastid development and plant growth and development. Among SIG factors, SIG2 is required not only for transcription of chloroplast genes (i.e., anterograde signaling), but also impacts nuclear-encoded, photosynthesis-related, and light signaling-related genes (i.e., retrograde signaling) in response to plastid functional status. Although SIG2 is involved in photomorphogenesis in Arabidopsis, the molecular bases for its role in light signaling that impacts photomorphogenesis and aspects of photosynthesis have only recently begun to be investigated. Previously, we reported that SIG2 is necessary for phytochrome-mediated photomorphogenesis specifically under red (R) and far-red light, thereby suggesting a link between phytochromes and nuclear-encoded SIG2 in light signaling. To explore transcriptional roles of SIG2 in R-dependent growth and development, we performed RNA sequencing analysis to compare gene expression in sig2-2 mutant and Col-0 wild-type seedlings at two developmental stages (1- and 7-day). We identified a subset of misregulated genes involved in growth, hormonal cross talk, stress responses, and photosynthesis. To investigate the functional relevance of these gene expression analyses, we performed several comparative phenotyping tests. In these analyses, strong sig2 mutants showed insensitivity to bioactive GA 3, high intracellular levels of hydrogen peroxide (H2O2) indicative of a stress response, and specific defects in photosynthesis, including elevated levels of cyclic electron flow (CEF) and nonphotochemical quenching (NPQ). We demonstrated that SIG2 regulates a broader range of physiological responses at the molecular level than previously reported, with specific roles in red-light-mediated photomorphogenesis.
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Affiliation(s)
- Sookyung Oh
- Department of Energy – Plant Research LaboratoryMichigan State UniversityEast LansingMIUSA
| | - Deserah D. Strand
- Department of Energy – Plant Research LaboratoryMichigan State UniversityEast LansingMIUSA
- Present address:
Max‐Planck‐Institut für Molekulare PflanzenphysiologiePotsdam‐GolmGermany
| | - David M. Kramer
- Department of Energy – Plant Research LaboratoryMichigan State UniversityEast LansingMIUSA
- Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingMIUSA
| | - Jin Chen
- UK Medical Center MN 150University of Kentucky College of MedicineLexingtonKYUSA
| | - Beronda L. Montgomery
- Department of Energy – Plant Research LaboratoryMichigan State UniversityEast LansingMIUSA
- Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingMIUSA
- Department of Microbiology & Molecular GeneticsMichigan State UniversityEast LansingMIUSA
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Catalytic strategies of the non-heme iron dependent oxygenases and their roles in plant biology. Curr Opin Chem Biol 2016; 31:126-35. [PMID: 27015291 PMCID: PMC4879150 DOI: 10.1016/j.cbpa.2016.02.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 02/25/2016] [Accepted: 02/26/2016] [Indexed: 12/18/2022]
Abstract
Current evidence for iron-oxo reactive intermediates is reviewed. In crystallo intermediates detected in a native extradiol dioxygenase reaction. Carotenoid cleavage dioxygenases catalyse strigolactone biosynthesis. Identification of plant cysteine oxidases involved in the plant hypoxic response. Applications of enzyme manipulation to plant biology and agriculture are discussed.
Non-heme iron-dependent oxygenases catalyse the incorporation of O2 into a wide range of biological molecules and use diverse strategies to activate their substrates. Recent kinetic studies, including in crystallo, have provided experimental support for some of the intermediates used by different subclasses of this enzyme family. Plant non-heme iron-dependent oxygenases have diverse and important biological roles, including in growth signalling, stress responses and secondary metabolism. Recently identified roles include in strigolactone biosynthesis, O-demethylation in morphine biosynthesis and regulating the stability of hypoxia-responsive transcription factors. We discuss current structural and mechanistic understanding of plant non-heme iron oxygenases, and how their chemical/genetic manipulation could have agricultural benefit, for example, for improved yield, stress tolerance or herbicide development.
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Middleton AM, Úbeda-Tomás S, Griffiths J, Holman T, Hedden P, Thomas SG, Phillips AL, Holdsworth MJ, Bennett MJ, King JR, Owen MR. Mathematical modeling elucidates the role of transcriptional feedback in gibberellin signaling. Proc Natl Acad Sci U S A 2012; 109:7571-6. [PMID: 22523240 PMCID: PMC3358864 DOI: 10.1073/pnas.1113666109] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hormone gibberellin (GA) is a key regulator of plant growth. Many of the components of the gibberellin signal transduction [e.g., GIBBERELLIN INSENSITIVE DWARF 1 (GID1) and DELLA], biosynthesis [e.g., GA 20-oxidase (GA20ox) and GA3ox], and deactivation pathways have been identified. Gibberellin binds its receptor, GID1, to form a complex that mediates the degradation of DELLA proteins. In this way, gibberellin relieves DELLA-dependent growth repression. However, gibberellin regulates expression of GID1, GA20ox, and GA3ox, and there is also evidence that it regulates DELLA expression. In this paper, we use integrated mathematical modeling and experiments to understand how these feedback loops interact to control gibberellin signaling. Model simulations are in good agreement with in vitro data on the signal transduction and biosynthesis pathways and in vivo data on the expression levels of gibberellin-responsive genes. We find that GA-GID1 interactions are characterized by two timescales (because of a lid on GID1 that can open and close slowly relative to GA-GID1 binding and dissociation). Furthermore, the model accurately predicts the response to exogenous gibberellin after a number of chemical and genetic perturbations. Finally, we investigate the role of the various feedback loops in gibberellin signaling. We find that regulation of GA20ox transcription plays a significant role in both modulating the level of endogenous gibberellin and generating overshoots after the removal of exogenous gibberellin. Moreover, although the contribution of other individual feedback loops seems relatively small, GID1 and DELLA transcriptional regulation acts synergistically with GA20ox feedback.
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Affiliation(s)
- Alistair M. Middleton
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
- Zentrum für Biosystemanalyse, Albert-Ludwigs-Universität, 79104 Freiburg im Breisgau, Germany
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom; and
| | - Susana Úbeda-Tomás
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
| | - Jayne Griffiths
- Plant Science Department, Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom
| | - Tara Holman
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
| | - Peter Hedden
- Plant Science Department, Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom
| | - Stephen G. Thomas
- Plant Science Department, Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom
| | - Andrew L. Phillips
- Plant Science Department, Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom
| | - Michael J. Holdsworth
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
| | - Malcolm J. Bennett
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
| | - John R. King
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom; and
| | - Markus R. Owen
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom; and
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Turnbull MH, Pharis RP, Kurepin LV, Sarfati M, Mander LN, Kelly D. Flowering in snow tussock (Chionochloa spp.) is influenced by temperature and hormonal cues. FUNCTIONAL PLANT BIOLOGY : FPB 2012; 39:38-50. [PMID: 32480758 DOI: 10.1071/fp11116] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 10/17/2011] [Indexed: 06/11/2023]
Abstract
Snow tussocks (Chionochloa spp.) in New Zealand exhibit extreme mast (episodic) seeding which has important implications for plant ecology and plant-insect interactions. Heavy flowering appears to be triggered by very warm/dry summers in the preceding year. In order to investigate the physiological basis for mast flowering, mature snow tussock plants in the field and younger plants in a glasshouse and shadehouse were subjected to a range of manipulative treatments. Field treatments included combinations of warming, root pruning and applications of two native gibberellins (GAs) GA3, which is known to be highly floral inductive and GA4, which is associated with continued floral apex development in another long-day grass. Warming, GA3 alone and especially warming+GA3, significantly promoted flowering, as did applications of GA4 alone and GA4+CCC (2-chloroethyltrimethylammonium chloride, which is a known synergist of GA3-induced flowering in the annual grass, Lolium temulentum L.). Our results provide support for the concept that mast flowering events in tussock species are causally related to high temperature-induced increases in endogenous gibberellin levels. It is likely that GAs (endogenous or applied) promote the continued development of a previously long-day induced floral apex. In addition to the promotion of flowering, applied GA3 also disturbed the plant's innate resource threshold requirements, as shown by the death, over winter, of many non-flowering tillers. Applied GA4 did not show this effect, likely due to its rapid catabolic metabolism to an inactive form. High temperature-induced flowering mediated by elevated levels of endogenous floral-promotive GAs could have important implications for regulating the evolutionary interaction between these masting plants and their seed predators.
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Oracz K, Voegele A, Tarkowská D, Jacquemoud D, Turecková V, Urbanová T, Strnad M, Sliwinska E, Leubner-Metzger G. Myrigalone A inhibits Lepidium sativum seed germination by interference with gibberellin metabolism and apoplastic superoxide production required for embryo extension growth and endosperm rupture. PLANT & CELL PHYSIOLOGY 2012; 53:81-95. [PMID: 21908442 DOI: 10.1093/pcp/pcr124] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Myrica gale L. (sweet gale) fruit leachate contains myrigalone A (MyA), a rare C-methylated dihydrochalcone and putative allelochemical, which is known to be a phytotoxin impeding seedling growth. We found that MyA inhibited Lepidium sativum L. seed germination in a dose-dependent manner. MyA did not affect testa rupture, but inhibited endosperm rupture and the transition to subsequent seedling growth. MyA inhibited micropylar endosperm cap (CAP) weakening and the increase in the growth potential of the radical/hypocotyl region (RAD) of the embryo, both being key processes required for endosperm rupture. We compared the contents of abscisic acid (ABA) and gibberellins in the tissues and found that the major bioactive forms of gibberellin in L. sativum seed tissues were GA(4) and GA(6), while GA(8) and GA(13) were abundant inactive metabolites. MyA did not appreciably affect the ABA contents, but severely interfered with gibberellin metabolism and signaling by inhibiting important steps catalyzed by GA3 oxidase, as well as by interfering with the GID1-type gibberellin signaling pathway. The hormonally and developmentally regulated formation of apoplastic superoxide radicals is important for embryo growth. Specific zones within the RAD were associated with accumulation of apoplastic superoxide radicals and endoreduplication indicative of embryo cell extension. MyA negatively affected both of these processes and acted as a scavenger of apoplastic reactive oxygen species. We propose that MyA is an allelochemical with a novel mode of action on seed germination.
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Affiliation(s)
- Krystyna Oracz
- University of Freiburg, Faculty of Biology, Institute for Biology II, Botany/Plant Physiology, Freiburg, Germany.
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Lester DR, Phillips A, Hedden P, Andersson I. Purification and kinetic studies of recombinant gibberellin dioxygenases. BMC PLANT BIOLOGY 2005; 5:19. [PMID: 16181493 PMCID: PMC1262730 DOI: 10.1186/1471-2229-5-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Accepted: 09/25/2005] [Indexed: 05/04/2023]
Abstract
BACKGROUND The 2-oxoglutarate-dependent dioxygenases (2ODDs) of gibberellin (GA) biosynthesis have a key role in the metabolism of a major plant hormone. The activity of recombinant GA 2ODDs from many species has been characterised in detail, however little information relates to enzyme purification. Native GA 2ODDs displayed lability during purification. RESULTS Two GA 2ODDs were expressed in Escherichia coli and purified to homogeneity. The GA 2-oxidase from Pisum sativum L., PsGA2OX1, was expressed as a glutathione s-transferase (GST) fusion. It was purified in the three steps of affinity chromatography, GST removal and gel filtration. Highly pure PsGA2OX1 was obtained at a yield of 0.3 mg/g of cells. It displayed a Km of 0.024 microM and a Vmax of 4.4 pkat/mg toward [1beta,2beta,3beta-3H3]GA20. The GA 3-oxidase from Arabidopsis thaliana, AtGA3OX4, was expressed as a poly(His)-tagged thioredoxin fusion. It was purified by Immobilised Metal Affinity Chromatography followed by gel filtration. Cleavage of the fusion took place between the two purification steps. Highly pure AtGA3OX4 was obtained at a yield of 0.01 mg/g of cells. It displayed a Km of 0.82 microM and Vmax of 52,500 pkat/mg toward [1beta,2beta,3beta-3H3]GA20. CONCLUSION Fusion tags were required to stabilise and solubilise PsGA2OX1 and AtGA3OX4 during E. coli expression. The successful purification of milligram quantities of PsGA2OX1 enables mechanistic and structural studies not previously possible on GA 2ODDs. A moderate yield of pure AtGA3OX4 requires the further optimisation of the latter stages of the enzyme purification schedule. PsGA2OX1's action in planta as deduced from the effect of the null mutation sln on GA levels in seeds is in agreement with the kinetic parameters of the recombinant enzyme.
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Affiliation(s)
- Diane R Lester
- Institute for Cell and Molecular Biology, Uppsala University, Box 596, 751 24 Uppsala, Sweden
| | | | - Peter Hedden
- Rothamsted Research, Harpenden, Herts, AL5 2JQ UK
| | - Inger Andersson
- Department of Molecular Biology, Swedish University of Agricultural Sciences, Box 590, 751 24 Uppsala, Sweden
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