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WO1998042848A1 - Proteines purifiees, sequences d'adn recombinees, et procedes de fabrication de boissons decafeinees - Google Patents

Proteines purifiees, sequences d'adn recombinees, et procedes de fabrication de boissons decafeinees Download PDF

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Publication number
WO1998042848A1
WO1998042848A1 PCT/US1998/005557 US9805557W WO9842848A1 WO 1998042848 A1 WO1998042848 A1 WO 1998042848A1 US 9805557 W US9805557 W US 9805557W WO 9842848 A1 WO9842848 A1 WO 9842848A1
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leu
asn
gly
ala
ser
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PCT/US1998/005557
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John I. Stiles
Istefo Moisyadi
Kabi Raj Neupane
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University Of Hawaii
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Priority claimed from PCT/US1997/004982 external-priority patent/WO1997035960A1/fr
Application filed by University Of Hawaii filed Critical University Of Hawaii
Priority to PCT/US1998/005557 priority Critical patent/WO1998042848A1/fr
Priority to AU67668/98A priority patent/AU6766898A/en
Publication of WO1998042848A1 publication Critical patent/WO1998042848A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/10—Transferases (2.)
    • C12N9/1003—Transferases (2.) transferring one-carbon groups (2.1)
    • C12N9/1007—Methyltransferases (general) (2.1.1.)
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
    • C12N15/79—Vectors or expression systems specially adapted for eukaryotic hosts
    • C12N15/82—Vectors or expression systems specially adapted for eukaryotic hosts for plant cells, e.g. plant artificial chromosomes (PACs)
    • C12N15/8241—Phenotypically and genetically modified plants via recombinant DNA technology
    • C12N15/8242—Phenotypically and genetically modified plants via recombinant DNA technology with non-agronomic quality (output) traits, e.g. for industrial processing; Value added, non-agronomic traits
    • C12N15/8243—Phenotypically and genetically modified plants via recombinant DNA technology with non-agronomic quality (output) traits, e.g. for industrial processing; Value added, non-agronomic traits involving biosynthetic or metabolic pathways, i.e. metabolic engineering, e.g. nicotine, caffeine

Definitions

  • This application relates to purified proteins, recombinant DNA sequences, hosts transformed therewith and processes for producing caffeine-free beverages and food products. More particularly, this application relates to purified proteins, and recombinant DNA sequences that suppress the expression of caffeine in coffee plants, and in fruit harvested therefrom.
  • the invention produces stable lines of caffeine free coffee plants whose fruit, after roasting and grinding, can be used to prepare caffeine free coffee. It is expected that the invention can be used to suppress caffeine synthesis in tea (Camellia sinensis and cola (Cola acuminata), as well as related alkaloids in chocolate (Theobroma cacao).
  • Coffee is prepared from the roasted ground beans of the plants of the genus Coffea. generally from the species C. arabica. Coffee plants produce the alkaloid caffeine, which is present in their dried fruit, coffee beans. Because many coffee drinkers prefer coffee without caffeine, a number of processes have been developed to remove caffeine from coffee beans. All of these processes result in the removal of substances other than caffeine from the beans, thereby adversely affecting the taste of coffee brewed from the treated beans. Although a few naturally occurring caffeine free coffees and related genera are known (Mascarocoffea spp. and Coffea bengalensisl they have no commercial value. (Charrier and Berthaud, "Variation Of Caffeine Content In The Coffea Genus", Cafe' Cacao The'. 14:251-264 (1975)). Accordingly, there is a need for a method for producing decaffeinated coffee beans that does not result in the removal of substances from the beans other than caffeine.
  • Caffeine is a naturally occurring purine alkaloid produced by coffee and tea plants, among others. It is believed that caffeine synthesis protects the plants from insects. Coffee plants synthesize caffeine from the nucleoside xanthosine in four sequential reactions as shown in Figure 1. For review see Suzuki, T., Ashihara, H. and Waller, G.R., Phvtochemistrv 31_:2575 (1992). The first step in the pathway is the methylation of the nucleoside xanthosine by S-adenosylmethionine, which is catalyzed by the enzyme xanthosine N " - 7 methyl transferase (XMT).
  • XMT xanthosine N " - 7 methyl transferase
  • T e product 7-methylxanthosine is hydrolyzed (a ribose is removed) to 7-methylxanthine, and undergoes further methylations to theobromine and caffeine. It is to be expected that interruption of this sequence of synthetic reactions would block caffeine synthesis.
  • a strategy for selectively eliminating caffeine from coffee plants is to prevent synthesis of specific enzymes in the pathway for caffeine biosynthesis.
  • this invention relates to genetic alteration of coffee plants to eliminate synthesis of XMT.
  • synthesis of XMT is suppressed by transforming coffee plants with a DNA sequence that codes on transcription for a messenger RNA (mRNA) that is antisense to the mRNA that codes on expression for XMT.
  • mRNA messenger RNA
  • the invention may be generalized to produce other caffeine free beverages and food products, including tea, cocoa, and other chocolate-based beverages or foods.
  • the DNA sequences and recombinant DNA molecules are characterized in that they code on expression for an enzyme, xanthosine N' methyl transferase (XMT), that is the first step in the pathway for caffeine synthesis in coffee.
  • XMT xanthosine N' methyl transferase
  • Coffee plants are transformed with DNA molecules that code on transcription for mRNA that is antisense to mRNA that codes on expression for at least one enzyme in the pathway for caffeine biosynthesis.
  • the antisense RNA binds to XMT mRNA, thereby inactivating the mRNA encoding the first step in the pathway for caffeine synthesis. The result is that the transformed plants are incapable of synthesizing caffeine, though other aspects of their metabolism is not affected.
  • Figure 1 is a schematic drawing of the pathway for caffeine synthesis in Coffea arabica.
  • Figure 2 is a photograph of a silver stained SDS PAGE gel of purified xanthosine N? methyl transferase.
  • Figure 3 is a densitometric plot showing elution of tryptic fragments of purified xanthosine N methyl transferase following HPLC separation.
  • Figure 4 is a description of the oligonucleotide primers used to screen the cDNA library cDNA encoding xanthosine N ' methyl transferase.
  • Figure 5 is the base sequence of the cDNA that encodes xanthosine N " * 7 methyl transferase.
  • Nucleotide ⁇ A monomeric unit of DNA or RNA consisting of a sugar moiety (pentose), a phosphate, and a nitrogenous heterocyclic base.
  • the base is linked to the sugar moiety via the glycosidic carbon (V carbon of the pentose) and that combination of base and sugar is called a nucleoside.
  • the base characterizes the nucleotide.
  • the four DNA bases are adenine ("A”), guanine (“G”), cytosine ("C”), and thymine (“T”).
  • the four RNA bases are A, G, C, and uracil ("U”).
  • DNA Sequence A linear array of nucleotides connected one to the other by phosphodiester bonds between the 3' and 5' carbons of adjacent pentoses.
  • the nucleotide triplets TTA, TTG, CTT, CTC, CTA and CTG encode for the amino acid leucine ("Leu"), TAG, TAA and TGA are translation stop signals and ATG is a translation start signal, which also encodes the amino acid methionine ("MET").
  • Polvpeptide A linear array of amino acids connected one to the other by peptide bonds between the amino and carboxy groups of adjacent amino acids.
  • Genome ⁇ The entire DNA of a cell or a virus. It includes inter alia the structural gene coding for the polypeptides of the substance, as well as promoter, transcription and translation initiation and termination sites.
  • Gene A DNA sequence which encodes through its template or messenger RNA (“mRNA”) a sequence of amino acids characteristic of a specific polypeptide.
  • mRNA messenger RNA
  • Transcription The process of producing mRNA from a gene or DNA sequence.
  • Translation ⁇ The process of producing a polypeptide from mRNA.
  • Expression The process undergone by a gene or DNA sequence to produce a polypeptide. It is a combination of transcription and translation.
  • Plasmid A nonchromosomal double-stranded DNA sequence comprising an intact "replicon" such that the plasmid is replicated in a host cell.
  • the characteristics of that organism may be changed or transformed as a result of the DNA of the plasmid.
  • a plasmid carrying the gene for tetracycline resistance (TETR) transforms a cell previously sensitive to tetracycline into one which is resistant to it.
  • a cell transformed by a plasmid is called a "transformant.”
  • Phage or Bacteriophage Bacterial virus many of which consist of DNA sequences encapsidated in a protein envelope or coat ("capsid").
  • Cloning Vehicle A plasmid, phage DNA, cosmid or other DNA sequence which is able to replicate in a host cell, characterized by one or a small number of endonuclease recognition sites at which such DNA sequences may be cut in a determinable fashion without attendant loss of an essential biological function of the DNA, e.g., replication, production of coat proteins or loss of promoter or binding sites and which contain a marker suitable for use in the identification of transformed cells, e.g., tetracycline resistance or ampicillin resistance.
  • a cloning vehicle is often called a vector.
  • Cloning The process of obtaining a population of organisms or DNA sequences derived from one such organism or sequence by asexual reproduction.
  • Recombinant DNA Molecule or Hybrid DNA - A molecule consisting of segments of DNA from different genomes which have been joined end-to-end outside of living cells and able to be maintained in living cells.
  • the strategy for producing caffeine free coffee may be generalized to other enzymes in the pathway for caffeine synthesis in coffee and other caffeine producing plants, in the presently preferred embodiment of this invention, the expression of the first unique enzyme in the pathway, xanthosine N ⁇ methyl transfersase (XMT) is suppressed. While the role of XMT in caffeine synthesis has been elucidated by radiolabeling of precursors, to date the enzyme has not been purified nor has its amino acid sequence been determined. This invention therefore includes substantially purified XMT. The invention further includes the amino acid sequence of tryptic fragments isolated from the purified XMT.
  • cDNA probes based on portions the amino acid sequence obtained from samples of the purified enzyme were synthesized and a portion of the gene was amplified using PCR.
  • the PCR products were used to screen a cDNA library synthesized from young leaf mRNA to identify transcripts encoding XMT.
  • the positive transcripts were sequenced and approximately 90% of the gene encoding XMT was obtained.
  • DNA that codes on expression for XMT are incorporated into a pBI-121 transformation vector which includes a kanamycin resistance gene. Successful incorporation of the vectar into plant cells will be monitored by acquisition of antibiotic resistance.
  • the constructs are used to transform coffee somatic embryos in tissue culture. The transformed embryos are thereafter grown into novel coffee plants that do not produce caffeine. Naturally decaffeinated coffee is prepared from roasted ground fruit from these novel plants.
  • the purity of the protein isolates was determined using SDS PAGE electrophoresis and two dimensional gel electrophoresis. Silver staining of one dimensional SDS PAGE gels indicated the presence of a doublet with the enzymatic activity of XMT, with a molecular weight of 36-37 kiloDaltons (kD) as shown in Figure 2. Each protein was further resolved with isoelectric focusing. The data indicates the presence of isozymes of XMT that may result from post translational modification of the protein; alternatively, there may be a gene family encoding XMT enzymes.
  • the cDNA corresponding to the gene encoding XMT is used to transform embryonic coffee plants.
  • the plasmid pBI-121 is used as a transforming vector.
  • the sequences corresponding to DNA that codes on expression for XMT is inserted into the plasmid in an inverted orientation adjacent to a cauliflower mosaic virus 35S promoter.
  • RNA transcribed therefrom will be complementary to mRNA that encodes the amino acid sequence of XMT.
  • Complete constructs are amplified in bacterial hosts. The hosts are disrupted and the amplified vector is attached to colloidal gold particles.
  • the gold particles with adherent vectors are inserted into coffee plant protoplasts by propelling the particles at high speed at the cells as described in U.S. patent 5,107,065. Young plants successfully transformed are identified by antibiotic resistance. The transformed plants do not produce caffeine.
  • Young leaf tissue less than 5 mm in length (equivalent to the B3 stage (Frischknecht, P.M., Ulmer-Dufek, J. and Baumann, T.W. (1986) Phvtochemistrv 25:613) were collected from trees grown at the University of Hawaii Waimanalo Research Station, Oahu, Hawaii. Leaves were immediately immersed in liquid nitrogen (liquid N2) and stored at -70°C until used. All subsequent procedures were carried out at 4°C unless otherwise stated. Leaf tissue (150 g) was macerated in a mortar and pestle under liquid N2 and, while still frozen, transferred to a pre-chilled domestic coffee grinder and ground with a small piece of dry ice for about 30 sec.
  • the powdered tissue was added to a beaker containing 1.5 L of ice cold 80% acetone, 5 mM thiourea, and 12.5 mM ⁇ -mercaptoethanol. After mixing on a magnetic stirrer for 45 min, the tissue was recovered by filtration under vacuum in a Buchner funnel containing Whatman No. 1 filter paper. The tissue was washed with 2.5 L of 80% ice cold acetone containing thiourea and ⁇ -mercaptoethanol as above, air dried for 20 min and then lyophilized for 48 hours.
  • the resulting acetone powder was homogenized in a blender with 400 mL of extraction buffer (EB) (0.1 M PIPES [pH 7.0], 0.5 mM Na 2 EDTA, 0.5 mM Na 2 EGTA, 5% ascorbic acid, 5 mM dithiothreitol [DTT], 5 mM thiourea, 12 mM L-cysteine HC1, 1% polyethylene glycol (PEG) 20,000, 0.1 mM phenylmethylsulfonyl fluoride [PMSF], and 20 g polyvinyl-polypyrrolidone [PVPP]).
  • EB extraction buffer
  • the 350 mL crude supernatant obtained was brought to 40% ammonium sulfate (AS) saturation over 30 min by the slow addition of 79.86 g AS powder while being stirred in a beaker surrounded by an ice bath.
  • AS ammonium sulfate
  • the mixture was once again transferred to 250 mL centrifuge bottles and centrifuged at 23,000xg for 30 min as above.
  • the 350 mL supernatant obtained was loaded into a 40 mL Macro-Prep (Bio-Rad) methyl hydrophobic interaction chromatography (HIC) column at the flow rate of 2.5 mL/min. All column fractions were monitored for protein using absorbance at 280 nm.
  • Macro-Prep Bio-Rad
  • HIC methyl hydrophobic interaction chromatography
  • the HIC column was washed with pre- equilibration buffer containing 1.7 M AS, 20 mM bis-tris-propane (pH 6.8), and 5 mM DTT until a baseline near zero was established. The column was then stripped with a buffer containing 10 mM tris (pH 7.0), 5 mM DTT, 1 mM MgC ⁇ . The first 15 mL out of the column was discarded and the remaining eluate (200 mL) was loaded under gravity into a
  • Cibacron blue F3GA covalently attached to the matrix.
  • the gel was pre-equilibrated with 10 mM tris (pH 7.0), 5 mM DTT, 1 mM MgCl 2 loading buffer.
  • the column was washed extensively with this loading buffer until the baseline stabilized near zero, and the bound proteins were eluted with a buffer containing 10 mM tris (pH 7.0), 5mM DTT, and 1.5 M sodium chloride (NaCl).
  • the 142 mL Affi-Gel Blue Gel column eluate was made 1.7 M AS by the slow addition of 31.8 g AS powder while being stirred for 30 min in a beaker surrounded by an ice bath.
  • the slurry was centrifuged in 250 mL centrifuge bottles at 23,000xg for 30 min as above, and the supernatant loaded into an FPLC Phenyl-Sepharose column XK 26/20
  • the 0 M AS elution buffer contained 10 mM tris (pH 7.0), 5 mM DTT, and 1 mM MgCl 2 .
  • the collection tubes contained 100 ⁇ L 0.5 M tricine buffer (pH 7.0), and 50 mM DTT to give a final concentration in 1 mL of 50 mM tricine (pH 7.0), and 5 mM DTT in 1 min fractions. This in effect stabilized the final pH conditions for the proteins eluted under slightly acidic pH from the Mono-P column.
  • the major activity for xanthosine-N'-methyltransferase in collection tubes without tricine was found in fractions 15 and 16 of the gradient eluting from the column with a pH of 5.42 and 5.35 respectively. It was important not to freeze the protein samples at any stage of the purification, as this had a substantial negative effect on the activity state of xanthosine-N'-methyltransferase.
  • the 100 ⁇ L standard assay mixture contained 50 mM tricine (pH 7.0), 1200 ⁇ M xanthosine, 5 mM DTT, 7.5 ⁇ M S-adenosyl-L-[methyl- ⁇ C]-methionine (SAM) (60mCi/mmol; DuPont NEN), and 1 mM Na 2 EDTA.
  • the reaction mixture 50 ⁇ L without enzyme was preincubated for 10 min at 25°C and the reaction was initiated by the addition of 50 ⁇ L enzyme solution and allowed to proceed at 25°C for 1 hour.
  • 7-methylxanthosine was determined by its blue fluorescence when exposed to short wavelength UV light. This region was cut out of the chromatograms and the radioactivity was determined by scintillation counting using 3 L Scinti-verse scintillation fluid (Fisher Scientific). Counting efficiency was 74.7%. Background and non-specific radiation detected in the 7-methylxanthosine region of the zero time samples were subtracted.
  • the site of methylation on the xanthine ring was identified by hydrolysis of the sugar from the methylated xanthosine reaction product and separation in 4 different chromatography systems.
  • the chromatogram was developed in n-BuOH-HOAc-H 2 0 (4:1:1).
  • the region of the chromatogram corresponding to methylated xanthosine was detected as above, cut into small pieces, placed in a sterile tube, and incubated with 35 mL of deionized water at 37°C with shaking overnight.
  • the extract was filtered through 2 layers of miracloth followed by a 0.22 ⁇ m filter and then lyophilized.
  • the dried extract was resuspended in 1.0 mL of deionized water, placed in a glass digestion vial and lyophilized.
  • the sample was resuspended in 400 ⁇ L of 1.0 M HC1 and incubated for 1 hour at 100°C.
  • the digest was lyophilized, resuspended in 400 ⁇ L of 3 mM 7-methyl- xanthine and again lyophilized.
  • the digest was resuspended in 40 ⁇ L of deionized water, and 10 ⁇ L was chromatographed in each of four different systems.
  • 1-Methylxanthine, 3- methylxanthine, 7-methylxanthine, 8-methylxanthine, 7-methylxanthosine, xanthine and xanthosine were included on each chromatogram for comparison.
  • the following chromatography systems were used; Whatman No.l paper developed in M-BUOH-HOAC- H 2 0 (4:1:1) and C8 thin layer plates (Whatman KC18F) developed in either isoamyl alcohol-H 2 0-acetonitrile (41:4:5), ethanol-H 2 0 (4:1) or tert-BuOH-HOAc-H 2 O (4:1:1).
  • Extracts obtained as above were used in single dimension (ID) SDS-PAGE minigels (main gel: 12.5% acrylamide, 0.8% methylene bisacrylamide; stacking gel:7.5% acrylamide, 0.21% methylene bisacrylamide) by mixing with Laemmli sample buffer (Laemmli, U.K., Nature 227:680 (1970)), and in two-dimensional (2D) mini IEF/SDS-PAGE by the modified method of O'Farrell et.al. (O'Farrell, P.Z., Goodman, H.M., O'Farrell P.H., Cell 12:1133 (1977)).
  • ID single dimension
  • 2D two-dimensional
  • Two-dimensional electrophoresis was made possible by precipitating proteins with 50 volumes of 100% ethanol for 1 hour and redissolving the proteins in isoelectric focusing (IEF) sample buffer containing 5% ampholines (1:1, v:v, pH 3-10:pH 5-7, LKB-Pharmacia).
  • IEF isoelectric focusing
  • the ratio of the original protein extract to the IEF sample buffer was maintained at least 1:2 to ensure that any remaining buffer constituents from the chromatography steps did not interfere with IEF.
  • Equal total protein samples ( ⁇ 20 ⁇ g) were applied to the basic end of prefocused tube gels (8.8% acrylamide, 1.6% methylene bisacrylamide) containing 5% ampholines as above. The gels were focused for 10,000V-hours plus an additional 2 hours at
  • the tube gels were prepared for SDS-PAGE by a brief H 2 0 wash followed by three washes (10 min each) in hot Laemmli sample buffer.
  • the tube gels were placed on the top of SDS-PAGE gels (main gel: 12.5% acrylamide, 0.8% methylene bisacrylamide; stacking gel:7.5% acrylamide, 0.21% methylene bisacrylamide) and held in place with 3% agarose in Laemmli sample buffer. Proteins were visualized by silver-staining.
  • ID gels the Mono-P fraction 16 which had the highest enzymic activity indicated only the presence of a doublet under silver staining ( Figure 2).
  • the molecular weights of these proteins (kD) were approximately 37.6 and 36.1 kD.
  • the tube was allowed to incubate on ice overnight, and was then centrifuged at 14,000 rpm in a microcentrifuge for 30 min at 4°C. The supernatant was removed by aspiration, and the pellet washed twice with 1 mL of 75% ethanol, each washing being followed by a centrifugation step. The pellet was dried by placing the tube in a speedvac and spinning for 1 min under vacuum. The precipitate had 20 ⁇ L of 2 x Laemmli sample buffer added to it. It was then boiled in a water bath for 5 min, and then microfuged for 1 min. When the tube temperature had cooled down to 23°C the whole amount was loaded into a single lane of a 12.5% ID gel.
  • the gel piece containing the doublet was washed 4 times with 15 mL of H 2 0 by shaking gently for 15 min to remove the acetic acid and SDS remaining from the previous steps.
  • the gel piece was diced with a razor blade to 2 mm squares, and transferred to a 1.5 mL microcentrifuge tube.
  • the gel pieces were dehydrated in a Speed- Vac for 2 hours until they did not adhere to the tube.
  • 30 ⁇ L of gel rehydration buffer (0.1 M Tris-HCl, pH 9.0, 0.05% SDS) was added, and the pH verified at 8.0 by spotting 0.5 ⁇ L on pH paper.
  • the digestion enzyme Lys-C (0.2 ug) from Achromobacter lyticus (Wako) was added, along with additional rehydration buffer to completely hydrate the gel pieces and leave a little extra buffer.
  • the mixture was allowed to incubate overnight at
  • the dried tryptic digestion products were dissolved in 25 ⁇ L of 6 M guanidine-HCl, 0.4 M tris (pH 8.2), and the pH verified by spotting 0.5 ⁇ L on pH paper.
  • One ⁇ L of 450 mM DTT was added and the digest was incubated for 45 min at 50°C. After cooling to room temperature 2 ⁇ L of 500 mM iodoacetamide was added, and incubated for a further 15 min at 23°C. At the end of this incubation 72 ⁇ L of water was added to give a final concentration of 1.5 M guanidine, and 0.1 M tris.
  • the sample was then centrifuged for 5 min at 14,000 rpm in a microcentrifuge and the supernatant was carefully removed to a new microcentrifuge tube.
  • To the precipitated pellet 25 ⁇ L of 0.1 % TFA vas added and vortexed.
  • the tube was then re- centrifuged as before, and the supernatant added to that from the previous step.
  • the cleavage fragments from the tryptic digestion were resolved from each other by capillary high pressure liquid chromatography (HPLC) in a C18 1 mm x 10 cm column, utilizing a linear gradient over 90 min of 5% solvent A (0.1% TFA) to 70% solvent B
  • the tissue was then homogenized in a glass beaker in an ice bath for 2 min at high speed in a Polytron homogenizer. Immediately after homogenization 14 mL 3 M sodium acetate (pH 4.0) was added and mixed by operating the homogenizer for an additional 1 min. The homogenate was then stored on ice for 15 min., and subsequently transferred into two 250 mL polypropylene centrifuge tubes. Centrifugation was performed in a GSA (DuPont Sorvall) rotor at 16,000xg for 10 min. The aqueous phase (top layer) was transferred to a new 250 mL polypropylene centrifuge tube and an equal volume of isopropanol was added to it.
  • GSA DuPont Sorvall
  • RNA pellet was washed with 70% ethanol and re-centrifiiged at 10,000xg for 5 min. The ethanol was decanted and the pellet dried under vacuum for 5 min. The pellet was then resuspended in 15 mL of DEPC-treated water. The RNA suspension was transferred into a sterile 40 mL screw-cap centrifuge tube and the insoluble material removed by centrifugation at 10,000xg for 5 min.
  • the supernatant was transferred to a new 40 mL screw-cap centrifuge tube and 5 mL of 8 M LiCl was added to it to give a final concentration of 2 M LiCl.
  • the tube was incubated overnight at 4°C and the RNA was recovered by centrifugation at 14,000xg for 10 min.
  • the RNA pellet was then washed with 70% ethanol, centrifiiged at 10,000xg for 5 min, and briefly dried under vacuum.
  • the pellet was resuspended in 5 mL DEPC-treated water and centrifiiged at 10,000xg for 5 min to remove insoluble material.
  • the supernatant was transferred into four sterile 1.5 mL microcentrifuge tubes and stored on ice.
  • RNA quantitation of 10 ⁇ L of the total RNA solution in a Shimadzu UV 160U spectrophotometer in a 230 to 330 nm spectrum indicated that there was 42.8 mg of RNA.
  • the tubes containing the RNA were stored at -70°C.
  • RNA preparation was enriched for poly (A + ) RNA (mRNA) using the PolyATtract II mRNA isolation system kit (Promega Corporation). A 600 ⁇ L aliquot of the total RNA equalling 5.1 mg was added into a tube of the above mentioned kit and made to 2.43 mL final volume with RNase-free water. After heating at 65°C for 10 min, 10 ⁇ L of 50 pmole/ml biotinylated oligo(dT) and 60 ⁇ L of 20x SSC (175.3 g/L NaCl, 88.2 g/L sodium citrate, pH 7.0) were added and the mixture was allowed to slowly cool to room temperature over a period of approximately 30 min.
  • the mRNA was recovered by suspending the particles in 1.0 mL RNase-free water and removing the water while the particles were captured on the side of the tube. The water was placed, 500 ⁇ L at a time, into two 1.5 mL sterile microcentrifuge tubes. After the addition of 1/10th volume of 3 M sodium acetate (50 ⁇ L per tube), the mRNA was recovered by precipitation with an equal volume of isopropanol (550 ⁇ L per tube). The tubes were stored at -20°C overnight and then centrifiiged at 14,000 rpm for 30 min at 4°C. The pellet was washed with 500 ⁇ L of 75% ice-cold ethanol and re-centrifuged.
  • the ethanol was decanted and the pellet dried briefly under vacuum.
  • the mRNA was dissolved in 60 ⁇ L of DEPC-treated nuclease-free sterile water. Quantitation was performed on 15 ⁇ L of the dissolved mRNA as described for total RNA. Approximately 9.6 ⁇ g of mRNA was recovered from 5 mg of total RNA.
  • First and second strand cDNA was synthesized using the ZAP-cDNA synthesis kit
  • the aqueous phase was removed to a new tube and re-extracted with chloroform.
  • the aqueous phase recovered as above.
  • the double- stranded cDNA was recovered by precipitation overnight at -20°C after the addition of 33.3 ⁇ L of 3M sodium acetate and 867 ⁇ L of 100% ethanol.
  • the precipitate was recovered by centrifugation in a microcentrifuge at 4°C for 60 min.
  • the precipitate was washed with 1 ⁇ L of 80% ethanol and recovered by centrifugation at room temperature at full speed in a microcentrifuge.
  • the supernatant was removed, the precipitate was dried under vacuum and dissolved in 45 ⁇ L of water.
  • Three ⁇ L of the resuspended double-stranded cDNA was removed and frozen at -20°C until analyzed by gel electrophoresis.
  • Xhol "sticky ends" were generated at the end of the cDNA corresponding to the 3' end of the mRNA by digestion of the Xhol site in the linker-primer (see above). Twenty- eight ⁇ L of Xhol buffer and 3 ⁇ L of 40 u/mLXhol were added to the cDNA and the reaction was incubated at 37°C for 1.5 hours. The cDNA with EcoRI sticky ends at the 5' end and Xhol sticky ends at the 3' end (relative to the original mRNA) were size fractionated by passage through a Sephacryl S-400 spin column as follows.
  • lOx STE (lOOmM tris (pH 7.0), 5 mM EDTA and 100 mM NaCl) was added and the cDNA was applied to the top of a 1 ⁇ L syringe containing Sephacryl S-400.
  • a 500 ml microcentrifuge tube was placed on the bottom of the syringe and the column was placed in a centrifuge tube and centrifiiged at about 400xg for 2 min.
  • Sixty ⁇ L of lOx STE was added to the top of the syringe, a new microcentrifuge tube was placed on the bottom and the column was again centrifiiged as before. This process was repeated until six fractions had been collected.
  • each fraction was electrophoresed on a 1% agarose gel to determine the size distribution of the cDNA in each fraction.
  • the remainder of each fraction was extracted with an equal volume of phenolxhloroform and then chloroform as described above and then precipitated by the addition of 2 volumes of 100% ethanol.
  • the cDNA was recovered by centrifugation at 14,000 rpm at 4°C for 60 min in a microcentrofuge.
  • the cDNA was washed with 200 ⁇ L of 80% ethanol as described above and dried.
  • the cDNA was dissolved in 5 ⁇ L of water and 0.5 ⁇ L was removed to deter ine the cDNA concentration by fluorography using the Hoefer TKO 100 DNA Fluorometer. The remaining 4.5 mL of fraction 1, containing the largest cDNA molecules, contained about 304 ng of cDNA.
  • Fraction 1 cDNA (2.9 Ml) was added to 0.54 ⁇ L of 10 x ligation buffer, 0.5 ⁇ L 10 mM ATP,
  • Packaging was carried out at room temperature. After 2 hours, 500 ⁇ L of SM buffer (0.01 M tris-HCL pH 7.5, 0.01 M MgCl 2 0.1 mM Na 2 EDTA) and 20 ⁇ L of chloroform was added to the packaging reaction, the debris was removed by a short centrifugation in a microcentrifuge and the packaged phages were stored at 4°C until used.
  • SM buffer 0.01 M tris-HCL pH 7.5, 0.01 M M MgCl 2 0.1 mM Na 2 EDTA
  • One ⁇ L of the 500 ⁇ L primary library was mixed with 9 ⁇ L of SM buffer for a 1/10 dilution.
  • the infected cells were then mixed with 2.5 mL of 48°C top agar containing 15 ⁇ L of 0.5 M IPTG, and 50 ⁇ L of 250 mg/ml X-gal and plated on 100x15 mm NZY plates (5 g/L NaCl, 2 g/L MgS0 4 .7H 0, 5 g/L yeast extract, 10 g/L NZ amine [pH
  • the SM buffer was collected with a sterile pipette and stored in a sterile 250 mL centrifuge tube. Each plate was washed with about 4 mL of fresh SM buffer which was added to the previously collected material. Chloroform, to a final volume of 5%, was added to the amplified library. The library was then incubated at room temperature for 15 min and then centrifiiged at 2,000xg for 10 min to remove cell debris. The supernatant (114.5 mL) was recovered and then transferred to a sterile polypropylene bottle. Chloroform was added to a final volume of 0.3% and the amplified library was stored at 4°C.
  • One ⁇ L of a 10" ⁇ dilution of the amplified library in SM buffer contained 192 recombinant plaques when plated as described above.
  • To these cells 6.5 mL of 48°C top agar was added and the library was plated on 150x15 mm NZY plates. Four such plates representing 200,000 recombinant plaques, were prepared and incubated at 37°C overnight. The plates were then chilled for 4 hours at 4°C, and then used for DNA screening of the library.
  • PCR conditions were 94°C for 4 min [1 cycle]; 94°C for 1 min, 43 °C for 1 min, 72°C for 1 min [35 cycles]; 72°C for 5 min [1 cycle]).
  • Reactions were done in 500 ⁇ L sterile microcentrifuge tubes using a Perkin Elmer DNA thermal cycler 480. Only the primer combination 1 and 6 resulted in a single product at an annealing temperature of 43°C. The product was measured by agarose gel electrophoresis using SeaPlaque agarose (FMC) to be approximately 750 base pairs. A commercially available 100 bp ladder was used as a size marker (Promega Corporation).
  • the 750 bp fragment obtained using primers 1 and 6 (Fig.4) in a 50 ⁇ L PCR reaction had 50 ⁇ L of chloroform, and 100 ⁇ L of sterile water added to it. The mixture was vortexed and then centrifiiged in a microcentrifuge at 14,000 rpm for 2 min. The top aqueous layer containing the DNA was removed and placed in a sterile tube. Ethidium-bromide plate quantitation indicated the presence of about 5 ng of about PCR amplfied DNA/ ⁇ L.
  • the PCR product was then ligated into a TA Cloning Kit pCR II vector (Invitrogen Corporation) in a 10 ⁇ L ligation reaction containing 1 ⁇ L 10 x ligation buffer, 2 ⁇ L pCR II vector (25 ng/ ⁇ L), 3 ⁇ L fresh PCR product (5 ng/ ⁇ L), 1 ⁇ L T4 DNA Ligase, and 3 ⁇ L of sterile water.
  • the ligation reaction was incubated at a 14°C overnight.
  • the ligation reactions were centrifiiged at 14,000 rpm for 2 min and placed on ice. To a freshly thawed vial of E.
  • coli XLl-Blue competent cells 2 ⁇ L of 0.5 M a-mercaptoethanol was added and mixed gently with the pipette tip. Two ⁇ L of the ligation reaction was pipetted into the cells and they were stirred gently with the pipette tip to mix. The vial was then incubated on ice for 30 minutes and heat shocked for exactly 30 seconds in a 42°C heat-block. The vial was placed on ice.
  • sterile SOC medium (20 g/L tryptone, 5 g L yeast extract, 0.5 g L NaCl, 10 mL/L 250 mM KC1, 10 mL/L MgCl 2 , 20 mL/L 1 M glucose, [pH 7.0]) was added to it.
  • the vial was subsequently shaken at 225 rpm in a rotary shaker for 1 hour and then the placed on ice.
  • the transformed cells were plated by pipetting 50 ⁇ L and/or 200 ⁇ L from the cell suspension onto one of two LB plates (10 g/L tryptone, 5 g/L yeast extract, 10 g/L NaCl, 15 g/L Difco agar, pH 7.5) containing 50 ⁇ g/mL ampicillin and 40 ⁇ g/mL X-Gal.
  • the plates were incubated at 37°C for 20 hours and then moved to 4°C for 3 hours to allow color development.
  • Six white transformant colonies were analyzed for the presence and orientation of the PCR fragment.
  • Each of the transformant colonies was grown in 5 mL sterile terrific broth (12 g/L tryptone, 24 g/L yeast extract, 4 mL/L glycerol, 100 mL/L lOx TB phosphate [0.17 M KH 2 P04, 0.72 M K 2 HP ⁇ 4]) supplemented with 50 ⁇ g/mL ampicillin.
  • the tubes were incubated overnight in a rotary shaker at 37°C. Three mL of each colony was transferred to a
  • the tubes were centrifiiged at 14,000 rpm at 4°C for 30 min, and the pellet washed with 75% ethanol and dried for 1 min in a speed-vac.
  • the DNA was resuspended in 50 ⁇ L of sterile H 2 0 containing 1 ⁇ L of 5 mg/mL RNase A.
  • a reaction mixture of 25 ⁇ L was prepared by adding 15 ⁇ L of plasmid mini-prep DNA as obtained above, 2.5 ⁇ L of buffer H (90 mM tris-HCl [pH 7.5], 10 mM MgCl 2 , 50 mM NaCl), 1 ⁇ L of EcoRI (8-12 u/ ⁇ L), and 6.5 ⁇ L of sterile H 2 0.
  • the mixture was incubated in a shaking water bath at 37°C for 1 hour, and then boiled in a water bath for 1 min.
  • the tubes were centrifiiged at 14,000 rpm for 15 seconds and then allowed to cool down to room temperature.
  • the original bacterial colony corresponding to the plasmid with the 750bp xanthosine-N'- methyl transferase PCR product was inoculated into a 250 mL Erlenmayer flask containing 50 mL of sterile LB media (10 g/L tryptone, 5 g/L yeast extract, 10 g/L NaCl, pH 7.5) supplemented with 50 ⁇ g/mL ampicillin. The flask was incubated in a rotary shaker at 30°C overnight. In a 1.5 mL microcentrifuge tube 18 mL of the resulting cell media was concentrated by centrifugation as above.
  • Plasmid DNA was purified using the QIAGEN plasmid mini kit procedure (Qiagen Inc.). The washed bacterial pellet was resuspended in 0.3 mL of buffer PI which contains the supplied RNase. To this 0.3 mL of alkaline lysis buffer P2 was added, mixed gently by flicking the tube and incubated for no longer than 5 min at room temperature. Next 0.3 mL of chilled buffer P3 was added and mixed by inverting the tube 6 times. After 10 min on ice the extract was centrifiiged 14,000 rpm for 15 min in a microcentrifuge.
  • the supernatant was removed and applied to a QIAGEN-tip 20 that was previously equilibrated by the application of 1 mL QBT buffer by gravity flow.
  • the applied cell extract supernatant was also allowed to enter the resin of the column by gravity flow.
  • the QIAGEN-tip 20 was washed 4 times with one mL buffer QC.
  • the DNA was eluted by washing the QIAGEN-tip 20 with 0.8 mL buffer QF and precipitated by the addition of 0.7 volumes (560 ⁇ L) of room temperature isopropanol. The tube was immediately centrifiiged at 14,000 rpm for 30 min and the supernatant carefully removed.
  • the precipitated DNA was washed with 1 mL of ice-cold 70% ethanol, centrifiiged as above, and air dried for 5 min.
  • the DNA was resuspended in 100 ⁇ L of sterile H 2 0. UV spectrophotometry, as described above, on 1 ⁇ L of the DNA resuspension indicated that there was 55 ⁇ g of purified recombinant pCRII plasmid DNA per 100 ⁇ L.
  • a random primed probe was systhesized from 30 ng (3 ⁇ L) of the purified DNA. Three ⁇ L of the DNA was added to 27 ⁇ L of sterile water and the DNA was denatured by heating in a boiling water bath. To this the Promega Corporations Prime-a-Gene kit constituents (10 ⁇ L 5x labeling buffer, 2 ⁇ L of unlabeled dNTP's [20 ⁇ M each dCTP, dGTP,
  • 32 P]dATP 50 ⁇ Ci, 3,000 Ci/mmole; DuPont NEN
  • 50 ⁇ Ci, 3,000 Ci/mmole 50 ⁇ L
  • the reaction was terminated by the addition of 2 ⁇ L 0.5 M Na 2 EDTA (20 mM final concentration) and heated for 2 min in a boiling water bath.
  • the four 150x15 mm NZY plates that had approximately 50,000 recombinant clones per plate were chilled to 4°C (see above for plating and growth conditions), and the recombinant plaques lifted by first presoaking 132 mm Magna nylon transfer membranes
  • DNA was cross-linked to the membranes by exposure to 12,000 ⁇ Joules of UV using a UV Stratalinker 1800 (Stratagene Corporation).
  • the four membranes were prehybridized at 65°C for 2 hours in 100 mL 6x SSPE (52.2 g/L NaCl, 8.3 g/L NaH 2 P0 .H 2 0, 2.2 g/L Na 2 EDTA,
  • Hybridization was carried out at 65°C for 12 hours in 10 mL of 6x SSPE, 0.5% SDS,
  • the membranes were subjected to two more 100 mL washes for 30 min with 65°C, 0.2x SSC, 0.5% SDS, and then rapped in a cellophane envelope and exposed to pre-flashed Fuji RXQCU X" ra y film at -70°C for 24 hours. Fifteen positive clones were observed. These plaques were picked and placed in 1 mL SM buffer containing 20 ⁇ L chloroform (phage stock). Of these, 11 were processed to secondary or tertiary screening until single individual plaques were obtained.
  • the sizes of the putative xanthosine-N ⁇ -methyltransferase cDNA clones were determined by polymerase chain reaction using primers homologous to the T3 and T7 promoters that are present in the cloning vector and that flank the cDNA insertion site. Conditions for polymerase chain reaction were as described above except that the cycle was
  • the 200 ⁇ L cells were plated on 100x15 mm NZY agar plates containing 50 ⁇ g/mL ampicillin. The plates were incubated overnight at 37°C until colonies appeared. A single colony was inoculated into 10 mL of sterile LB broth containing 50 ⁇ g/mL ampicillin and grown overnight at 37°C with shaking. The 10 mL of cell culture was concentrated in a 1.5 mL sterile microcentrifuge tube and the pelleted cells subjected to QIAGEN plasmid purification as described previously. The purified plasmid DNA was resuspended in 50 ⁇ L of sterile H 2 0.
  • DNA automated sequencing reactions were performed by mixing 8 ⁇ L of this DNA sample (0.8 ⁇ g) with 4 ⁇ L of either T3 or T7 sequencing primers (0.8 pmol/ ⁇ L). The remainder of the process was as previously described. Each sequencing reaction gave aproximately 350 bases of sequence. The sequence is shown in Figure 5. Thre amino acid sequence of xanthosine- N ⁇ -methyl transferase as predicted from the base sequence of the cDNA is shown in Figure 6.

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Abstract

L'invention concerne des protéines purifiées, des séquences d'ADN qui codent pour ces protéines lors de l'expression et des molécules d'ADN recombinées, y compris des hôtes qui ont été transformés par ces molécules, et qui servent à la transformation de plants de café de façon à supprimer l'expression de caféine. Les séquences d'ADN et les molécules d'ADN recombinées sont caractérisées en ce qu'elles codent pour une enzyme lors de l'expression dans la voie de la synthèse de la caféine dans le café. L'invention a également pour objet les plants de café transformés par des molécules d'ADN qui codent, lors de la transcription, pour l'ARNm antisens de l'ARNm codant pour au moins une enzyme lors de l'expression sur la voie de la biosynthèse de la caféine.
PCT/US1998/005557 1997-03-24 1998-03-20 Proteines purifiees, sequences d'adn recombinees, et procedes de fabrication de boissons decafeinees WO1998042848A1 (fr)

Priority Applications (2)

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PCT/US1998/005557 WO1998042848A1 (fr) 1997-03-24 1998-03-20 Proteines purifiees, sequences d'adn recombinees, et procedes de fabrication de boissons decafeinees
AU67668/98A AU6766898A (en) 1997-03-24 1998-03-20 Purified proteins, recombinant dna sequences and processes for producing caffeine free beverages

Applications Claiming Priority (3)

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AUPCT/US97/04982 1997-03-24
PCT/US1997/004982 WO1997035960A1 (fr) 1996-03-26 1997-03-24 Proteines purifiees, sequences d'adn recombinees et procedes de fabrication de boissons sans cafeine
PCT/US1998/005557 WO1998042848A1 (fr) 1997-03-24 1998-03-20 Proteines purifiees, sequences d'adn recombinees, et procedes de fabrication de boissons decafeinees

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12275939B2 (en) 2017-09-19 2025-04-15 Tropic Biosciences UK Limited Modifying the specificity of plant non-coding RNA molecules for silencing gene expression

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Publication number Priority date Publication date Assignee Title
EP0240208A2 (fr) * 1986-03-28 1987-10-07 Calgene, Inc. Réglage anti-sens d'expression de gènes dans les cellules végétales
US5334529A (en) * 1989-06-27 1994-08-02 Escagenetics Corporation Stably transformed coffee plant cells and plantlets
WO1997035960A1 (fr) * 1996-03-26 1997-10-02 University Of Hawaii Proteines purifiees, sequences d'adn recombinees et procedes de fabrication de boissons sans cafeine

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
EP0240208A2 (fr) * 1986-03-28 1987-10-07 Calgene, Inc. Réglage anti-sens d'expression de gènes dans les cellules végétales
US5334529A (en) * 1989-06-27 1994-08-02 Escagenetics Corporation Stably transformed coffee plant cells and plantlets
WO1997035960A1 (fr) * 1996-03-26 1997-10-02 University Of Hawaii Proteines purifiees, sequences d'adn recombinees et procedes de fabrication de boissons sans cafeine

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Title
CHEMICAL ABSTRACTS, vol. 121, no. 3, 18 July 1994, Columbus, Ohio, US; abstract no. 28055, SPIRAL, J. ET AL: "Development of a transformation method for coffee and regeneration of transgenic coffee plantlets" XP002071642 *
COLLOQ. SCI. INT. CAFE, [C. R.] (1993), 15TH(VOL. 1), 115-22 CODEN: CICRD8 *
KATO, M. ET AL: "Caffeine biosynthesis in young leaves of Camellia sinensis: in vitro studies on N-methyltransferase activity involved in the conversion of xanthosine to caffeine", PHYSIOLOGIA PLANTARUM, (1996) VOL. 98, NO. 3, PP. 629-636. 18 REF. ISSN: 0031-9317, XP002071639 *
SCHULTHESS, B.H., ET AL.: "Caffeine biosynthesis starts with the metabolically channelled formation of 7-methyl-XMP-a new hypothesis", PHYTOCHEMISTRY, vol. 41, no. 1, 1996, pages 169 - 175, XP002071640 *
SUZUKI, T., ET AL.: "Purine and purine alkaloid metabolism in Camellia and Coffea plants", PHYTOCHEMISTRY, vol. 31, no. 8, 1992, pages 2575 - 2584, XP002071641 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12275939B2 (en) 2017-09-19 2025-04-15 Tropic Biosciences UK Limited Modifying the specificity of plant non-coding RNA molecules for silencing gene expression

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