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Kumari K, Rai MP, Bansal N, Rama Prashat G, Kumari S, Krishnan V, Srivathsa R, Dahuja A, Sachdev A, Praveen S, Vinutha T. Analysis of γ-Tocopherol methyl transferase3 promoter activity and study of methylation patterns of the promoter and its gene body. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 144:375-385. [PMID: 31622940 DOI: 10.1016/j.plaphy.2019.09.044] [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: 08/13/2019] [Revised: 09/11/2019] [Accepted: 09/26/2019] [Indexed: 06/10/2023]
Abstract
Soybeans are known for its good source of protein (40%), oil (20%) and also serve as a source of nutraceutical compounds including tocopherols (toc). To know the molecular basis of differential α-toc accumulation in two contrasting soybean genotypes: DS74 (low α-toc - 1.36 μg/g and total-toc -29.72 μg/g) and Bragg (high α-toc - 10.48 μg/g and total-toc 178.91 μg/g), the analysis of γ-TMT3 promoter activity and its methylation patterns were carried out. The sequencing results revealed nucleotide variation between Bragg:γ-TMT3-P and DS74:γ-TMT3-P, however none of the variations were found in core-promoter region or in cis-elements. The histochemical GUS assay revealed higher promoter activity of Bragg:γ-TMT3-P than that of DS74:γ-TMT3-P and correlated with significantly higher and lower (P < 0.05) expression of γ-TMT3 gene respectively. To know the molecular basis of differential accumulation of α-toc in these contrasting soybean genotypes, the DNA methylation pattern of γ-TMT3 gene body and its promoter was studied in both varieties. The results showed higher percentage (62.5%) of methylation in DS74:γ-TMT3-P than in Bragg:γ-TMT3-P (50%). Out of all the methylation sites in the promoter region, one of methylation site was found at CAAT box (-190 bp) of DS74:γ-TMT3-P. Further gene body methylation patterns revealed lowest % (40%) of CG methylation in DS74:γ-TMT3 gene as compared to Bragg:γ-TMT3 (64.2%). Thus our study revealed that, expression of γ-TMT3 gene was influenced by its promoter activity and methylation patterns in cis-elements of γ-TMT3 promoter and gene body. This study will help us to understand the possible role of methylation and promoter activity in determining the α-toc content in soybean seeds.
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Affiliation(s)
- Khushboo Kumari
- Division of Biochemistry, IARI, New Delhi, 110012, India; Amity University, Noida, Uttar Pradesh, 201313, India
| | | | - Navita Bansal
- Division of Biochemistry, IARI, New Delhi, 110012, India; Amity University, Noida, Uttar Pradesh, 201313, India
| | | | - Sweta Kumari
- Division of Biochemistry, IARI, New Delhi, 110012, India
| | - Veda Krishnan
- Division of Biochemistry, IARI, New Delhi, 110012, India
| | - Rohini Srivathsa
- National Research Centre for Plant Biotechnology, Pusa, New Delhi, 110012, India
| | - Anil Dahuja
- Division of Biochemistry, IARI, New Delhi, 110012, India
| | | | - Shelly Praveen
- Division of Biochemistry, IARI, New Delhi, 110012, India.
| | - T Vinutha
- Division of Biochemistry, IARI, New Delhi, 110012, India.
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Zhang L, Luo Y, Liu B, Zhang L, Zhang W, Chen R, Wang L. Overexpression of the maize γ-tocopherol methyltransferase gene (ZmTMT) increases α-tocopherol content in transgenic Arabidopsis and maize seeds. Transgenic Res 2019; 29:95-104. [PMID: 31673914 DOI: 10.1007/s11248-019-00180-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/22/2019] [Indexed: 11/25/2022]
Abstract
The vitamin E family includes tocopherols and tocotrienols, which are essential lipid-soluble antioxidants necessary for human and livestock health. The seeds of many plant species, including maize, have high gamma (γ)-tocopherol but low alpha (α)-tocopherol contents; however, α-tocopherol is the most effective antioxidant. Therefore, it is necessary to optimize the tocopherol composition in plants. α-Tocopherol is synthesized from γ-tocopherol by γ-tocopherol methyltransferase (γ-TMT, VTE4) in the final step of the tocopherol biosynthetic pathway. In the present study, the full-length coding sequence (CDS) of γ-TMT was isolated from Zea mays, named ZmTMT. The ZmTMT CDS was 1059 bp in size, encoding 352 amino acids. Recombinant ZmTMT was expressed in Escherichia coli and the purified protein effectively converted γ-tocopherol into α-tocopherol in vitro. A comparison of enzyme activities showed that the activity of ZmTMT was higher than that of GmTMT2a (Glycine max) and AtTMT (Arabidopsis thaliana). Overexpression of ZmTMT increased the α-tocopherol content 4-5-fold in transgenic Arabidopsis and around 6.5-fold in transgenic maize kernels, and increased the α-/γ-tocopherol ratio to approximately 15 and 17, respectively. These results show that it is feasible to overexpress ZmTMT to optimize the tocopherol composition in maize; such a corn product might be useful in the feed industry in the near future.
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Affiliation(s)
- Lan Zhang
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Yanzhong Luo
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Bin Liu
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Liang Zhang
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Wei Zhang
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Rumei Chen
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Lei Wang
- National Key Facility of Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
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Tewari K, Kumar V, Kumar A, Bansal N, Vinutha T, Ali K, Sachdev A, Kumari S, Dahuja A. Molecular cloning and functional analysis of the promoter of γ-Tocopherol Methyl Transferase ( γ-TMT) gene of soybean ( Glycine max). 3 Biotech 2018; 8:325. [PMID: 30034989 DOI: 10.1007/s13205-018-1347-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Accepted: 07/10/2018] [Indexed: 11/26/2022] Open
Abstract
γ-Tocopherol methyl transferase (γ-TMT) (EC 2.1.1.95) is the key enzyme of the tocopherol biosynthetic pathway that determines the α-tocopherol concentration in plants. The overexpression of γ-TMT has been a successful approach for α-tocopherol enrichment of most plants including soybean. The typical soybean varieties are rich in γ-tocopherol (constitutes nearly 65-70% of its total seed tocopherol pool), while α-tocopherol, the biologically most active form among all tocopherols, constitutes only 10% of the total tocopherol content. The identification of soybean varieties that have seed α-tocopherol as high as > 20% of the total tocopherols has shifted attention towards the breeding based approach for α-tocopherol enrichment of this crop. Previous research on this aspect suggests that polymorphisms in γ-TMT promoter might be associated with the high α-tocopherol concentration of some soybean varieties. To understand the molecular basis of genetic variation for α-tocopherol concentration in Indian varieties of soybean we cloned the 1.4 kb upstream promoter region of γ-TMT from a high α-tocopherol containing soybean variety (Bragg) as well as from a low α-tocopherol containing variety (DS 2706). Cloning of each of these promoters in pORE R2 vector having GUS reporter gene and the subsequent GUS assay revealed a slightly high promoter activity of Bragg γ-TMT as compared to DS 2706 γ-TMT. On promoter sequence analysis, no sequence polymorphisms were observed in the core promoter region of this gene. However, seven single nucleotide polymorphisms (SNPs) were observed outside the core promoter region. Further study based on deletion construct analysis of this promoter will elucidate the significance of these SNPs in influencing the activity of γ-TMT promoter and the α-tocopherol concentration.
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Affiliation(s)
- Kalpana Tewari
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
- 2Basic Sciences Division, Indian Institute of Pulses Research, Kanpur, UP India
| | - Vaibhav Kumar
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
- 2Basic Sciences Division, Indian Institute of Pulses Research, Kanpur, UP India
| | - Amresh Kumar
- 3National Research Centre on Plant Biotechnology, New Delhi, India
| | - Navita Bansal
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - T Vinutha
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Kishwar Ali
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Archana Sachdev
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Sweta Kumari
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Anil Dahuja
- 1Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
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Rahikainen M, Alegre S, Trotta A, Pascual J, Kangasjärvi S. Trans-methylation reactions in plants: focus on the activated methyl cycle. PHYSIOLOGIA PLANTARUM 2018; 162:162-176. [PMID: 28815615 DOI: 10.1111/ppl.12619] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/02/2017] [Accepted: 08/10/2017] [Indexed: 05/11/2023]
Abstract
Trans-methylation reactions are vital in basic metabolism, epigenetic regulation, RNA metabolism, and posttranslational control of protein function and therefore fundamental in determining the physiological processes in all living organisms. The plant kingdom is additionally characterized by the production of secondary metabolites that undergo specific hydroxylation, oxidation and methylation reactions to obtain a wide array of different chemical structures. Increasing research efforts have started to reveal the enzymatic pathways underlying the biosynthesis of complex metabolites in plants. Further engineering of these enzymatic machineries offers significant possibilities in the development of bio-based technologies, but necessitates deep understanding of their potential metabolic and regulatory interactions. Trans-methylation reactions are tightly coupled with the so-called activated methyl cycle (AMC), an essential metabolic circuit that maintains the trans-methylation capacity in all living cells. Tight regulation of the AMC is crucial in ensuring accurate trans-methylation reactions in different subcellular compartments, cell types, developmental stages and environmental conditions. This review addresses the organization and posttranslational regulation of the AMC and elaborates its critical role in determining metabolic regulation through modulation of methyl utilization in stress-exposed plants.
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Affiliation(s)
- Moona Rahikainen
- Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland
| | - Sara Alegre
- Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland
| | - Andrea Trotta
- Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland
| | - Jesús Pascual
- Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland
| | - Saijaliisa Kangasjärvi
- Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland
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Tewari K, Dahuja A, Sachdev A, Kumar V, Ali K, Kumar A, Kumari S. Molecular cloning, heterologous expression and functional characterization of gamma tocopherol methyl transferase (γ-TMT) from Glycine max. Protein Expr Purif 2017; 140:81-89. [PMID: 28811265 DOI: 10.1016/j.pep.2017.08.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 07/09/2017] [Accepted: 08/10/2017] [Indexed: 11/30/2022]
Abstract
γ-Tocopherol methyltransferase (γ-TMT) (EC 2.1.1.95) is the last enzyme in the tocopherol biosynthetic pathway and it catalyzes the conversion of γ-tocopherol into α-tocopherol, the nutritionally significant and most bioactive form of vitamin E. Although the γ-TMT gene has been successfully overexpressed in many crops to enhance their α-tocopherol content but still only few attempts have been made to uncover its structural, functional and regulation aspects at protein level. In this study, we have cloned the complete 909bp coding sequence of Glycine max γ-TMT (Gm γ-TMT) gene that encodes the corresponding protein comprising of 302 amino acid residues. The deduced Gm γ-TMT protein showed 74-87% sequence identity with other characterized plant γ-TMTs. Gm γ-TMT belongs to Class I Methyl Transferases that have a Rossmann-like fold which consists of a seven-stranded β sheet joined by α helices. Heterologous expression of Gm γ-TMT in pET29a expression vector under the control of bacteriophage T7 promoter produced a 37.9 kDa recombinant Gm γ-TMT protein with histidine hexamer tag at its C-terminus. The expression of recombinant Gm γ-TMT protein was confirmed by western blotting using anti-His antibody. The recombinant protein was purified by Ni2+-NTA column chromatography. The purified protein showed SAM dependent methyltransferase activity. The α-tocopherol produced in the in-vitro reaction catalyzed by the purified enzyme was detected using reverse phase HPLC. This study has laid the foundation to unveil the biochemical understanding of Gm γ-TMT enzyme which can be further explored by studying its kinetic behaviour, substrate specificity and its interaction with other biomolecules.
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Affiliation(s)
- Kalpana Tewari
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India; Basic Sciences Division, Indian Institute of Pulses Research, Kanpur, U.P., India.
| | - Anil Dahuja
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Archana Sachdev
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Vaibhav Kumar
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India; Basic Sciences Division, Indian Institute of Pulses Research, Kanpur, U.P., India
| | - Kishwar Ali
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Amresh Kumar
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
| | - Sweta Kumari
- Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, India
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Ndikuryayo F, Moosavi B, Yang WC, Yang GF. 4-Hydroxyphenylpyruvate Dioxygenase Inhibitors: From Chemical Biology to Agrochemicals. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:8523-8537. [PMID: 28903556 DOI: 10.1021/acs.jafc.7b03851] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The development of new herbicides is receiving considerable attention to control weed biotypes resistant to current herbicides. Consequently, new enzymes are always desired as targets for herbicide discovery. 4-Hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) is an enzyme engaged in photosynthetic activity and catalyzes the transformation of 4-hydroxyphenylpyruvic acid (HPPA) into homogentisic acid (HGA). HPPD inhibitors constitute a promising area of discovery and development of innovative herbicides with some advantages, including excellent crop selectivity, low application rates, and broad-spectrum weed control. HPPD inhibitors have been investigated for agrochemical interests, and some of them have already been commercialized as herbicides. In this review, we mainly focus on the chemical biology of HPPD, discovery of new potential inhibitors, and strategies for engineering transgenic crops resistant to current HPPD-inhibiting herbicides. The conclusion raises some relevant gaps for future research directions.
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Affiliation(s)
- Ferdinand Ndikuryayo
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University , Wuhan 430079, P. R. China
| | - Behrooz Moosavi
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University , Wuhan 430079, P. R. China
| | - Wen-Chao Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University , Wuhan 430079, P. R. China
| | - Guang-Fu Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University , Wuhan 430079, P. R. China
- Collaborative Innovation Center of Chemical Science and Engineering , Tianjin 30071, P. R. China
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Gálvez-Valdivieso G, Cardeñosa R, Vera JM, Pineda M, Aguilar M. γ-Tocopherol methyltransferase from the green alga Chlamydomonas reinhardtii: functional characterization and expression analysis. PHYSIOLOGIA PLANTARUM 2011; 143:316-328. [PMID: 21883249 DOI: 10.1111/j.1399-3054.2011.01507.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
γ-Tocopherol methyltransferase (γ-TMT) (EC 2.1.1.95) is a very important enzyme in tocopherol biosynthesis in all photosynthetic organisms. In this paper, we present the functional characterization and expression analysis of γ-TMT from the unicellular green alga Chlamydomonas reinhardtii. Recombinant TMT1 enzyme was purified and characterized. The size of TMT1 subunit was estimated as 37 kDa by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), in accordance with the predicted molecular size after TMT1 cDNA sequence. Recombinant TMT1 also showed an apparent molecular mass of 37 kDa in its native conformation, suggesting that native TMT1 has a monomeric structure similar to the plant TMTs already characterized. pH and temperature dependence of TMT1 activity were also similar to plant TMTs. Substrate specificity studies showed that Chlamydomonas TMT1 is responsible for the conversion of γ- and δ-tocopherol to α- and β-tocopherol, respectively. The kinetic properties of Chlamydomonas recombinant γ-TMT activity were studied and γ-TMT1 has a similar affinity for γ- and δ-tocopherol. Promoter sequence analysis and expression analysis by northern blot revealed that tmt1 expression is strongly upregulated by high light and downregulated by low temperature. This regulatory pattern of tmt1 expression supports the idea that γ- and α-tocopherol play specific roles in the adaptation to growth under low temperature and high light stress conditions.
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Affiliation(s)
- Gregorio Gálvez-Valdivieso
- Departamento de Botánica, Ecología y Fisiología Vegetal, Instituto Andaluz de Biotecnología, Campus de Rabanales, Edif. C-4, 3a Planta, Universidad de Córdoba, 14071 Córdoba, Spain
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Barsan C, Sanchez-Bel P, Rombaldi C, Egea I, Rossignol M, Kuntz M, Zouine M, Latché A, Bouzayen M, Pech JC. Characteristics of the tomato chromoplast revealed by proteomic analysis. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:2413-31. [PMID: 20363867 DOI: 10.1093/jxb/erq070] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Chromoplasts are non-photosynthetic specialized plastids that are important in ripening tomato fruit (Solanum lycopersicum) since, among other functions, they are the site of accumulation of coloured compounds. Analysis of the proteome of red fruit chromoplasts revealed the presence of 988 proteins corresponding to 802 Arabidopsis unigenes, among which 209 had not been listed so far in plastidial databanks. These data revealed several features of the chromoplast. Proteins of lipid metabolism and trafficking were well represented, including all the proteins of the lipoxygenase pathway required for the synthesis of lipid-derived aroma volatiles. Proteins involved in starch synthesis co-existed with several starch-degrading proteins and starch excess proteins. Chromoplasts lacked proteins of the chlorophyll biosynthesis branch and contained proteins involved in chlorophyll degradation. None of the proteins involved in the thylakoid transport machinery were discovered. Surprisingly, chromoplasts contain the entire set of Calvin cycle proteins including Rubisco, as well as the oxidative pentose phosphate pathway (OxPPP). The present proteomic analysis, combined with available physiological data, provides new insights into the metabolic characteristics of the tomato chromoplast and enriches our knowledge of non-photosynthetic plastids.
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Affiliation(s)
- Cristina Barsan
- Université de Toulouse, INP-ENSA Toulouse, Génomique et Biotechnologie des Fruits, Avenue de l'Agrobiopole BP 32607, F-31326 Castanet-Tolosan, France
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Peuthert A, Pflugmacher S. Influence of the cyanotoxin microcystin-LR on tocopherol in Alfalfa seedlings (Medicago sativa). Toxicon 2010; 56:411-7. [PMID: 20398686 DOI: 10.1016/j.toxicon.2010.04.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 03/26/2010] [Accepted: 04/07/2010] [Indexed: 10/19/2022]
Abstract
Spray irrigation of crop plants can represent a risk if the water is contaminated with cyanotoxins. These secondary metabolites produced by many cyanobacteria can have adverse effects on organisms, among others the induction of excess oxygen radicals, so-called oxidative stress. Thereby tocopherol as a lipid antioxidant is essential to maintain membrane integrity. In this study the effects of the cyanotoxin microcystin-LR (MC-LR), and a Microcystis crude extract (Mic-CE) containing MC-LR on tocopherol content and gene expression of Homogentisate phytyltransferase (HPT), involved in tocopherol synthesis, were investigated in seedlings of the crop plant Medicago sativa. Exposures to environmental relevant concentrations showed that Mic-CE affects the tocopherols at a lower concentration than the pure toxin. Changes during a 3-day exposure using 0.5mug L(-1) MC-LR and Mic-CE revealed strong increases of alpha- and beta-tocopherol content, whereas the influence on beta-tocopherol was far stronger than on alpha-tocopherol. The HPT mRNA was elevated after 24 and 72h exposure to MC-LR. These results show that also low concentrations of cyanobacterial toxins in the water have strong influence on tocopherol in M. sativa seedlings and therefore represent a stress for the plants.
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Affiliation(s)
- Anja Peuthert
- Leibniz Institute of Freshwater Ecology and Inland Fisheries, Department of Aquaculture and Ecophysiology, Müggelseedamm 301, 12587 Berlin, Germany
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Hunter SC, Cahoon EB. Enhancing vitamin E in oilseeds: unraveling tocopherol and tocotrienol biosynthesis. Lipids 2007; 42:97-108. [PMID: 17393215 DOI: 10.1007/s11745-007-3028-6] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 01/17/2007] [Indexed: 11/24/2022]
Abstract
Naturally occurring vitamin E, comprised of four forms each of tocopherols and tocotrienols, are synthesized solely by photosynthetic organisms and function primarily as antioxidants. These different forms vary in their biological availability and in their physiological and chemical activities. Tocopherols and tocotrienols play important roles in the oxidative stability of vegetable oils and in the nutritional quality of crop plants for human and livestock diets. The isolation of genes for nearly all the steps in tocopherol and tocotrienol biosynthesis has facilitated efforts to alter metabolic flux through these pathways in plant cells. Herein we review the recent work done in the field, focusing on branch points and metabolic engineering to enhance and alter vitamin E content and composition in oilseed crops.
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Affiliation(s)
- Sarah C Hunter
- United States Department of Agriculture, ARS, Plant Genetics Research Unit, Donald Danforth Plant Science Center, 975 North Warson Road, Saint Louis, MO 63132, USA.
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Tavva VS, Kim YH, Kagan IA, Dinkins RD, Kim KH, Collins GB. Increased alpha-tocopherol content in soybean seed overexpressing the Perilla frutescens gamma-tocopherol methyltransferase gene. PLANT CELL REPORTS 2007; 26:61-70. [PMID: 16909228 DOI: 10.1007/s00299-006-0218-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 07/10/2006] [Accepted: 07/15/2006] [Indexed: 05/11/2023]
Abstract
Tocopherols, with antioxidant properties, are synthesized by photosynthetic organisms and play important roles in human and animal nutrition. In soybean, gamma-tocopherol, the biosynthetic precursor to alpha-tocopherol, is the predominant form found in the seed, whereas alpha-tocopherol is the most bioactive component. This suggests that the final step of the alpha-tocopherol biosynthetic pathway catalyzed by gamma-tocopherol methyltransferase (gamma-TMT) is limiting in soybean seed. Soybean oil is the major edible vegetable oil consumed, so manipulating the tocopherol biosynthetic pathway in soybean seed to convert tocopherols into more active alpha-tocopherol form could have significant health benefits. In order to increase the soybean seed alpha-tocopherol content, the gamma-TMT gene isolated from Perilla frutescens was overexpressed in soybean using a seed-specific promoter. One transgenic plant was recovered and the progeny was analyzed for two generations. Our results demonstrated that the seed-specific expression of the P. frutescens gamma-TMT gene resulted in a 10.4-fold increase in the alpha-tocopherol content and a 14.9-fold increase in the beta-tocopherol content in T2 seed. Given the relative contributions of different tocopherols to vitamin E activity, the activity in T2 seed was calculated to be 4.8-fold higher than in wild-type seed. In addition, the data obtained on lipid peroxidation indicates that alpha-tocopherol may have a role in preventing oxidative damage to lipid components during seed storage and seed germination. The increase in the alpha-tocopherol content in the soybean seed could have a potential to significantly increase the dietary intake of vitamin E.
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Affiliation(s)
- Venkata S Tavva
- Department of Plant and Soil Sciences, University of Kentucky, 1405 Veterans Road, Lexington, KY 40546-0312, USA
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Palmieri L, Arrigoni R, Blanco E, Carrari F, Zanor MI, Studart-Guimaraes C, Fernie AR, Palmieri F. Molecular identification of an Arabidopsis S-adenosylmethionine transporter. Analysis of organ distribution, bacterial expression, reconstitution into liposomes, and functional characterization. PLANT PHYSIOLOGY 2006; 142:855-65. [PMID: 16950860 PMCID: PMC1630753 DOI: 10.1104/pp.106.086975] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Despite much study of the role of S-adenosylmethionine (SAM) in the methylation of DNA, RNA, and proteins, and as a cofactor for a wide range of biosynthetic processes, little is known concerning the intracellular transport of this essential metabolite. Screening of the Arabidopsis (Arabidopsis thaliana) genome yielded two potential homologs of yeast (Saccharomyces cerevisiae) and human SAM transporters, designated as SAMC1 and SAMC2, both of which belong to the mitochondrial carrier protein family. The SAMC1 gene is broadly expressed at the organ level, although only in specialized tissues of roots with high rates of cell division, and appears to be up-regulated in response to wounding stress, whereas the SAMC2 gene is very poorly expressed in all organs/tissues analyzed. Direct transport assays with the recombinant and reconstituted SAMC1 were utilized to demonstrate that this protein displays a very narrow substrate specificity confined to SAM and its closest analogs. Further experiments revealed that SAMC1 was able to function in uniport and exchange reactions and characterized the transporter as highly active, but sensitive to physiologically relevant concentrations of S-adenosylhomocysteine, S-adenosylcysteine, and adenosylornithine. Green fluorescent protein-based cell biological analysis demonstrated targeting of SAMC1 to mitochondria. Previous proteomic analyses identified this protein also in the chloroplast inner envelope. In keeping with these results, bioinformatics predicted dual localization for SAMC1. These findings suggest that the provision of cytosolically synthesized SAM to mitochondria and possibly also to plastids is mediated by SAMC1 according to the relative demands for this metabolite in the organelles.
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Affiliation(s)
- Luigi Palmieri
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, 70125 Bari, Italy
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Bouvier F, Linka N, Isner JC, Mutterer J, Weber APM, Camara B. Arabidopsis SAMT1 defines a plastid transporter regulating plastid biogenesis and plant development. THE PLANT CELL 2006; 18:3088-105. [PMID: 17098813 PMCID: PMC1693945 DOI: 10.1105/tpc.105.040741] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Revised: 09/01/2006] [Accepted: 10/24/2006] [Indexed: 05/12/2023]
Abstract
S-Adenosylmethionine (SAM) is formed exclusively in the cytosol but plays a major role in plastids; SAM can either act as a methyl donor for the biogenesis of small molecules such as prenyllipids and macromolecules or as a regulator of the synthesis of aspartate-derived amino acids. Because the biosynthesis of SAM is restricted to the cytosol, plastids require a SAM importer. However, this transporter has not yet been identified. Here, we report the molecular and functional characterization of an Arabidopsis thaliana gene designated SAM TRANSPORTER1 (SAMT1), which encodes a plastid metabolite transporter required for the import of SAM from the cytosol. Recombinant SAMT1 produced in yeast cells, when reconstituted into liposomes, mediated the counter-exchange of SAM with SAM and with S-adenosylhomocysteine, the by-product and inhibitor of transmethylation reactions using SAM. Insertional mutation in SAMT1 and virus-induced gene silencing of SAMT1 in Nicotiana benthamiana caused severe growth retardation in mutant plants. Impaired function of SAMT1 led to decreased accumulation of prenyllipids and mainly affected the chlorophyll pathway. Biochemical analysis suggests that the latter effect represents one prominent example of the multiple events triggered by undermethylation, when there is decreased SAM flux into plastids.
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Affiliation(s)
- Florence Bouvier
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique and Université Louis Pasteur, 67084 Strasbourg Cedex, France
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15
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Shintani DK. Engineering plants for increased nutrition and antioxidant content through the manipulation of the vitamin E pathway. GENETIC ENGINEERING 2006; 27:231-42. [PMID: 16382879 DOI: 10.1007/0-387-25856-6_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Affiliation(s)
- David K Shintani
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA
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16
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Valentin HE, Qi Q. Biotechnological production and application of vitamin E: current state and prospects. Appl Microbiol Biotechnol 2005; 68:436-44. [PMID: 16041505 DOI: 10.1007/s00253-005-0017-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2005] [Revised: 05/09/2005] [Accepted: 05/19/2005] [Indexed: 10/25/2022]
Abstract
Tocochromanols (tocopherols and tocotrienols) are important lipophilic antioxidants for animals and humans. Their biological activity is expressed as vitamin E activity. This article describes the current need for vitamin E production, and compares different strategies to engineer the vitamin E content in photosynthetic bacteria and plants, with a focus on oilseed as target tissues. The current status of biotechnological advances in tocochromanol pathway engineering is summarized, and current limitations in our understanding of the tocochromanol biosynthetic pathway are discussed.
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Affiliation(s)
- Henry E Valentin
- Monsanto Co., Calgene Campus 1920 5th Street, Davis, CA 95616, USA.
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17
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Abstract
Isoprenoids represent the oldest class of known low molecular-mass natural products synthesized by plants. Their biogenesis in plastids, mitochondria and the endoplasmic reticulum-cytosol proceed invariably from the C5 building blocks, isopentenyl diphosphate and/or dimethylallyl diphosphate according to complex and reiterated mechanisms. Compounds derived from the pathway exhibit a diverse spectrum of biological functions. This review centers on advances obtained in the field based on combined use of biochemical, molecular biology and genetic approaches. The function and evolutionary implications of this metabolism are discussed in relation with seminal informations gathered from distantly but related organisms.
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Affiliation(s)
- Florence Bouvier
- Institut de Biologie Moléculaire des Plantes du CNRS (UPR2357) et Université Louis Pasteur, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France
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Backasch N, Schulz-Friedrich R, Appel J. Influences on tocopherol biosynthesis in the cyanobacterium Synechocystis sp. PCC 6803. JOURNAL OF PLANT PHYSIOLOGY 2005; 162:758-66. [PMID: 16008100 DOI: 10.1016/j.jplph.2005.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
To elucidate influences on the tocopherol biosynthesis in cyanobacteria, wild type and mutant cells of a putative methyltransferase in tocopherol and plastoquinone biosynthesis of Synechocystis sp. PCC 6803 were grown under different conditions. The vitamin E content of cells grown under different light regimes, photomixotrophic or photoautotrophic conditions and varying carbon dioxide supplies were compared by HPLC measurements. The tocopherol levels in wild type cells increased under higher light conditions and low carbon dioxide supply. Photomixotrophic growth led to lower vitamin E amounts in the cells compared to those grown photoautotrophically. We were able to segregate a homozygous deltasll0418 mutant under photoautotrophic conditions. In contrast to former suggestions in the literature the deletion of this gene is not lethal under photomixotrophic conditions and the influence on tocopherol and plastoquinone amounts is diminutive. The methyltransferase encoded by the gene sll0418 is not essential either for tocopherol or plastoquinone synthesis.
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Affiliation(s)
- Ninja Backasch
- Institute of Botany, Christian-Albrechts-University of Kiel, Olshausenstr, 40, 24098 Kiel, Germany
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19
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Abstract
Our understanding of the role of vitamin E in human nutrition, health, and disease has broadened and changed over the past two decades. Viewed initially as nature's most potent lipid-soluble antioxidant (and discovered for its crucial role in mammalian reproduction) we have now come to realize that vitamin E action has many more facets, depending on the physiological context. Although mainly acting as an antioxidant, vitamin E can also be a pro-oxidant; it can even have nonantioxidant functions: as a signaling molecule, as a regulator of gene expression, and, possibly, in the prevention of cancer and atherosclerosis. Since the term vitamin E encompasses a group of eight structurally related tocopherols and tocotrienols, individual isomers have different propensities with respect to these novel, nontraditional roles. The particular beneficial effects of the individual isomers have to be considered when dissecting the physiological impact of dietary vitamin E or supplements (mainly containing only the alpha-tocopherol isomer) in clinical trials. These considerations are also relevant for the design of transgenic crop plants with the goal of enhancing vitamin E content because an engineered biosynthetic pathway may be biased toward formation of one isomer. In contrast to the tremendous recent advances in knowledge of vitamin E chemistry and biology, there is little hard evidence from clinical and epidemiologic studies on the beneficial effects of supplementation with vitamin E beyond the essential requirement.
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Affiliation(s)
- Claus Schneider
- Division of Clinical Pharmacology, Department of Pharmacology, Vanderbilt University Medical School, Nashville, TN 37232-6602, USA.
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20
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Stocker A, Woggon WD, Rüttimann A. Identification of The Tocopherol-Cyclase in the Blue-Green AlgaeAnabaena variabilisKÜTZING(Cyanobacteria). Helv Chim Acta 2004. [DOI: 10.1002/hlca.19930760429] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Collakova E, DellaPenna D. The role of homogentisate phytyltransferase and other tocopherol pathway enzymes in the regulation of tocopherol synthesis during abiotic stress. PLANT PHYSIOLOGY 2003; 133:930-40. [PMID: 14512521 PMCID: PMC219066 DOI: 10.1104/pp.103.026138] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2003] [Revised: 06/16/2003] [Accepted: 07/20/2003] [Indexed: 05/18/2023]
Abstract
Tocopherols are amphipathic antioxidants synthesized exclusively by photosynthetic organisms. Tocopherol levels change significantly during plant growth and development and in response to stress, likely as a consequence of the altered expression of pathway-related genes. Homogentisate phytyltransferase (HPT) is a key enzyme limiting tocopherol biosynthesis in unstressed Arabidopsis leaves (E. Collakova, D. DellaPenna [2003] Plant Physiol 131: 632-642). Wild-type and transgenic Arabidopsis plants constitutively overexpressing HPT (35S::HPT1) were subjected to a combination of abiotic stresses for up to 15 d and tocopherol levels, composition, and expression of several tocopherol pathway-related genes were determined. Abiotic stress resulted in an 18- and 8-fold increase in total tocopherol content in wild-type and 35S::HPT1 leaves, respectively, with tocopherol levels in 35S::HPT1 being 2- to 4-fold higher than wild type at all experimental time points. Increased total tocopherol levels correlated with elevated HPT mRNA levels and HPT specific activity in 35S::HPT1 and wild-type leaves, suggesting that HPT activity limits total tocopherol synthesis during abiotic stress. In addition, substrate availability and expression of pathway enzymes before HPT also contribute to increased tocopherol synthesis during stress. The accumulation of high levels of beta-, gamma-, and delta-tocopherols in stressed tissues suggested that the methylation of phytylquinol and tocopherol intermediates limit alpha-tocopherol synthesis. Overexpression of gamma-tocopherol methyltransferase in the 35S::HPT1 background resulted in nearly complete conversion of gamma- and delta-tocopherols to alpha- and beta-tocopherols, respectively, indicating that gamma-tocopherol methyltransferase activity limits alpha-tocopherol synthesis in stressed leaves.
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Affiliation(s)
- Eva Collakova
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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23
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Collakova E, DellaPenna D. Homogentisate phytyltransferase activity is limiting for tocopherol biosynthesis in Arabidopsis. PLANT PHYSIOLOGY 2003; 131:632-42. [PMID: 12586887 PMCID: PMC166839 DOI: 10.1104/pp.015222] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2002] [Revised: 10/16/2002] [Accepted: 11/04/2002] [Indexed: 05/18/2023]
Abstract
Tocopherols are essential components of the human diet and are synthesized exclusively by photosynthetic organisms. These lipophilic antioxidants consist of a chromanol ring and a 15-carbon tail derived from homogentisate (HGA) and phytyl diphosphate, respectively. Condensation of HGA and phytyl diphosphate, the committed step in tocopherol biosynthesis, is catalyzed by HGA phytyltransferase (HPT). To investigate whether HPT activity is limiting for tocopherol synthesis in plants, the gene encoding Arabidopsis HPT, HPT1, was constitutively overexpressed in Arabidopsis. In leaves, HPT1 overexpression resulted in a 10-fold increase in HPT specific activity and a 4.4-fold increase in total tocopherol content relative to wild type. In seeds, HPT1 overexpression resulted in a 4-fold increase in HPT specific activity and a total seed tocopherol content that was 40% higher than wild type, primarily because of an increase in gamma-tocopherol content. This enlarged pool of gamma-tocopherol was almost entirely converted to alpha-tocopherol by crossing HPT1 overexpressing plants with lines constitutively overexpressing gamma-tocopherol methyltransferase. Seed of the resulting double overexpressing lines had a 12-fold increase in vitamin E activity relative to wild type. These results indicate that HPT activity is limiting in various Arabidopsis tissues and that total tocopherol levels and vitamin E activity can be elevated in leaves and seeds by combined overexpression of the HPT1 and gamma-tocopherol methyltransferase genes.
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Affiliation(s)
- Eva Collakova
- Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824, USA
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24
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Koch M, Lemke R, Heise KP, Mock HP. Characterization of gamma-tocopherol methyltransferases from Capsicum annuum L and Arabidopsis thaliana. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:84-92. [PMID: 12492478 DOI: 10.1046/j.1432-1033.2003.03364.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Tocopherols are essential micronutrients in human and animal nutrition due to their function as lipophilic antioxidants. They are exclusively synthesized by photosynthetic organisms including higher plants. Despite the attributed beneficial health effects and many industrial applications, research on the tocopherol biosynthetic pathway and its regulation in plants is still limited. In the work presented here we performed a detailed biochemical characterization of a gamma-tocopherol methyltransferase (gamma-TMT) from Arabidopsis thaliana and of a gamma-TMT purified from Capsicum annuum fruits, a tissue with high accumulation of tocopherols. The biochemical characteristics of both enzyme preparations were remarkably similar including substrate specificities. Both enzymes converted delta- and gamma- into beta- and alpha-tocopherol, respectively, but beta-tocopherol was not accepted as a substrate, pointing to a specific methylation at the C(5)-position of the tocopherol aromatic head group. A kinetic analysis performed with the Arabidopsis enzyme was consistent with an iso-ordered bi-bi type reaction mechanism. Our results emphasize the role of gamma-TMT in regulating the spectrum of accumulated tocopherols in plants.
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Affiliation(s)
- Maria Koch
- Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany
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25
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Yamamoto Y, Fujisawa A, Hara A, Dunlap WC. An unusual vitamin E constituent (alpha-tocomonoenol) provides enhanced antioxidant protection in marine organisms adapted to cold-water environments. Proc Natl Acad Sci U S A 2001; 98:13144-8. [PMID: 11687648 PMCID: PMC60838 DOI: 10.1073/pnas.241024298] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A new vitamin E constituent having an unusual methylene unsaturation at the isoprenoid-chain terminus of alpha-tocopherol (alpha-Toc) was isolated from chum salmon eggs and was found to have identical antioxidant activity as does alpha-Toc in methanol or liposomal suspension at 37 degrees C. Here we report that this marine-derived tocopherol (MDT) is broadly distributed with alpha-Toc in the tissue of marine fish, and that the MDT composition of total vitamin E is greater in the flesh of cold-water salmon (12-20%) than in that of tropical fish (< or =2.5%). Vitamin E analysis of cultured masu salmon maintained on a MDT-deplete diet showed substantially less MDT content than native masu salmon, suggesting a trophic origin of MDT. This contention is supported by the finding of MDT in marine plankton from the cold waters of Hokkaido. We found that MDT inhibited peroxidation of cholesterol-containing phosphatidylcholine liposomes to a greater extent than did alpha-Toc at 0 degrees C. Furthermore, the ratios of the rate constants for MDT and alpha-Toc to scavenge peroxyl radicals increased with decreasing rates of radical flux in liposomes and fish oil at 0 degrees C, indicating that the enhanced activity of MDT at low temperature is attributed to its greater rate of diffusion in viscous lipids. These results suggest that MDT production, or its trophic accumulation, may reduce lipid peroxidation in marine organisms functionally adapted to cold-water environments.
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Affiliation(s)
- Y Yamamoto
- Department of Chemistry and Biotechnology, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
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26
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27
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Grusak MA, DellaPenna D. IMPROVING THE NUTRIENT COMPOSITION OF PLANTS TO ENHANCE HUMAN NUTRITION AND HEALTH. ACTA ACUST UNITED AC 1999; 50:133-161. [PMID: 15012206 DOI: 10.1146/annurev.arplant.50.1.133] [Citation(s) in RCA: 220] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Plant foods contain almost all of the mineral and organic nutrients established as essential for human nutrition, as well as a number of unique organic phytochemicals that have been linked to the promotion of good health. Because the concentrations of many of these dietary constituents are often low in edible plant sources, research is under way to understand the physiological, biochemical, and molecular mechanisms that contribute to their transport, synthesis and accumulation in plants. This knowledge can be used to develop strategies with which to manipulate crop plants, and thereby improve their nutritional quality. Improvement strategies will differ between various nutrients, but generalizations can be made for mineral or organic nutrients. This review focuses on the plant nutritional physiology and biochemistry of two essential human nutrients, iron and vitamin E, to provide examples of the type of information that is needed, and the strategies that can be used, to improve the mineral or organic nutrient composition of plants.
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Affiliation(s)
- Michael A. Grusak
- Department of Pediatrics, Baylor College of Medicine, USDA/ARS Children's Nutrition Research Center, Houston, Texas 77030; e-mail: , Department of Biochemistry, University of Nevada, Reno, Nevada 89557; e-mail:
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28
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Abstract
alpha-Tocopherol (vitamin E) is a lipid-soluble antioxidant synthesized only by photosynthetic organisms. alpha-Tocopherol is an essential component of mammalian diets, and intakes in excess of the U.S. recommended daily allowance are correlated with decreased incidence of a number of degenerative human diseases. Plant oils, the main dietary source of tocopherols, typically contain alpha-tocopherol as a minor component and high levels of its biosynthetic precursor, gamma-tocopherol. A genomics-based approach was used to clone the final enzyme in alpha-tocopherol synthesis, gamma-tocopherol methyltransferase. Overexpression of gamma-tocopherol methyltransferase in Arabidopsis seeds shifted oil compositions in favor of alpha-tocopherol. Similar increases in agricultural oil crops would increase vitamin E levels in the average U.S. diet.
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Affiliation(s)
- D Shintani
- Department of Biochemistry, Mail Stop 200, University of Nevada, Reno, NV 89557, USA
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29
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Stocker A, Fretz H, Frick H, Rüttimann A, Woggon WD. The substrate specificity of tocopherol cyclase. Bioorg Med Chem 1996; 4:1129-34. [PMID: 8831985 DOI: 10.1016/0968-0896(96)00125-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The substrate specificity of the enzyme tocopherol cyclase from the blue-green algae Anabaena variabilis (Cyanobacteria) was investigated with 11 substrate analogues revealing the significance of three major recognition sites: (i) the OH group at C(1) of the hydroquinone, (ii) the (E) configuration of the double bond, and (iii) the length of the lipophilic side chain. Experiments with two affinity matrices suggest that substrates approach the enzyme's active site with the hydrophobic tail.
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Affiliation(s)
- A Stocker
- Organisch-chemisches Institut der Universität Zürich, Switzerland
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30
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Camara B, Hugueney P, Bouvier F, Kuntz M, Monéger R. Biochemistry and molecular biology of chromoplast development. INTERNATIONAL REVIEW OF CYTOLOGY 1995; 163:175-247. [PMID: 8522420 DOI: 10.1016/s0074-7696(08)62211-1] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Plant cells contain a unique class of organelles, designated the plastids, which distinguish them from animal cells. According to the largely accepted endosymbiotic theory of evolution, plastids are descendants of prokaryotes. This process requires several adaptative changes which involve the maintenance and the expression of part of the plastid genome, as well as the integration of the plastid activity to the cellular metabolism. This is illustrated by the diversity of plastids encountered in plant cells. For instance, in tissues undergoing color changes, i.e., flowers and fruits, the chromoplasts produce and accumulate excess carotenoids. In this paper we attempt to review the basic aspects of chromoplast development.
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Affiliation(s)
- B Camara
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Strasbourg, France
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31
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Joyard J, Block MA, Douce R. Molecular aspects of plastid envelope biochemistry. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 199:489-509. [PMID: 1868841 DOI: 10.1111/j.1432-1033.1991.tb16148.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- J Joyard
- Département de Biologie Moléculaire et Structurale, Université Joseph Fourier, Grenoble, France
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32
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Affiliation(s)
- R Bentley
- Department of Chemistry, University of Sheffield, U.K
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33
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Carde JP, Camara B, Cheniclet C. Absence of ribosomes in Capsicum chromoplasts. PLANTA 1988; 173:1-11. [PMID: 24226172 DOI: 10.1007/bf00394480] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/1987] [Accepted: 07/01/1987] [Indexed: 06/02/2023]
Abstract
Ribosome development was followed by electron microscopy and gel electrophoresis of ribosomal (r)RNAs in the plastids of fully expanded fruits of Capsicum annuum L. during ripening. Chloroplasts from young Capsicum leaves were used as a structural and electrophoretic standard. Four stages were distinguished on the basis of colour changes during fruit ripening. Chloroplasts of the green fruit had a lower content of 16S and 23S rRNAs than leaf chloroplasts. They contained only a few ribosomes, some more discrete "ribosomal particles", and the contrast of ribosomal structures was faint. From the outset of ripening, most of the ribosomal structures in the plastid stroma disappeared. A continuous decrease in plastid rRNAs occurred during ripening. Fully differentiated chromoplasts of the red fruit did not contain rRNAs or ribosomes. Throughout plastid development, DNA nucleoids were evident and there was only a small decrease in the DNA peak on electrophoretograms. The loss of ribosomes during the chloroplast-to-chromoplast conversion in Capsicum fruit is discussed in relation to the variations in pigments and enzymic systems in both plastid types.
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Affiliation(s)
- J P Carde
- Laboratoire de Physiologie cellulaire végétale, U.A. au C.N.R.S. no 568, Université Bordeaux I, Avenue des facultés, F-33405, Talence Cedex, France
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