Characterization of a family 54 α-<Emphasis Type="SmallCaps">l</Emphasis>-arabinofuranosidase from <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis>

A glycosyl hydrolase family 54 (GH54) α-l-arabinofuranosidase gene (abfA) of Aureobasidium pullulans was amplified by polymerase chain reaction from genomic DNA and a 498-amino-acid open reading frame deduced from the DNA sequence. Modeling of the highly conserved A. pullulans AbfA protein sequence on the crystal structure of Aspergillus kawachii AkabfB showed that the catalytic amino acid arrangement and overall structure were highly similar including the N-terminal catalytic and C-terminal arabinose binding domains. The abfA gene was expressed in Saccharomyces cerevisiae, and the heterologous enzyme was purified. The protein was monomeric, migrating at 49 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and eluting at 36 kDa upon gel filtration. AbfA showed maximal activity at 55°C and between pH 3.5 and pH 4. The enzyme had a K _m value for p-nitrophenyl-α-l-arabinofuranoside of 3.7 mM and a V _max of 34.8 μmol min⁻¹ mg protein⁻¹. Arabinose acted as a noncompetitive inhibitor with a K _i of 38.4 mM. The enzyme released arabinose from maize fiber, oat spelt arabinoxylan, and wheat arabinoxylan, but not from larch wood arabinogalactan or α-1,5-debranched arabinan. AbfA displayed low activity against α-1,5-l-arabino-oligosaccharides. The enzyme acted synergistically with endo-β-1,4-xylanase in the breakdown of wheat arabinoxylan. Binding of AbfA to xylan from several sources confirmed the presence of a functional carbohydrate-binding module. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Purification and Characterization of a Novel β-<Emphasis Type="SmallCaps">d</Emphasis>-Galactosides-Specific Lectin from <Emphasis Type="Italic">Clitoria ternatea</Emphasis>

A lectin present in seeds of Clitoria ternatea agglutinated trypsin-treated human B erythrocytes. The sugar specificity assay indicated that lectin belongs to Gal/Gal NAc-specific group. Hence the lectin, designated C. ternatea agglutinin (CTA), was purified by the combination of acetic acid precipitation, salt fractionation and affinity chromatography. HPLC gel filtration, SDS-polyacrylamide gel electrophoresis and mass spectrometry indicated that the native lectin is composed of two identical subunits of molecular weight 34.7 kDa associated by non covalent bonds. The N-terminal sequence of CTA shared homology with Glycine max and Pisum sativum. Complete sequence was also found to be homologous to S-64 protein of Glycine max, suggesting that CTA probably exhibits both hemagglutination and probably sugar uptake activity. The carbohydrate binding specificity of the lectin was investigated by quantitative turbidity measurements, and percent inhibition assays. Based on these assays, we conclude that CTA binds β-d-galactosides, and also may has an extended specificity towards non-reducing terminal Neu5Acα2,6Gal.     

Production of pure β-glucan by <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> after pullulan synthetase gene disruption

By disruption of the pullulan synthetase gene (pul) of Aureobasidium pullulans IMS822 KCTC11179BP, we constructed a mutant strain, A. pullulans NP1221, which produced a pure β-glucan exopolysaccharide. The mutant NP1221 was white, whereas the wild-type strain produced a black dye. When we compared fermentation kinetics between wide-type and mutant strains, the mutant NP1221 did not produce pullulan. Substrate uptake rate and β-glucan production were similar in both strains. However, the biomass yield of mutant NP1221 was 2.3-fold (9.2 g l⁻¹) greater than that of wild-type.     

The α-<Emphasis Type="SmallCaps">l</Emphasis>-fucosidase from <Emphasis Type="Italic">Sulfolobus solfataricus</Emphasis>

Glycoside hydrolases form hyperthermophilic archaea are interesting model systems for the study of catalysis at high temperatures and, at the moment, their detailed enzymological characterization is the only approach to define their role in vivo. Family 29 of glycoside hydrolases classification groups α-l-fucosidases involved in a variety of biological events in Bacteria and Eukarya. In Archaea the first α-l-fucosidase was identified in Sulfolobus solfataricus as interrupted gene expressed by programmed −1 frameshifting. In this review, we describe the identification of the catalytic residues of the archaeal enzyme, by means of the chemical rescue strategy. The intrinsic stability of the hyperthermophilic enzyme allowed the use of this method, which resulted of general applicability for β and α glycoside hydrolases. In addition, the presence in the active site of the archaeal enzyme of a triad of catalytic residues is a rather uncommon feature among the glycoside hydrolases and suggested that in family 29 slightly different catalytic machineries coexist.     

Characterization and enzymatic hydrolysis of hydrothermally treated β-1,3–1,6-glucan from <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis>

The chemical structure of hydrothermally treated β-1,3–1,6-glucan from Aureobasidium pullulans was characterized using techniques such as gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR). The chemical shifts of anomeric carbons observed in the ¹³C-NMR spectra suggested the presence of single flexible chains of polysaccharide in the sample. β-1,3–1,6-Glucan from A. pullulans became water-soluble, with an average molecular weight of 128,000 Da after hydrothermal treatment, and the solubility in water was approximately 10% (w/w). Sample (3% w/v) was completely hydrolyzed to glucose by enzymatic reaction with Lysing enzymes from Trichoderma harzianum. Gentiobiose (Glcβ1 → 6Glc) and glucose were released as products during the reaction, and the maximum yield of gentiobiose was approximately 70% (w/w). The molar ratio of gentiobiose to glucose after 1 h reaction suggested that the sample is likely highly branched. Sample (3% w/v) was also hydrolyzed to glucose by Uskizyme from Trichoderma sp., indicating that it is very sensitive to enzymatic hydrolysis.     

High-level production of poly (β-<Emphasis Type="SmallCaps">l</Emphasis>-malic acid) with a new isolated <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> strain

Poly (β-l-malic acid) (PMLA) is a water-soluble polyester with many attractive properties in chemical industry and medicine development. However, the low titer of PMLA in the available producer strains limits further industrialization efforts and restricts its many potential applications. In order to solve this problem, a new strain with the distinguished high productivity of PMLA was isolated from fresh plants samples. It was characterized as the candidate of Aureobasidium pullulans based on the morphology and phylogenetic analyses of the internal transcribed spacer sequences. After the optimization of culture conditions, the highest PMLA concentration (62.27 g l⁻¹) could be achieved in the shake flask scale. In addition, the contribution of the carbon flux to exopolysaccharide (EPS) and PMLA could be regulated by the addition of CaCO₃ in the medium. This high-level fermentation process was further scaled up in the 10 l benchtop fermentor with a high PMLA concentration (57.2 g l⁻¹) and productivity (0.35 g l⁻¹ h⁻¹), which are the highest level in all the literature. Finally, the suitable acid hydrolysis conditions of PMLA were also investigated with regard to the production of l-malic acid, and the kinetics of PMLA acid hydrolysis was modeled to simulate the whole degradation process. The present work paved the road to produce this multifunctional biomaterial (PMLA) at industrial scale and promised one alternative method to produce l-malic acid in the future.     

Endogeneous β-<Emphasis Type="SmallCaps">d</Emphasis>-xylosidase and α-<Emphasis Type="SmallCaps">l</Emphasis>-arabinofuranosidase activity in flax seed mucilage

Flax seed mucilage (FM) contains a mixture of highly doubly substituted arabinoxylan as well as rhamnogalacturonan I with unusual side group substitutions. Treatment of FM with a GH11 Bacillus subtilis XynA endo 1,4-β-xylanase (BsX) gave limited formation of reducing ends but when BsX and FM were incubated together on different wheat arabinoxylan substrates and birchwood xylan, significant amounts of xylose were released. Moreover, arabinose was released from both water-extractable and water-unextractable wheat arabinoxylan. Since no xylose or arabinose was released by BsX addition alone on these substrates, nor without FM or BsX addition, the results indicate the presence of endogenous β-d-xylosidase and α-l-arabinofuranosidase activities in FM. FM also exhibited activity on both p-nitrophenyl α-l-arabinofuranoside (pNPA) and p-nitrophenyl β-d-xylopyranoside (pNPX). Based on K _M values, the FM enzyme activities had a higher affinity for pNPX (K _M 2 mM) than for pNPA (K _M 20 mM).     

Production of fructooligosaccharides by crude enzyme preparations of β-fructofuranosidase from <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis>

Fructooligosaccharides (FOS) were produced from sucrose by using crude enzyme preparations of β-fructofuranosidases (FFases) obtained from sucrose-cultured cells of Aureobasidium pullulans DSM 2404. When the preparation mainly consisted of FFase I, that has high transfructosylating activity, the FOS yield was 62%. When the reaction was carried out with additional commercial glucose isomerase (GI) at an activity ratio of FFase and GI of 1:2, the maximum FOS yield reached 69%. This value was higher than those obtained previously using other Aureobasidium spp. (53–59%).     

Identification of aryl-phospho-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucosidases in<Emphasis Type="Italic"> Bacillus subtilis</Emphasis>

Four aryl-phospho--d-glucosidases were identified in Bacillus subtilis by using 4-methylumbelliferyl-phospho--d-glucopyranoside as a substrate. Two of these enzymes are the products of the bglA and bglH genes, previously suggested to encode aryl-phospho--d-glucosidases, while the other enzymes are encoded by the yckE and ydhP genes. Together, these four genes account for >99.9% of the glucosidase activity in B. subtilis on aryl-phospho--d-glucosides. yckE was expressed at a low and constant level during growth, sporulation, and spore germination, and was not induced by aryl--d-glucosides. ydhP was also not induced by aryl--d-glucosides. However, while ydhP was expressed at only a very low level in exponential-phase cells and germinating spores, this gene was expressed at a higher levels upon entry into the stationary phase of growth. Strains lacking yckE or ydhP exhibited no defects in growth, sporulation, or spore germination or in growth on aryl--d-glucosides. However, a strain lacking bglA, bglH and yckE grew poorly if at all on aryl--d-glucosides as the sole carbon source.Abbreviations MU 4-Methylumbelliferone - MUG 4-Methylumbelliferyl--d-glucopyranoside - MUGal 4-Methylumbelliferyl--d-galactopyranoside - MUG-P 4-Methylumbelliferyl--d-glucopyranoside-6-phosphate     

Cyclitols affect accumulation of α-<Emphasis Type="SmallCaps">d</Emphasis>-galactosides in developing <Emphasis Type="Italic">Vicia</Emphasis> seeds

The mechanism preferentially regulating accumulation of raffinose family oligosaccharides (RFOs) or galactosyl cyclitols in legume seeds still remains unknown. The broad range of raffinose family oligosaccharides and galactosyl pinitols in the composition of seeds of Vicia genus gives researchers an exceptional opportunity for investigations on relationships in biosynthesis of both types of α-d-galactosides. Feeding explants of Vicia species radically different in the composition of RFOs and galactosyl pinitols with basic galactose acceptors, sucrose (for RFOs) or cyclitols (for galactosyl cyclitols) can be a helpful method for assessment of their regulatory role in accumulation of α-d-galactosides in seeds. Garden vetch (Vicia sativa L.) seeds, naturally accumulating RFOs, demonstrated an ability to take up and use exogenously applied d-pinitol and d-chiro-inositol for synthesis of their mono-, di- and tri-galactosides. Together with the accumulation of new galactosides, the concentration of RFOs decreased. In fine-leaved (Vicia tenuifolia Roth.) vetch seeds such a remarkably high concentration of galactosyl pinitols (GPs) was discovered that they nearly replaced RFOs, which is unique among legumes. If the accumulation of both types of galactosides is correlated with concentration of galactose acceptors, elevated levels of sucrose or myo-inositol should promote accumulation of RFOs, instead of GPs. Unexpectedly, feeding fine-leaved vetch raceme explants with myo-inositol or sucrose promoted accumulation of GPs, but not of RFOs. Our comparison of accumulation and biosynthesis of both types of galactosides (RFOs and GPs) throughout development and maturation of seeds from fine-leaved vetch has indicated that preferential accumulation of GPs is associated with the drying of seeds during maturation. Different patterns in activities of enzymes engaged in RFOs’ biosynthetic pathway and galactosyltransferases involved in biosynthesis of GPs indicated that distinct forms of enzymes can operate in both pathways. The feeding of explants with d-chiro-inositol causes accumulation of fagopyritols B1 in seeds of both Vicia species, which suggests presence of the same or a similar form of galactinol synthase. Accumulation of fagopyritols in fine-leaved vetch seeds did not affect accumulation of RFOs or galactosyl pinitols.     

Growth inhibitory activity of ABA-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucopyranosyl ester and ABA-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucosidase

Exogenously applied ABA-β-d-glucopyranosyl ester (ABA-GE) inhibited shoot growth of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), Digitaria sanguinalis L., timothy (Pheleum pratense L.) and ryegrass (Lolium multiflorum Lam.) seedlings at concentrations greater than 0.1 μM. The growth inhibitory activity of ABA-GE on these shoots was 26–40% of that of (+)-ABA. ABA-β-d-glucosidase activities in these seedlings were 11–31 nmol mg⁻¹ protein min⁻¹. These results suggests that exogenously applied ABA-GE may be absorbed by plant roots and hydrolyzed by ABA-β-d-glucosidase, and liberated free ABA may induce the growth inhibition in these plants. Thus, although ABA-GE had been thought to be physiologically inactive ABA conjugate, ABA-GE may have important physiological functions rather than an inactive conjugated ABA form.     

Investigation of the active site of the extracellular β-<Emphasis Type="SmallCaps">D</Emphasis>-glucosidase from <Emphasis Type="Italic">Aspergillus carbonarius</Emphasis>

Summary The catalytic amino acid residues of the extracellular β-D-glucosidase (β-D-glucoside glucohydrolase, EC 3.2.1.21) from Aspergillus carbonarius were investigated. The pH dependence curves gave apparent pK values of 2.8 and 5.93 for the free enzyme, and 2.24 and 6.14 for the enzyme–substrate complex using p-nitrophenyl-β-D-glucoside as substrate. Carbodiimide- and Woodward reagent K-mediated chemical modifications suggested that a carboxylate residue, located in the active centre, was fundamental in the catalysis. The pH dependence of inactivation revealed the involvement of a group with pK value of 4.61 in the modification reaction, proving that a carboxylate residue was modified. The A. carbonarius β-glucosidase was irreversibly inactivated by N-bromoacetyl-β-D-glucopyranosylamine. The active site specificity of the inactivation was proved by using the competitive inhibitor p-nitrophenyl-1-thio-β-D-glucopyranoside. pH Dependence studies of inactivation revealed that modification by N-bromoacetyl-β-D-glucopyranosylamine could be directed toward the carboxylate group acting as the catalytic nucleophile, as in the case of the carbodiimide and Woodward reagent K modifications.     

Hydrosoluble Antioxidants by Enzymatic Glucosylation of a Vitamin E Derivative Using Marine α-<Emphasis Type="SmallCaps">d</Emphasis>-Glucosidase from <Emphasis Type="Italic">Aplysia fasciata</Emphasis>

Relevant examples of polyglycosylating exo-glycosidases were reported among enzymes of marine origin (Aplysia fasciata, Geobacillus, and Pecten maximus). Herein we describe the enzymatic polyglucosylation of a chromane-methanol (2-hydroxymethyl-2,5,7,8-tetramethylchroman-6-ol) performed by using the α-d-glucosidase from the sea hare Aplysia fasciata. New di-, tri-, and tetrasaccharide derivatives were synthesized and their antioxidant activities were evaluated by DPPH test. High enzymatic substrate conversion was assessed by NMR spectroscopy, and the products were easily purified. These findings suggest that the proposed procedure is an effective process both for the molecular diversity of products and for the peculiar stereochemistry of the enzyme. At the beginning of the enzymatic reaction, only (S)-diastereomer of the monoglucoside was obtained. The isomaltoside was the most abundant disaccharide obtained and showed a radical scavenging activity similar to that of the chromane-methanol. The disaccharide can be considered a new hydrosoluble antioxidant agent useful for various technological applications (cosmetics, food industry, etc.). A relationship between the interglycosidic linkage present in disaccharides and trisaccharides and their scavenging activity was also pointed out.     

Purification and biochemical properties of a thermostable xylose-tolerant β-<Emphasis Type="SmallCaps">D</Emphasis>-xylosidase from <Emphasis Type="Italic">Scytalidium thermophilum</Emphasis>

The thermophilic fungus Scytalidium thermophilum produced large amounts of periplasmic -D-xylosidase activity when grown on xylan as carbon source. The presence of glucose in the fresh culture medium drastically reduced the level of -D-xylosidase activity, while cycloheximide prevented induction of the enzyme by xylan. The mycelial -xylosidase induced by xylan was purified using a procedure that included heating at 50°C, ammonium sulfate fractioning (30–75%), and chromatography on Sephadex G-100 and DEAE-Sephadex A-50. The purified -D-xylosidase is a monomer with an estimated molecular mass of 45 kDa (SDS-PAGE) or 38 kDa (gel filtration). The enzyme is a neutral protein (pI 7.1), with a carbohydrate content of 12% and optima of temperature and pH of 60°C and 5.0, respectively. -D-Xylosidase activity is strongly stimulated and protected against heat inactivation by calcium ions. In the absence of substrate, the enzyme is stable for 1 h at 60°C and has half-lives of 11 and 30 min at 65°C in the absence or presence of calcium, respectively. The purified -D-xylosidase hydrolyzed p-nitrophenol--D-xylopyranoside and p-nitrophenol--D-glucopyranoside, exhibiting apparent K_m and V_max values of 1.3 mM, 88 mol min^–1 protein^–1 and 0.5 mM, 20 mol min^–1 protein^–1, respectively. The purified enzyme hydrolyzed xylobiose, xylotriose, and xylotetraose, and is therefore a true -D-xylosidase. Enzyme activity was completely insensitive to xylose, which inhibits most -xylosidases, at concentrations up to 200 mM. Its thermal stability and high xylose tolerance qualify this enzyme for industrial applications. The high tolerance of S. thermophilum -xylosidase to xylose inhibition is a positive characteristic that distinguishes this enzyme from all others described in the literature.     

Engineering lower inhibitor affinities in β-<Emphasis Type="SmallCaps">d</Emphasis>-xylosidase of <Emphasis Type="Italic">Selenomonas ruminantium</Emphasis> by site-directed mutagenesis of Trp145

β-d-Xylosidase/α-l-arabinofuranosidase from Selenomonas ruminantium is the most active enzyme reported for catalyzing hydrolysis of 1,4-β-d-xylooligosaccharides to d-xylose. One property that could use improvement is its relatively high affinities for d-glucose and d-xylose (K _i ~ 10 mM), which would impede its performance as a catalyst in the saccharification of lignocellulosic biomass for the production of biofuels and other value-added products. Previously, we discovered that the W145G variant expresses K _i ^d-glucose and K _i ^d-xylose twofold and threefold those of the wild-type enzyme. However, in comparison to the wild type, the variant expresses 11% lower k _cat ^d-xylobiose and much lower stabilities to temperature and pH. Here, we performed saturation mutagenesis of W145 and discovered that the variants express K _i values that are 1.5–2.7-fold (d-glucose) and 1.9–4.6-fold (d-xylose) those of wild-type enzyme. W145F, W145L, and W145Y express good stability and, respectively, 11, 6, and 1% higher k _cat ^d-xylobiose than that of the wild type. At 0.1 M d-xylobiose and 0.1 M d-xylose, kinetic parameters indicate that W145F, W145L, and W145Y catalytic activities are respectively 46, 71, and 48% greater than that of the wild-type enzyme.     

Glutamate production from β-glucan using endoglucanase-secreting <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

We demonstrate glutamate production from β-glucan using endoglucanase (EG)-expressing Corynebacterium glutamicum. The signal sequence torA derived from Escherichia coli K12, which belongs to the Tat pathway, was suitable for secreting EG of Clostridium thermocellum using C. glutamicum as a host. Using the torA signal sequence, endoglucanase from Clostridium cellulovorans 743B was successfully expressed, and the secreted EG produced 123 mg of reducing sugar from 5 g of β-glucan at 30 °C for 72 h, which is the optimal condition for C. glutamicum growth. Subsequently, glutamate fermentation from β-glucan was carried out with the addition of Aspergillus aculeatus β-glucosidase produced by recombinant Aspergillus oryzae. Using EG-secreting C. glutamicum, 178 mg/l of glutamate was produced from 15 g of β-glucan. This is the first report of glutamate fermentation from β-glucan using endoglucanase-secreting C. glutamicum.     

The Effect of Exogenous β-<Emphasis Type="Italic">N-</Emphasis>Methylamino-<Emphasis Type="SmallCaps">l</Emphasis>-alanine on the Growth of <Emphasis Type="Italic">Synechocystis</Emphasis> PCC6803

β-N-Methylamino-l-alanine (BMAA), a non-proteinogenic amino acid, has been detected in a range of cyanobacteria, including terrestrial, aquatic, free living and endosymbiotic species. The widespread occurrence of cyanobacteria in the environment raises concerns regarding the ecological and toxicological impact of BMAA, and consequently, studies have focussed extensively on the toxicity and environmental impact of BMAA, while no research has addressed the ecophysiological or metabolic role of the compound in cyanobacteria. In this study, both the uptake of exogenous BMAA by and the effect of exogenous BMAA on the growth of Synechocystis PCC6803 were investigated. BMAA was rapidly taken up by the non-diazotrophic cyanobacterium Synechocystis PCC6803 in a concentration dependent manner. The presence of exogenous BMAA resulted in a substantial and concentration-dependent decrease in cell growth and the substantial loss of photosynthetic pigmentation. Similar effects were seen in the presence of the non-proteinogenic amino acid, 2,4-diaminobutyric acid but to a lesser degree than that of BMAA. The effects were reversed when light was decreased from 16 to 10 μmol m⁻² s⁻¹. Control cultures grown in the presence of l-arginine, l-asparagine, l-glutamate and glycine showed normal or slightly increased growth with no change in pigmentation. The decrease in growth rate coupled to bleaching indicates that BMAA may induce chlorosis in the presence of adequate photosynthetic radiation suggesting a connection between BMAA and the induction of conditions, such as nitrogen or sulphur depletion, that result in growth arrest and the induction of chlorosis.     

<Emphasis Type="Italic">Wax</Emphasis><Emphasis Type="Italic">crystal</Emphasis>-<Emphasis Type="Italic">sparse leaf 3</Emphasis> encoding a β-ketoacyl-CoA reductase is involved in cuticular wax biosynthesis in rice

Key message

WSL3 encodes β-ketoacyl-CoA reductase (KCR) in rice, in a similar way to YBR159w in yeast, and is essential for VLCFA biosynthesis and leaf wax accumulation.

Abstract

Cuticular waxes on plant surfaces limit non-stomatal water loss, protect plants against deposits of dust and impose a physical barrier to pathogen infection. We identified a wax-deficient mutant of rice, wax crystal-sparse leaf 3 (wsl3), which exhibits a pleiotropic phenotype that includes reduced epicuticular wax crystals on the leaf surface and altered wax composition. Map-based cloning demonstrated that defects in the mutant were caused by two adjacent single-nucleotide changes in a gene encoding β-ketoacyl-CoA reductase (KCR) that catalyzes the second step of the fatty acid elongation reaction. The identity of WSL3 was further confirmed by genetic complementation. Transient assays of fluorescent protein-tagged WSL3 in tobacco protoplasts showed that WSL3 localizes to the endoplasmic reticulum, the compartment of fatty acid elongation in cells. Quantitative PCR and histochemical staining indicated that WSL3 is universally expressed in tissues. RNA interference of WSL3 caused a phenotype that mimicked the wsl3 mutant. Very long-chain fatty acids (VLCFAs) 20:0 and 22:0, or 20:1Δ¹¹ and 22:1Δ¹³, were detected when WSL3 and Arabidopsis fatty acid elongation 1 (FAE1) were co-expressed in a yeast ybr159wΔ mutant strain. Our results indicated that WSL3 affects rice cuticular wax production by participating in VLCFA elongation.

     

Rapid induction of <Emphasis Type="Italic">Agrobacterium</Emphasis> <Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transgenic roots directly from adventitious roots in <Emphasis Type="Italic">Panax</Emphasis> <Emphasis Type="Italic">ginseng</Emphasis>

Root segments from seedlings of Panax ginseng produced adventitious roots directly when cultured on 1/2 MS solid medium lacking NH₄NO₃ and containing 3.0 mg l⁻¹ IBA. Using this adventitious root formation, we developed rapid and efficient transgenic root formation directly from adventitious root segments in P. ginseng. Root segments were co-cultivated with Agrobacterium tumefaciens (GV3101) caring β-glucuronidase (GUS) gene. Putative transgenic adventitious roots were formed directly from root segments on medium with 400 mg l⁻¹ cefotaxime and 50 mg l⁻¹ kanamycin. Kanamycin resistant adventitious roots were selected and proliferated as individual lines by subculturing on medium with 300 mg l⁻¹ cefotaxime and 50 mg l⁻¹ kanamycin at two weeks subculture interval. Frequency of transient and stable expression of GUS gene was enhanced by acetosyringon (50 mg l⁻¹) treatment. Integration of transgene into the plants was confirmed by the X-gluc reaction, PCR and Southern analysis. Production of transgenic plants was achieved via somatic embryogenesis from the embryogenic callus derived from independent lines of adventitious roots. The protocol for rapid induction of transgenic adventitious roots directly from adventitious roots can be applied for a new Agrobacterium tumefaciens-mediated genetic transformation protocol in P. ginseng.