China
Africa
Explore chapters and articles related to this topic
Genetic Regulation of Principal Microorganisms (Yeast, Zymomonas mobilis, and Clostridium thermocellum) Producing Bioethanol/Biofuel
Published in Ayerim Y. Hernández Almanza, Nagamani Balagurusamy, Héctor Ruiz Leza, Cristóbal N. Aguilar, Bioethanol, 2023
Dania Sandoval-Nuñez, Teresa Romero-Gutiérrez, Melchor Arellano-Plaza, Anne Gschaedler, Lorena Amaya-Delgado
Transcription has three steps in bacteria: first, RNA polymerase binds to a promoter site on DNA to form a closed complex; then, RNA polymerase starts transcription by opening the DNA duplex to form a transcription bubble. In the second stage, termed elongation, the transcription bubble moves along DNA, and the RNA chain is extended by adding nucleotides in the 5’ to 3’ direction. Finally, transcription stops, and the DNA duplex reforms when RNA polymerase dissociates at a terminator site. In bacteria, each gene or operon is flanked by a promoter and a terminator. The promoter is a specific nucleotide sequence site where the RNA polymerase binds to DNA and starts making RNA (mRNA). The terminator is a similar instruction in the DNA where the RNA polymerase stops transcribing mRNA and dissociates from the DNA. This mechanism is the purest form of gene expression regulation in bacteria. Essential components of transcription are sigma factors (σ), which are subunits of all bacterial RNA polymerases. They are responsible for determining the specificity of promoter DNA binding and efficiently control transcription initiation. In conclusion, the first step in bacterial gene expression and the step most often controlled is transcription. Regulatory factors usually determine whether a specific gene is transcribed by RNA polymerase or not under specific environmental conditions.
Protein Secretion Systems in Microbial and Mammalian Cells
Published in Juan A. Asenjo, Separation Processes in Biotechnology, 2020
Gene transfer techniques, such as calcium phosphate precipitation and electroporation, permit the introduction of DNA into mamalian hosts. Three major types of vector have been developed, each allowing establishment of permanent cell lines producing desired proteins. The bovine papilloma virus (BPV) vector can be maintained stably as a multicopy extrachromosomal plasmid in the host (Lusky and Botchan, 1984). Retroviral vectors may be propagated in virus particles which can infect a wide range of host cell lines, and the DNA can integrate into the chromosomes (Cepko et al., 1984). The third type of vector also integrates into the chromosomes upon transfection, but it carrys a selectable marker (Wigler et al., 1977; Robins et al., 1981). The gene encoding the protein of interest is generally introduced on a separate similar vector by co-transfection. Selectable markers such as the thymidine kinase (TK) gene (Wigler et al., 1977) and the dihydrofolate reductase (DHFR) gene (Lee et al., 1981) have been used to complement TK- or DHFR-deficient hosts. In addition, dominant selectable markers such as the bacterial gpt (xanthineguanine phosphoribosyltransferase) gene (Mulligan and Berg, 1981) and the neo (neomycin phosphotransferase) gene (Southern and Berg, 1982) can be used for selection in a much wider range of cell lines. Both constitutive and regulated promoters have been used for the expression of desired genes.
Bacillus thuringiensis: Transgenic Crops
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Biological and Ecological Systems, 2020
Julie A. Peterson, John J. Obrycki, James D. Harwood
The use of gene promoters that are tissue- or time-specific to express toxins only in plant tissues when they are susceptible to feeding has been introduced.[131] This technique has been employed in the transgenic expression of snowdrop lectin, a plant-derived protein with insecticidal properties, in rice. To target phloem-feeding pests such as brown planthoppers, lectins are selectively expressed in the vascular tissue.[132,133] Such selective expression of Bt toxins in tissue and time to target susceptible pests and reduce exposure to non-target beneficial arthropods could potentially increase environmental safety, thereby reducing the pathways for Bt toxin movement through non-target food webs.
Synthesis of programmable biological central processing system
Published in Journal of the Chinese Institute of Engineers, 2021
Wei-Xian Li, Jiangfeng Cheng, Chun-Liang Lin, Chia-Feng Juang
The TF bound to upstream DNA initiates transcription of the RNA polymerase bound to the promoter region. The reaction processes of the biological logic gates are based on the TF bound to the DNA upstream sites. The synthesized protein is the result of the RNA polymerase binding to the DNA; it can be a TF for synthesizing biological gates (Lauria et al. 2004; Buchler, Gerland, and Hwa 2003). This can be implemented by choosing a gene for the first gate and encoding the protein that acts as a TF for the second gate.
Phytoremediation of petroleum-contaminated soil by Salicornia: from PSY activity to physiological and morphological communications
Published in Environmental Technology, 2019
Tayebe Abdollahzadeh, Ali Niazi, Ali Moghadam, Zohreh Heydarian, Reza Ghasemi-Fasaei, Elina Kaviani, Neda Pourdad
According to the presented results, the highest amount of carotenoids was observed in 0.2% petroleum-contaminated soil (Figure 6(g,h)) while it was in parallel with the expression increase of PSY (Figure 5). It means that both PSY expression and carotenoid content increased in 0.2% petroleum-contaminated soil. However, the induction of the PSY expression was significantly increased 1 h after 0.2% petroleum stress (Figure 5(a) and Table S5a). The expression level of PSY showed twice more increase than control at 10 h after stress (Figure 5(a)). Although the control at 10 h increased compared to the control at 1 h after 0.2% petroleum stress, as shown in Figure 5(a), the increase of PSY expression at 10 h after stress was more than in the control. This slight increase in control is related to the light-responsive cis-acting elements (Table 3). It means that PSY with these motifs is a light-responsive gene and is regulated with light. These motifs are short sequences of DNA within a gene promoter region that are able to bind specific transcription factors and regulate transcription of genes. A transcription activator protein binds to the responsive element and stimulates transcription under light conditions [46]. In addition, PSY showed a significant increase in expression in long-term stress in 0.2% petroleum contamination (Figure 5(b) and Table S5b). Overall the expression of PSY increased in both short-term and long-term stresses in 0.2% petroleum (Figure 5). Rapid induction of Oryza sativa PSY3 due to salt treatment can be considered as the cause of plant resistance in osmotic stress [23]. Moreover, expression analysis of OsPSY3 following ABA treatment showed a significant increase in the level of OsPSY3, which remained stable even 6 h after treatment [23]. Also, Haematococcus pluvialis Flotow exposed to nutrient stress showed a higher level of the PSY transcript, which reached a maximum level two days after stress [47]. In short-term stress, the PSY expression level in 2% petroleum significantly reduced compared with the control in the first few hours of stress and the gene expression level significantly dropped 10 h after stress compared with the control (Figure 5(a)). Furthermore, the PSY expression level dropped significantly in 2% petroleum under long-term stress (Figure 5(b)). Hence, a downward trend of PSY expression under short- and long-term stresses was indicated in 2% petroleum (Figure 5 and Table S5a and S5b).