Abstract:The 21-24 nucleotides small RNA that generated from double strands RNA can trigger two types of epigenetic gene silencing in plants. One is Post-Transcriptional Gene Silencing (PTGS), characterized by cleavage of homologous mRNA in cytoplasm. Transcriptional Gene Silencing (TGS) is another one, in which transcription inhibition is obtained through small RNA-directed DNA methylation of homologous promoter region. Here we summarized the relationship and differences between PTGS and TGS, the current achievement in the study of RNA silencing spreading, as well as the discrepancy of exogenous and endogenous gene silencing, and discussed the underlying reasons in the end.

Abstract:Two component system is a signal transduction system. It typically consists of a sensor histitine kinase and a cognate response regulator (RR) component. The activity of RR is regulated by a phosphorylation dependent mechanism. In recent years, the existence of atypical response regulators (ARRs), which rely on a phosphorylation independent mechanism to regulate their activity, have been recognized. ARRs are involved in the regulation of bacterial growth and development, antibiotic biosynthesis, iron transport, among others. Here we review the recent advances in the understanding of the structure and function of atypical response regulators, by using JadR1, a regulator in jadomycin biosynthesis in Streptomyces, as an example to elucidate the novel mechanism used by ARR to fine-tune its activity.

Abstract:Single-cell prokaryotes represent a simple and primitive cellular life form. The identification of the essential genes of bacteria and the minimal genome for the free-living cellular life could provide insights into the origin, evolution, and essence of life forms. The principles, methodology, and recent progresses in the identification of essential genes and minimal genome and the creation of synthetic cells are reviewed and particularly the strategies for creating the minimal genome and the potential applications are introduced.

Abstract:Influenza, caused by influenza virus, is a serious respiratory illness which poses a global public health threat. Vaccination is the primary strategy for the prevention and control of influenza. Although both inactivated vaccines and the live attenuated vaccines are effective in preventing influenza, the current vaccines have poor efficacy in the elderly and fail to provide protection against heterosubtype viruses. Development of a safer and more effective influenza vaccine that provides broad cross protection, overcoming the intrinsic limitation of the current vaccines, has been a scientific challenge. During the past decades, structural biology, reverse genetic and other virological technologies developed quickly and sped the progress of influenza vaccinology. Some new strategies for developing influenza vaccine have been generated, produced encouraging results, which showed great prospect as next-generation of influenza vaccines.

Abstract:Acetylcholinesterase (AChE) plays a key role in the pesticide determination. However, the extraction of AChE from natural materials has the disadvantages of low yield, complex purification and poor stability. Therefore, the preparation of recombinant AChE with high performance becomes the hot topic of researchers in recent years. In this article we summarize the progress in the expression of recombinant AChE and the improvement of its analytical characteristic. Finally, we point out that the directed evolution strategy combined with surface display technology is the future trend on improving recombinant AChE activity.

Abstract:Gene expression is regulated by different transcriptional regulators. The transcriptional regulator isocitrate lyase regulator (IclR) of Escherichia coli represses the expression of the aceBAK operon that codes for the glyoxylate pathway enzymes. In this study, physiological and metabolic responses of the deletion of the iclR gene in E. coli BW25113 were investigated based on the quantification and analysis of intracellular metabolic fluxes. The knockout of the iclR gene resulted in a decrease in the growth rate, glucose uptake rate and the acetate secretion rate, but a slight increase in biomass yield. The latter could be attributed to the lowered metabolic fluxes through several CO2 generating pathways, including the redirection of 33% of isocitrate directly to succinate and malate without CO2 production as well as the reduced flux through the pentose phosphate pathway. Furthermore, although the glyoxylate shunt was activated in the iclR mutant, the flux through phosphoenolpyruvate (PEP) carboxykinase kept almost unchanged, implying an inactive PEP-glyoxylate cycle and no extra loss of carbon atoms in the mutant strain. Both the reduced glucose uptake rate and the active glyoxylate shunt were responsible for the minor decrease in acetate secretion in the iclR knockout strain compared to that in the wild-type E. coli strain.

Abstract:Corynebacterium glutamicum is one of the most important traditional industrial microorganisms and receiving more and more attention towards a novel cellular factory due to the recently rapid development in genomics and genetic operation toolboxes for Corynebacterium. However, compared to other model organisms such as Escherichia coli, there were few studies on its metabolic regulation, especially a genome-scale integrated cellular network model currently missing for Corynebacterium, which hindered the systematic study of Corynebacterium glutamicum and large-scale rational design and optimization for strains. Here, by gathering relevant information from a number of public databases, we successfully constructed an integrated cellular network, which was composed of 1 384 reactions, 1 276 metabolites, 88 transcriptional factors and 999 pairs of transcriptional regulatory relationships. The transcriptional regulatory sub-network could be arranged into five layers and the metabolic sub-network presented a clear bow-tie structure. We proposed a new method to extract complex metabolic and regulatory sub-network for product-orientated study taking lysine biosynthesis as an example. The metabolic and regulatory sub-network extracted by our method was more close to the real functional network than the simplex biochemical pathways. The results would be greatly helpful for understanding the high-yielding biomechanism for amino acids and the re-design of the industrial strains.

Abstract:L-Arabinose isomerase (L-AI) is an intracellular enzyme that catalyzes the reversible isomerization of D-galactose and D-tagatose. Given the widespread use of D-tagatose in the food industry, food-grade microorganisms and the derivation of L-AI for the production of D-tagatose is gaining increased attention. In the current study, food-grade strains from different foods that can convert D-galactose to D-tagatose were screened. According to physiological, biochemical, and 16S rDNA gene analyses, the selected strain was found to share 99% identity with Pediococcus pentosaceus, and was named as Pediococcus pentosaceus PC-5. The araA gene encoding L-AI from Pediococcus pentosaceus PC-5 was cloned and overexpressed in E .coli BL21. The yield of D-tagatose using D-galactose as the substrate catalyzed by the crude enzyme in the presence of Mn2+ was found to be 33% at 40 °C.

Abstract:Genetic transformation was adopted to analyze the subcellular localization and the resistance to fungal pathogens of Arabidopsis lipid transfer protein AtDHyPRP1. The coding sequence of AtDHyPRP1 amplified by PCR from Ws ecotype was used to construct the plant binary expression vector pRI101-AN-AtDHyPRP1 and the fusion expression vector pCAMBIA1302- AtDHyPRP1-GFP. Transgenic tobacco and Arabidopsis plants were produced by leaf disc and floral dip protocols, respectively. AtDHyPRP1 could improve the resistance of tobacco to Botrytis cinerea remarkably and the infection sites on transgenic tobacco leaves accumulated large amounts of H2O2. Observation under laser scanning confocal microscope showed that AtDHyPRP1 was localized to cell surface. It suggested that AtDHyPRP1 might play special function after secretion to outside of the cell and was involved in plant defense system against pathogens.

Abstract:We developed a detailed electroporation method to deliver efficiently siRNA into mouse preimplantation embryos. By introducing Cy3 labeled negative control small interfering RNA (siRNA) into mouse preimplantation embryos, we optimized conditions for the electroporation, including the voltage, pulse duration, pulse number, electroporation buffer and an important step to weaken the zona pellucida. Embryonic survival rate, transfection rate and blastocyst development rate were evaluated under the converted fluorescence microscope, by embryos counting and statistical analysis. The best transfection was achieved in opti-MEM under the conditions of 30 V, 1 ms, 3 pulses, and the duration of digestion in tyrode’s solution was 10 s. In conclusion, the proposed electroporation approach here is a simple and efficient tool to deliver siRNA for RNA interference (RNAi) into mouse preimplantation embryos.

Abstract:The transcriptional factor Oct-4 and Survivin are the key regulatory factors in cancer cell proliferation and mitosis. A dual cancer-specific shRNA adenovirus vector, Ad5-Dual-shRNA, targeting Oct-4 and Survivin genes was constructed by molecular cloning and recombination. After cells were infected with virus, hepatocellular carcinoma cell line EHBH-H1 was used for detecting the expression of Oct-4 and Survivin proteins by Western blotting. The viral cytotoxic effect on cancer cells was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction assay in vitro, and the inhibition effect on tumor xenografts was observed in nude mice. The results showed that the expression of Oct-4 and Survivin in cancer cell line EHBH-H1 could be silenced markedly by Ad5-Dual-shRNA. In MTT and animal experiments, Ad5-Dual-shRNA also represented much stronger anti-tumor effect on tumor growth than Ad5-Surv-shRNA and Ad5-Oct4-shRNA. From this research we can draw a conclusion that the cancer-specific adenovirus vector expressing dual-shRNA targeting Oct-4 and Survivin genes may provide us a more effective, specific and convenient gene therapy method.

Abstract:To construct the recombinant adenovirus vector expressing specific siRNA for rat retinoic acid receptor-β (RARβ) gene, and to detect its effect on RARβ expression and neuronal differentiation of all-trans retinoic acid (ATRA) treated mesenchymal stem cells (MSCs). First, we designed four pairs of siRNA sequence for rat RARβ gene and annealed complementary oligonucleotides in vitro, then cloned double-stranded DNA in pSES-HUS vector containing U6/H1 double-promoter and recombinated with the backbone vector to construct pAd-siRARβ plasmid. We infected MSCs by using adenovirus Ad-siRARβ which was packaged in HEK293 cell line, then performed Real-time, Western blotting and immunoflourencence to detect the expression of RARβ. We used combination of ATRA and MNM to induce MSCs into neural-like cells, then performed Real-time PCR and immunoflourencence to detect neuronal specific markers of induced neural cells. By using PCR, endonuclease cutting and gene sequencing, we confirmed that the target genes were correctly cloned in adenovirus vector. We could observe more than 60% RFP-positive MSCs at 24 h after adenovirus infection. The expression of RARβ was significantly increased to 16.5±2.34 fold in ATRA treated MSCs (P<0.05) and located in nucleus. Three of four pairs siRNA could effectively inhibit the expression of RARβ with inhibition efficacy of (66.26±9.12)%, (48.70±5.78)%, (64.09±0.53)% (P<0.05), especially siRNA-pool group with inhibition efficacy of (78.09±4.24)% (P<0.01). Combination of ATRA and MNM induced MSCs into neural-like cells which expressed neuronal specific markers, Nestin, NSE, MAP-2, and Tau. Immunoflourencence result showed that about 50~88 present of cells were positive for Nestin, NSE, Tju1, however, adenovirus medicated expression of siRARβ could effectively inhibit the expression level of neural specific proteins and the ratio of positive stained cells (P<0.05). Therefore, we successfully constructed the recombinant adenovirus vector containing siRNA for rat RARβ gene, adenovirus could effectively infect MSCs and inhibit the expression of induced RARβ in ATRA treated MSCs, then inhibit neuronal differentiation of MSCs.