Comparison of several Nicotiana species as hosts for high-scale Agrobacterium-mediated transient expression

Agrobacterium-mediated transient expression may be regarded as a promising method for inexpensive large-scale production of recombinant proteins. We optimized the protocol of transient expression in Nicotiana benthamiana and compared six Australian species of Nicotiana as hosts for transient expression. The transient expression of GFP under 35S CaMV promoter was observed in all species tested, although the GFP content in leaves of N. benthamiana, N. exigua, and N. excelsior was significantly higher (3.8, 3.7, and 2.0% TSP, respectively). Usage of viral-based expression system resulted in considerable increase of GFP accumulation in N. excelsior and N. benthamiana (63.5 and 16.2% TSP, respectively). We displayed that N. excelsior has the best characteristics in regard to biomass yield as well as GFP accumulation level for both types of the expression cassettes tested.     

Production of human interferon ALPHA 2b in plants of Nicotiana excelsior by Agrobacterium-mediated transient expression

Human interferon α2b gene was transiently expressed in Nicotiana excelsior plants. Fusion with N. plumbaginifolia calreticulin signal peptide for improved apoplast targeting and carrying out the expression under optimized conditions resulted in maximal interferon activity of 3.2 × 10³ IU/g fresh weight (FW) with an average of 2.1 ± 0.8 × 10³ IU/g FW. It proves that N. excelsior is a suitable host for Agrobacterium-mediated transient expression of genes encoding physiologically active human proteins. The transient expression conditions optimized for GFP marker protein were confirmed to be preferable for hIFN α2b.     

Heterologous expression of a Rauvolfia cDNA encoding strictosidine glucosidase, a biosynthetic key to over 2000 monoterpenoid indole alkaloids.

Strictosidine glucosidase (SG) is an enzyme that catalyses the second step in the biosynthesis of various classes of monoterpenoid indole alkaloids. Based on the comparison of cDNA sequences of SG from Catharanthus roseus and raucaffricine glucosidase (RG) from Rauvolfia serpentina, primers for RT-PCR were designed and the cDNA encoding SG was cloned from R. serpentina cell suspension cultures. The active enzyme was expressed in Escherichia coli and purified to homogeneity. Analysis of its deduced amino-acid sequence assigned the SG from R. serpentina to family 1 of glycosyl hydrolases. In contrast to the SG from C. roseus, the enzyme from R. serpentina is predicted to lack an uncleavable N-terminal signal sequence, which is believed to direct proteins to the endoplasmic reticulum. The temperature and pH optimum, enzyme kinetic parameters and substrate specificity of the heterologously expressed SG were studied and compared to those of the C. roseus enzyme, revealing some differences between the two glucosidases. In vitro deglucosylation of strictosidine by R. serpentina SG proceeds by the same mechanism as has been shown for the C. roseus enzyme preparation. The reaction gives rise to the end product cathenamine and involves 4,21-dehydrocorynantheine aldehyde as an intermediate. The enzymatic hydrolysis of dolichantoside (Nbeta-methylstrictosidine) leads to several products. One of them was identified as a new compound, 3-isocorreantine A. From the data it can be concluded that the divergence of the biosynthetic pathways leading to different classes of indole alkaloids formed in R. serpentina and C. roseus cell suspension cultures occurs at a later stage than strictosidine deglucosylation.     

FoxO1在胰岛β细胞代谢灵活性受损及失代偿进程中的作用

葡萄糖及脂肪酸是胰岛β细胞的关键代谢底物,葡萄糖刺激胰岛β细胞分泌胰岛素是维持机体血糖稳态平衡的关键。胰岛素抵抗发生时,β细胞对能量代谢底物的选择失调,加速胰岛β细胞由代偿到胰岛β细胞失代偿的进程,是肥胖胰岛素抵抗最终发展为2型糖尿病的始动因素。核转录因子FoxO1属于Fox家族成员,在胰腺内广泛表达,在β细胞的代谢,发育,增殖过程中发挥着重要的调节作用。鉴于FoxO1在维持胰岛β细胞功能中的关键作用,现着重对FoxO1在胰岛β细胞代谢灵活性受损及失代偿过程发生中的作用调节进行阐述。为其作为调控胰岛β细胞功能的关键靶点提供参考。     

Purification of recombinant GFP produced by Agrobacterum-mediated transient expression in Nicotiana excelsior

Green fluorescent protein (GFP) is commonly used as a reporter protein in a wide range of biological experiments. The efficient protocol of Agrobacterium-mediated transient expression in Nicotiana excelsior was applied for quick preparative production of recombinant GFP. The protein purification scheme has been developed and included ammonium sulfate precipitation and Q-sepharose anion-exchange chromatography. It results in obtaining of a fraction with about 85% GFP homogeneity and the protein yield of about 75%.     

Screening of plant cell culture collection for efficient host species for Agrobacterium-mediated transient expression

Agrobacterium-mediated transient expression is an approach for short-time expression of heterologous genes in plant systems. During the last decade transient expression was regarded as a potent protocol for high scale production of foreign proteins in plants including pharmaceutically valuable proteins. In vitro grown plant cell cultures represent a suitable system for accumulation of heterologous proteins under controlled conditions. Since host characteristics may strongly influence transient expression efficiency, we performed screening of undifferentiated cell cultures for transient expression ability using GUS as a reporter. Analysis of 248 plant species belonging to 49 families from the National Germplasm Bank of the World Flora of the Institute of Cell Biology and Genetic Engineering (Kyiv, Ukraine) allowed for selection of about 50 plant species exhibiting detectable β-glucuronidase activity.     

Recent advances in plant biotechnology and genetic engineering for production of secondary metabolites

For a long time people are using plants not only as crop cultures but also for obtaining of various chemicals. Currently plants remain one of the most important and essential sources of biologically active compounds in spite of progress in chemical or microbial synthesis. In our review we compare potentials and perspectives of modern genetic engineering approaches for pharmaceutical biotechnology and give examples of actual biotechnological systems used for production of several promising natural compounds: artemisinin, paclitaxel and scopolamine.     

Transfer of transformed <Emphasis Type="Italic">Lesquerella fendleri</Emphasis> (Gray) Wats. chloroplasts into <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis> (L.) O.E. Schulz by protoplast fusion

Asymmetric intergeneric hybrid plants were obtained through protoplast fusion between Orychophragmus violaceus (L.) O.E. Schulz and Lesquerella fendleri (Gray) Wats. The latter carried chloroplasts transformed with the fused aadA16gfp gene construct, conferring streptomycin–spectinomycin resistance and UV-induced green fluorescence. The somatic hybrids were selected using the properties of spectinomycin-induced plastid defects in “albino” O. violaceus plants (chloroplast recipient) combined with the γ-irradiation-induced inactivation of nuclei in plastid donor L. fendleri. The morphology and esterase isozyme pattern of the hybrid plant as well as the results of the PCR analysis of internal transcribed spacer of nuclear ribosomal DNA proved that the regenerated hybrids carried O. violaceus nuclei, while PCR amplification of the atpB– rbcL spacer and aadA16gfp gene fragments confirmed the presence of the transformed L. fendleri chloroplasts in these plants. Expression of the fused aadA16gfp gene construct was confirmed by sodium dodecylsulfate–polyacrylamide gel electrophoresis analysis and the resistance of the obtained plants to both streptomycin and spectinomycin.     

Establishment of transgenic lettuce plants producing potentially antihypertensive ShRNA

Development of RNAi-based therapeutics is a fast growing field of the pharmaceutical industry. Using plants for production of pharmaceutically valuable siRNAs may have significant advantages of costeffectiveness, scalability, and low risk of contamination with human pathogens. If edible plant species are genetically engineered to synthesize siRNAs, the costly stage of target product purification may be omitted. We describe the establishment of transgenic lettuce plants producing shRNA targeting delta isoform of protein kinase C (PKC-delta), an effective target for RNAi-based treatment of arterial hypertension. Transgenic lettuce plants were obtained by Agrobacterium-mediated transformation with genetic constructs harboring antiPKC and scrambled (control) shRNA genes. The presence of transgenes was proven by PCR analysis, and the accumulation of antiPKC shRNA was estimated using the RT-qPCR technique. Six transgenic lettuce lines showed varying levels of antiPKC shRNA expression with the highest value reaching 14 ± 9% of highly abundant endogenous lettuce micro RNA (miR156a), or 12.7 fmol/g dry weight. Plants carrying either antiPKC or scrambled shRNA genes flowered normally but did not produce seeds. The described transgenic lettuce plants accumulating antiPKC siRNA are the subject for animal testing and can be considered as raw material for the development of novel antihypertensive drugs.