Microbial transformation of ginsenosides Rb1, Rb3 and Rc by Fusarium sacchari

Aims: This study examined the transformation pathways of ginsenosides G‐Rb₁, G‐Rb₃, and G‐Rc by the fungus Fusarium sacchari. Methods and Results: Ginsenosides G‐Rb₁, G‐Rb₃ and G‐Rc were isolated from leaves of Radix notoginseng, and their structural identification was confirmed using NMR. Transformation of G‐Rb₁, G‐Rb₃ and G‐Rc by Fusarium sacchari was respectively experimented. Kinetic evolutions of G‐Rb₁, G‐Rb₃ and G‐Rc and their metabolites during the cell incubation were monitored by HPLC analysis. High‐performance liquid chromatography (HPLC) was used for monitoring the transformation kinetics of bioactive compounds during F. sacchari metabolism. Conclusions: Ginsenoside C‐K was transformed by F. sacchari from G‐Rb₁ via G‐Rd or via G‐F₂, or from G‐Rb₁ via firstly Rd and then G‐F₂, and C‐Mx was transformed by F. sacchari or directly from Rb₃, or from Rb₃ via Gy‐IX, while G‐Mc was transformed by F. sacchari directly from G‐Rc. Furthermore, C‐K could be also formed from G‐Rc via notoginsenoside Fe (N‐Fe). Significance and Impact of the Study: The results showed an important practical application in the preparation of ginsenoside C‐K. As our precious research indicated C‐K possessed much more antitumor activities than C‐Mx and G‐Mc, so according to the transformation pathways proposed by this work, the production of antitumor compound C‐K may be performed by biotransformation of G‐Rb₁ previously isolated from PNLS.     

Highly selective microbial transformation of major ginsenoside Rb(1) to gypenoside LXXV by Esteya vermicola CNU120806

Aims

This study examined the biotransformation pathway of ginsenoside Rb₁ by the fungus Esteya vermicola CNU 120806.

Methods and Results

Ginsenosides Rb₁ and Rd were extracted from the root of Panax ginseng. Liquid fermentation and purified enzyme hydrolysis were employed to investigate the biotransformation of ginsenoside Rb₁. The metabolites were identified and confirmed using NMR analysis as gypenoside XVII and gypenoside LXXV. A mole yield of 95·4% gypenoside LXXV was obtained by enzymatic conversion (pH 5·0, temperature 50°C). Ginsenoside Rd was used to verify the transformation pathway under the same reaction condition. The product Compound K (mole yield 49·6%) proved a consecutive hydrolyses occurred at the C‐3 position of ginsenoside Rb₁.

Conclusions

Strain CNU 120806 showed a high degree of specific β‐glucosidase activity to convert ginsenosides Rb₁ and Rd to gypenoside LXXV and Compound K, respectively. The maximal activity of the purified glucosidase for ginsenosides transformation occurred at 50°C and pH 5·0. Compared with its activity against pNPG (100%), the β‐glucosidase exhibited quite lower level of activity against other aryl‐glycosides. Enzymatic hydrolysate, gypenoside LXXV and Compound K were produced by consecutive hydrolyses of the terminal and inner glucopyranosyl moieties at the C‐3 carbon of ginsenoside Rb₁ and Rd, giving the pathway: ginsenoside Rb₁→ gypenoside XVII → gypenoside LXXV; ginsenoside Rd→F₂→Compound K, but did not hydrolyse the 20‐C, β‐(1‐6)‐glucoside of ginsenoside Rb₁ and Rd.

Significance and Impact of the Study

The results showed an important practical application on the preparation of gypenoside LXXV. Additionally, this study for the first time provided a high efficient preparation method for gypenoside LXXV without further conversion, which also gives rise to a potential commercial enzyme application.     

An endophytic bacterium isolated from Panax ginseng C.A. Meyer enhances growth,reduces morbidity,and stimulates ginsenoside biosynthesis

Ginseng (Panax ginseng C.A. Meyer) is known for its therapeutically useful ginsenosides that have anticancer and other pharmacological effects. However, its low levels in plants and the high costs of chemical synthesis make ginsenosides commercially non-viable; as such, strategies for increasing ginsenoside yield are of great interest. The present study reports the isolation of eight novel endophytic bacteria from ginseng leaves, the highest ginsenoside concentration of microbial transformed strain was identified as Paenibacillus polymyxa. Inoculation of ginseng plants with P. polymyxa by foliar application combined with irrigation enhanced plant growth parameters, reduced morbidity, and increased plant concentration of the ginsenosides (Rg₁, Re, Rf, Rb₁, Rg₂, Rb₂, Rb₃, and Rd) in field experiments. These results indicate that P. polymyxa isolated from ginseng is a beneficial endophytic bacterium with biocontrol properties that can enhance the yield and quality of this medicinal plant.     

A new ginsenosidase from Aspergillus strain hydrolyzing 20-O-multi-glycoside of PPD ginsenoside

A ginsenosidase specifically hydrolyzing multi-20-O-glycosides of protopanaxadiol type ginsenosides such as ginsenoside Rb₁, Rb₃, Rb₂ and Rc, named ginsenosidase type II, was isolated and purified from Aspergillus sp.g48p strain. The molecular weight of the enzyme was 60 kDa. Ginsenosidase type II was demonstrated to hydrolyze multi-20-O-glycoside of protopanaxadiol type ginsenoside Rb₁, Rb₃, Rb₂ and Rc; i.e. the ginsenosidase type II hydrolyzes 20-O-β-glucoside of the ginsenoside Rb₁, 20-O-β-xyloside of ginsenoside Rb₃, 20-O-α-arabinoside(p) of ginsenoside Rb₂ and α-arabinoside(f) of ginsenoside Rc to produce mainly ginsenoside Rd, and small amount of Rg₃. However, it did not hydrolyze 3-O-β-glucosides of ginsenoside Rb₁, Rb₃, Rb₂ and Rc which was different with the ginsenosidase type I previously reported, either did not hydrolyze the glycosides of protopanaxatriol type ginsenoside such as ginsenoside Re, Rf and Rg₁, showing significant difference from all previously described glycosidases.     

Ginsenoside Rd production from the major ginsenoside Rb<Subscript>1</Subscript> by <Emphasis Type="Italic">β</Emphasis>-glucosidase from <Emphasis Type="Italic">Thermus caldophilus</Emphasis>

Under optimum conditions (pH 5, 75°C, and 0.2 U purified enzyme ml⁻¹), 4 mg ginsenoside Rd was produced from 5 mg reagent-grade ginsenoside Rb₁ in 5 ml after 30 min by β-glucosidase from Thermus caldophilus GK24. Using a ginseng root extract containing 1 mg ginsenoside Rb₁ ml⁻¹ and 3.2 mg additional ginsenosides ml⁻¹, 1.23 mg ginsenoside Rd ml⁻¹ was produced after 18 h; the concentrations of ginsenosides Rb₁, Rb₂, and Rc used for ginsenoside Rd production were 0.77, 0.17, and 0.19 mg ml⁻¹, respectively.     

Comparison of ginsenoside composition in native roots and cultured callus cells of Panax quinquefolium L.

In order to compare the ginsenoside composition in native Panax quinquefolium and in suspension cultured cells derived from root callus, HPLC–ESI-MSⁿ analysis was performed. Under the present HPLC–ESI-MSⁿ conditions, ten ginsenosides from native root were acquired in the positive and negative ion modes, namely Rg₁, Re, Ro, malonyl-Rb₁, Rf, Rb₁, Rc, Rb₂, Rb₃ and Rd. Only four ginsenosides (Rg1, Re, Rf and Rb1) were identified from callus cells. Radical scavenging activity of P. quinquefolium callus cells with 250 mg l^?1 methanolic extract on 1,1-diphenyl-2-picrylhydrazyl (DPPH) was 55.72 %, while only 6.31 % DPPH inhibition was obtained in native root.     

Growth and biosynthetic characteristics of ginseng (Panax japonicus var. repens) deep-tank cell culture in bioreactors

The aim of the work was to study the growth characteristics of cultured cells of Panax japonicus var. repens, an endemic plant of the Primorski Krai of Russia, grown in laboratory bioreactors and to determine the content of basic ginsenosides under these conditions. An increase of the inoculum size of the culture produced higher biomass accumulation and economic coefficient but slightly reduced the specific growth rate. An increase in the auxin concentration in a medium by adding 2,4-D practically did not affect growth characteristics of the culture but significantly reduced the size of cell aggregates. In all treatments tested, all major ginsenosides (Rb₁, Rc, Rb₂, Rd, Rf, Rg₁, and Re) were found in the culture. The total ginsenoside content was 2–3% per biomass dry weight. Meantime, ginsenosides of the Rg-series with protopanaxatriol as aglycone prevailed (70% of the total ginsenoside content). The culture conditions considerably affected the ratio of individual ginsenosides. In 2,4-D-containing medium, the preferential synthesis of Re ginsenoside was observed while both Rg₁ and Re were synthesized in other treatments.     

Production of saponins from <Emphasis Type="Italic">Panax ginseng</Emphasis> suspension and adventitious root cultures

Biomass growth and ginsenoside production in cell suspension and adventitious roots of Panax ginseng C.A. Meyer cultures cultivated both in Erlenmayer flasks and a 3 dm³ bioreactor were studied. The maximum content of ginsenosides was found in the suspension culture cultivated in the bioreactor (4.34 % dry mass), however the saponin content was limited to two major ginsenosides, Rb₁ and Rg₁. The production of ginsenosides in adventitious roots was lower (1.45 or 1.72 % dry mass), nevertheless, the full range of ginsenosides was detected.This work was supported by 521/02/P064, COST 843.10, ME671 and Z4 055 905 projects.     

Bioconversion of ginsenosides Rb(1), Rb(2), Rc and Rd by novel β-glucosidase hydrolyzing outer 3-O glycoside from Sphingomonas sp. 2F2: cloning, expression, and enzyme characterization

A new β-glucosidase gene (bglSp) was cloned from the ginsenoside converting Sphingomonas sp. strain 2F2 isolated from the ginseng cultivating filed. The bglSp consisted of 1344 bp (447 amino acid residues) with a predicted molecular mass of 49,399 Da. A BLAST search using the bglSp sequence revealed significant homology to that of glycoside hydrolase superfamily 1. This enzyme was overexpressed in Escherichia coli BL21 (DE3) using a pET21-MBP (TEV) vector system. Overexpressed recombinant enzymes which could convert the ginsenosides Rb₁, Rb₂, Rc and Rd to the more pharmacological active rare ginsenosides gypenoside XVII, ginsenoside C-O, ginsenoside C-Mc₁ and ginsenoside F₂, respectively, were purified by two steps with Amylose-affinity and DEAE-Cellulose chromatography and characterized. The kinetic parameters for β-glucosidase showed the apparent K_m and V_max values of 2.9 ± 0.3 mM and 515.4 ± 38.3 μmol min⁻¹ mg of protein⁻¹ against p-nitrophenyl-β-d-glucopyranoside. The enzyme could hydrolyze the outer C3 glucose moieties of ginsenosides Rb₁, Rb₂, Rc and Rd into the rare ginsenosides Gyp XVII, C-O, C-Mc₁ and F₂ quickly at optimal conditions of pH 5.0 and 37 °C. A little ginsenoside F₂ production from ginsenosides Gyp XVII, C-O, and C-Mc₁ was observed for the lengthy enzyme reaction caused by the side ability of the enzyme.     

Improvement of ginsenoside production by <Emphasis Type="Italic">Panax ginseng</Emphasis> adventitious roots induced by γ-irradiation

In order to evaluate effects of γ-rays on adventitious root formation and ginsenoside production, embryogenic calli induced from cotyledon explants of Panax ginseng C.A. Meyer were treated with γ-rays of 0, 10, 30, 50, 70, and 100 Gy. The highest frequency of adventitious root formation of 75 % occurred at γ-irradiation of 30 Gy, which is considered adequate dosage for selecting mutant cell lines. Five mutated adventitious roots (MAR)3-lines out of the propagation of 142 adventitious root lines treated with 30 Gy were selected based a 100-fold increase in proliferation rate compared to control adventitious roots (CAR) and content of the seven major ginsenosides (Rb₁, Rb₂, R_c, R_d, R_e, R_f, and Rg₁) was determined. In the CAR and four of the MAR3-lines (except for MAR3-109), the Rb/Rg ratio was greater than 1.0, thereby indicating altered ginsenoside composition in these root lines. The HPLC analysis of the MAR3-13 and MAR3-26 lines confirmed different ginsenoside profiles, including the three unidentified ginsenoside candidates, Gm₁, Gm₂, and Gm₃. The ginsenosides of the MAR3-13 and MAR3-26 lines showed high hydroxyl and superoxide radical scavenging activities.     

Ginsenoside F1 production from ginsenoside Rg1 by a purified β-glucosidase from Fusarium moniliforme var. subglutinans

Fusarium moniliforme var. subglutinans was selected from among 100 strains of fungi for producing ginsenoside F₁ from ginsenoside Rg₁. The enzyme responsible was purified as a single 85 kDa band with a specific activity of 136 U mg⁻¹. It hydrolysed glucose-linked ginsenosides Rb₁, Rd and Rg₁ but not for other monosaccharide-linked ginsenosides, Rb₂, Rc, R₁, and Re. Under the optimum conditions of pH 6.0, 50°C, 30 U l⁻¹ of enzyme, and 5 mg Rg₁ ml⁻¹, 4 mg F₁ ml⁻¹ was produced after 4 h, with a molar yield of 100% and a productivity of 1 g l⁻¹ h⁻¹. This represents the highest productivity and conversion yield of F₁ yet reported.     

Co-transformation of <Emphasis Type="Italic">Panax</Emphasis> major ginsenosides Rb<Subscript>1</Subscript> and Rg<Subscript>1</Subscript> to minor ginsenosides C–K and F<Subscript>1</Subscript> by <Emphasis Type="Italic">Cladosporium cladosporioides</Emphasis>

Rb₁ and Rg₁ are the major ginsenosides in protopanaxadiol and protopanaxatriol. Their content in ginsenosides was 23.8 and 17.6%, respectively. A total of 22 isolates of β-glucosidase producing microorganisms were isolated from the soil of a ginseng field using Esculin-R2A agar. Among these isolates, the strain GH21 showed the strongest activities to convert ginsenoside Rb₁ and Rg₁ to minor ginsenosides compound-K and F₁, respectively. Ginsenosides Rb₁ and Rg₁ bioconversion rates were 74.2 and 89.3%, respectively. Meanwhile, the results demonstrated that the ginsenoside Rg₁ could change the biotransformation pathway of ginsenoside Rb₁ by inhibiting the formation of the intermediate metabolite gypenoside-XVII. GH21 was identified as a Cladosporium cladosporioides species based on the internal transcribed spacers (ITS) ITS1-5.8S-ITS2 rRNA gene sequences constructed phylogenetic trees.     

β-Glucosidase from Penicillium aculeatum hydrolyzes exo-, 3-O-, and 6-O-β-glucosides but not 20-O-β-glucoside and other glycosides of ginsenosides

A novel β-glucosidase from Penicillium aculeatum was purified as a single 110.5-kDa band on SDS–PAGE with a specific activity of 75.4 U?mg^?1 by salt precipitation and Hi-Trap Q HP and Resource Q ion exchange chromatographies. The purified enzyme was identified as a member of the glycoside hydrolase 3 family based on its amino acid sequence. The hydrolysis activity for p-nitrophenyl-β-d-glucopyranoside was optimal at pH 4.5 and 70 °C with a half-life of 55 h. The enzyme hydrolyzed exo-, 3-O-, and 6-O-β-glucosides but not 20-O-β-glucoside and other glycosides of ginsenosides. Because of the novel specificity, this enzyme had the transformation pathways for ginsenosides: Rb₁?→?Rd?→?F₂?→?compound K, Rb₂?→?compound O?→?compound Y, Rc?→?compound Mc₁?→?compound Mc, Rg₃?→?Rh₂?→?aglycone protopanaxadiol (APPD), Rg₁?→?F₁, and Rf?→?Rh₁?→?aglycone protopanaxatriol (APPT). Under the optimum conditions, the enzyme converted 0.5 mM Rb_2, Rc, Rd, Rg₃, Rg₁, and Rf to 0.49 mM compound Y, 0.49 mM compound Mc, 0.47 mM compound K, 0.23 mM APPD, 0.49 mM?F₁, and 0.44 mM APPT after 6 h, respectively.     

Effects of ginsenosides on carbachol-stimulated formation of inositol phosphates in rat cortical cell cultures

We examined the effect of ginseng total saponins (GTS) on phosphoinositide metabolism stimulated by activation of muscarinic receptor using rat cortical cultures. Carbachol stimulated formation of [³H]inositol phosphates ([³H]InsPs) by 3.3-fold over basal level in [³H]inositol-prelabeled cells. Pretreatment of GTS inhibited formation of [³H]InsPs evoked by carbachol by 70%–90%. Addition of GTS alone had no effect on the basal formation of [³H]InsPs. The inhibitory effect of the GTS on carbachol-stimulated formation of [³H]InsPs was dose- and time-dependent. IC₅₀ was 6.0 ± 2.8 g/ml. We also examined the effect of GTS on [³H]InsP₁, [³H]InsP₂, or [³H]InsP₃ formation evoked by carbachol. Although GTS had no effect on the basal [³H]InsP₁, [³H]InsP₂, or [³H]InsP₃ formation, pretreatment of GTS inhibited [³H]InsP₁, [³H]InsP₂, or [³H]InsP₃ formation evoked by carbachol, respectively. Addition of individual ginsenosides such as ginsenoside Rb₁, Rc, Rd, Re, or Rg₂ had no effect on the basal formation of [³H]InsPs, whereas pretreatment of ginsenoside Rb₂, Rc, Rd, Re, Rf, Rg₁ or Rg₂ inhibited formation of [³H]InsPs evoked by carbachol by 79%–89%. The results suggest that the inhibitory effect of GTS and its individual ginsenosides on carbachol-stimulated formation of [³H]InsPs in cortical neurons could be one pharmacological action of Panax ginseng.     

二甲酸钾对白羽肉鸡生长性能和肠道菌群结构的影响

为评估二甲酸钾对畜禽肠道菌群的影响及其作为一种抗饲料添加剂的应用潜力,采用3日龄健康白羽肉鸡作为饲喂对象,在基础饲粮基础上添加质量浓度为0.1%、0.3%、0.5%、0.7%的二甲酸钾和含量为50 mg/mL的金霉素分别进行比较饲喂管理。记录28 d试验周期内白羽肉鸡的料重比变化,采集28 d时白羽肉鸡盲肠肠道内溶物,利用第三代测序技术对肠道菌群进行16S rDNA全长序列高通量测序。结果显示,饲喂0.3%的二甲酸钾能够显著降低料重比,对白羽肉鸡的生长性能具有明显的促进作用。饲喂0.3%的二甲酸钾对白羽肉鸡的肠道菌群结构造成了一定的影响,有效地提高了肠道菌群的物种多样性。优势菌群中,饲喂0.3%二甲酸钾与空白组相比,在门水平上,拟杆菌门相对丰度显著上升,厚壁菌门、变形菌门和Epsilonbacteraeota的相对丰度下降,产生了更有利于生长发育的微生物群落。同时,在属水平上,拟杆菌属相对丰度显著上升, Barnesiella和螺杆菌属的相对丰度下降,改善了肠道中微生物菌群的微生态健康。研究结果丰富了二甲酸钾和金霉素对白羽肉鸡生长性能和肠道菌群影响的认识,也为更全面了解二甲酸钾应用于替代抗生素对畜禽的影响提供了有价值的微生物学信息。     

Characterization of recombinant β-glucosidase from Arthrobacter chlorophenolicus and biotransformation of ginsenosides Rb1, Rb2, Rc,and Rd

The focus of this study was the cloning, expression, and characterization of recombinant ginsenoside hydrolyzing β-glucosidase from Arthrobacter chlorophenolicus with an ultimate objective to more efficiently bio-transform ginsenosides. The gene bglAch, consisting of 1,260 bp (419 amino acid residues) was cloned and the recombinant enzyme, overexpressed in Escherichia coli BL21 (DE3), was characterized. The GST-fused BglAch was purified using GST·Bind agarose resin and characterized. Under optimal conditions (pH 6.0 and 37°C) BglAch hydrolyzed the outer glucose and arabinopyranose moieties of ginsenosides Rb1 and Rb2 at the C20 position of the aglycone into ginsenoside Rd. This was followed by hydrolysis into F₂ of the outer glucose moiety of ginsenoside Rd at the C3 position of the aglycone. Additionally, BglAch more slowly transformed Rc to F₂ via C-Mc₁ (compared to hydrolysis of Rb₁ or Rb₂). These results indicate that the recombinant BglAch could be useful for the production of ginsenoside F₂ for use in the pharmaceutical and cosmetic industries.     

High Density Cultivation of Panax notoginseng Cell Cultures with Methyl Jasmonate Elicitation in a Centrifugal Impeller Bioreactor

True ginseng roots contain “active compounds” called ginsenosides. The enhanced production of useful bioactive ginsenosides by high‐density cell cultures of Panax notoginseng in a self‐developed centrifugal impeller bioreactor (CIB) was achieved by adding methyl jasmonic acid (MJA) during cultivation. The production of the major, individual ginsenosides Rg₁, Re and Rb₁ was significantly enhanced in both 3‐L and 30‐L CIBs. The production titer of Rg₁, Re and Rb₁ ginsenosides in the 30‐L CIB was improved from 42 ± 8, 42 ± 9 and 41 ± 6 mg/L without MJA elicitation, to 104 ± 6, 71 ± 5 and 95 ± 6 mg/L with MJA elicitation, respectively. The ratio of Rb/Rg was slightly improved by MJA treatment in a 3‐L CIB but no apparent difference was observed in a 30‐L CIB. This work is useful for the understanding of the effects of large‐scale production on the individual ginseng saponins produced by plant cell cultures     

Autotoxic Ginsenosides in the Rhizosphere Contribute to the Replant Failure of Panax notoginseng

MethodsThe autotoxicities were measured using seedling emergence bioassays and root cell vigor staining. The ginsenosides in the roots, soils, and root exudates were identified with HPLC-MS.ResultsThe seedling emergence and survival rate decreased significantly with the continuous number of planting years from one to three years. The root exudates, root extracts, and extracts from consecutively cultivated soils also showed significant autotoxicity against seedling emergence and growth. Ginsenosides, including R₁, Rg₁, Re, Rb₁, Rb₃, Rg₂, and Rd, were identified in the roots and consecutively cultivated soil. The ginsenosides, Rg₁, Re, Rg₂, and Rd, were identified in the root exudates. Furthermore, the ginsenosides, R₁, Rg₁, Re, Rg₂, and Rd, caused autotoxicity against seedling emergence and growth and root cell vigor at a concentration of 1.0 µg/mL.ConclusionOur results demonstrated that autotoxicity results in replant failure of Sanqi ginseng. While Sanqi ginseng consecutively cultivated, some ginsenosides can accumulate in rhizosphere soils through root exudates or root decomposition, which impedes seedling emergence and growth.     

西方蜜蜂工蜂肠道菌群定殖起始点和定殖稳态点的结构比较分析

【目的】目前,针对昆虫肠道细菌定殖规律的研究还未见报道。探索西方蜜蜂(Apis mellifera)肠道菌群定殖过程两个重要时间节点(起始0日龄和稳态7日龄)间肠道细菌群落(菌群)结构组成的差异,加深对蜜蜂及昆虫肠道菌群定殖规律的认识。【方法】分别采集两个化蛹后工蜂发育阶段的个体各5只,分别解剖并提取其肠道菌群DNA。使用Illumina技术对肠道菌群16S rD NA高变区进行高通量测序。通过生物信息学的分析方法对肠道菌群进行多样性分析,并对两个时间点相对丰度最高的肠道菌群进行统计分析,比较肠道菌群相对丰度和组成的差异。【结果】共获得515156条高质量序列,长度为227904953bp,平均长度为442bp。基于OTUs的分类表明,工蜂肠道细菌分别隶属于34个门82个纲221个目405个科799个属。此外,工蜂肠道菌群定殖起点和终点间的Alpha多样性指数存在显著差异(ACE,P=0.0014;Chao,P=0.0013;Shannon,P=0.0003;Simpson,P=0.0028,Student’s t检验)。此外,相较0日龄工蜂,7日龄工蜂肠道中的乳酸杆菌Lactobacillus、Gilliamella、双歧杆菌Bifidobacterium、Snodgrassella4个属的相对丰度显著增加;相反,不动杆菌Acinetobacter、大肠杆菌志贺氏菌Escherichia-Shigella、鞘脂单胞菌Sphingomonas、类杆菌Bacteroides、涅斯捷连科氏菌Nesterenkonia、栖热菌Thermus6个属的细菌相对丰度显著降低(P0.05)。【结论】出房(0日龄)成年工蜂的肠道菌群多样性显著高于菌群定殖完成(7日龄)工蜂的肠道菌群多样性,且成年工蜂肠道菌群定殖完成前后部分类群的相对丰度显著改变。本研究的结果不仅可增加我们对蜜蜂肠道菌群定殖规律的认识,也能够为研究其他昆虫肠道菌群的定殖规律提供重要的参考信息。     

Ginsenoside Rb1 in asymmetric somatic hybrid calli of Daucus carota with Panax quinquefolius

American ginseng (Panax quinquefolius L.) is one of the most valuable herbs in the world. Its major active components are ginsenosides. In order to produce ginsenoside heterogeneously, somatic hybridization, a novel approach for genetic introgression, was employed in this study. Protoplasts derived from respective calli of carrot (Daucus carota var. sativus Hoffm.) and American ginseng (P. quinquefolius L.) were used as the fusion partners. Hybrid calli derived from single cell lines containing chromatin of American ginseng were confirmed by the analyses of isozyme, Random amplified polymorphic DNA (RAPD) and genomic in situ hybridization (GISH). High performance liquid chromatography (HPLC) results showed that the ginseng monomer Rb₁ was synthesized in seven of the hybrid calli identified as well as in the parent American ginseng calli but not in the parent carrot calli. Results indicated that hybrid introgression lines could produce ginsenoside Rb₁ and the ginsenoside Rb₁ biosynthesis pathway has been introgressed into carrot cells via somatic hybridization. From the point of biosafety view concerning the consumer acceptance, the potential predominance to produce ginsenosides with somatic hybridization other than with genetic transformation is discussed. Lu Han and Chuanen Zhou contributed equally to this work.