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Selectable Marker Gene (selectable + marker_gene)
Selected AbstractsExcision of selectable marker genes from transgenic crops as a concern for environmental biosafetyJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2007Satheesh Natarajan Abstract The main task in the development of transgenic plants is the capability to distinguish between plant cells with an integrated transgene and the bulk of non-transformed cells. Selectable marker genes are required to achieve this goal within the transgene, and to select for their expression. These selectable markers are mostly based on genes conferring antibiotic or herbicide resistance. The presence of the marker gene will lead to unpredictable environmental hazards, so on the basis of economic incentives and safety concerns, several methods, such as site-specific recombination, homologous recombination and co-transformation, have been developed to eliminate these genes from the genome after successful transformation has been achieved. Gene transfer without the incorporation of an antibiotic-resistance marker or herbicide-resistance marker in the host genome should convince the public with regard to the field release of transgenic organisms. Moreover, it would obviate the need for different selectable markers in subsequent rounds of gene transfer into the same host. Copyright © 2007 Society of Chemical Industry [source] Site-independently integrated transgenes in the elite restorer rice line Minghui 63 allow removal of a selectable marker from the gene of interest by self-segregationPLANT BIOTECHNOLOGY JOURNAL, Issue 3 2003Jumin Tu Summary In this study, we have demonstrated that two independent loci are involved in the integration of the insecticidal protein gene cryIAb/cryIAc and selectable marker gene hph in the recipient genome of the elite Chinese CMS restorer line Minghui 63. We have also documented the structural organization of these transgenes in each locus by restriction enzyme digestion and Southern blot analysis. The independent locus integration of different transgenes allowed us to remove the selectable marker gene hph from the gene of interest simply by self-segregation. Not having the selectable marker gene will enhance the commercial value of our transgenic line TT51-1, which showed a consistently high level of resistance against repeated infestations of yellow stem borers and natural outbreaks of leaf-folders, without a reduction in yield potential. [source] Consistent transcriptional silencing of 35S-driven transgenes in gentianTHE PLANT JOURNAL, Issue 4 2005Kei-ichiro Mishiba Summary In this study, no transgenic gentian (Gentiana triflora × Gentiana scabra) plants produced via Agrobacterium -mediated transformation exhibited transgene (GtMADS, gentian-derived MADS-box genes or sGFP, green fluorescent protein) expression in their leaf tissues, despite the use of constitutive Cauliflower mosaic virus (CaMV) 35S promoter. Strikingly, no expression of the selectable marker gene (bar) used for bialaphos selection was observed. To investigate the possible cause of this drastic transgene silencing, methylation-specific sequences were analysed by bisulfite genomic sequencing using tobacco transformants as a control. Highly methylated cytosine residues of CpG and CpWpG (W contains A or T) sites were distinctively detected in the promoter and 5, coding regions of the transgenes 35S- bar and 35S- GtMADS in all gentian lines analysed. These lines also exhibited various degrees of cytosine methylation in asymmetrical sequences. The methylation frequencies in the other transgene, nopaline synthase (NOS) promoter-driven nptII, and the endogenous GtMADS gene coding region, were much lower and were variable compared with those in the 35S promoter regions. Transgene methylation was observed in the bialaphos-selected transgenic calluses expressing the transgenes, and methylation sequences were distributed preferentially around the as-1 element in the 35S promoter. Calluses derived from leaf tissues of silenced transgenic gentian also exhibited transgene suppression, but expression was recovered by treatment with the methylation inhibitor 5-aza-2,-deoxycytidine (aza-dC). These results indicated that cytosine methylation occurs exclusively in the 35S promoter regions of the expressed transgenes during selection of gentian transformants, causing transcriptional gene silencing. [source] The role of double-strand break-induced allelic homologous recombination in somatic plant cellsTHE PLANT JOURNAL, Issue 3 2002Brigitte Gisler Summary During meiosis, homologous recombination occurs between allelic sequences. To evaluate the biological significance of such a pathway in somatic cells, we used transgenic tobacco plants with a restriction site for the rare cutting endonuclease I- SceI within a negative selectable marker gene. These plants were crossed with two tobacco lines containing, in allelic position, either a deletion or an insertion within the marker gene that rendered both marker gene and restriction site inactive. After the double-strand break induction, we selected for repair events resulting in a loss of marker gene function. This loss was mostly due to deletions. We were also able to detect double strand break-induced allelic recombination in which the break was repaired by a faithful copying process from the homologue carrying the shortened transgene. The estimated frequency indicates that homologous recombination in somatic cells between allelic sites appears to occur at the same order of magnitude as between ectopic sites, and is thus far too infrequent to act as major repair pathway. As somatic changes can be transferred to the germ line, the prevalence of intrachromatid rearrangements over allelic recombination might be an indirect prerequisite for the enhanced genome plasticity postulated for plants. [source] Excision of selectable marker genes from transgenic crops as a concern for environmental biosafetyJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2007Satheesh Natarajan Abstract The main task in the development of transgenic plants is the capability to distinguish between plant cells with an integrated transgene and the bulk of non-transformed cells. Selectable marker genes are required to achieve this goal within the transgene, and to select for their expression. These selectable markers are mostly based on genes conferring antibiotic or herbicide resistance. The presence of the marker gene will lead to unpredictable environmental hazards, so on the basis of economic incentives and safety concerns, several methods, such as site-specific recombination, homologous recombination and co-transformation, have been developed to eliminate these genes from the genome after successful transformation has been achieved. Gene transfer without the incorporation of an antibiotic-resistance marker or herbicide-resistance marker in the host genome should convince the public with regard to the field release of transgenic organisms. Moreover, it would obviate the need for different selectable markers in subsequent rounds of gene transfer into the same host. Copyright © 2007 Society of Chemical Industry [source] Production of biopharmaceuticals and vaccines in plants via the chloroplast genomeBIOTECHNOLOGY JOURNAL, Issue 10 2006Henry Daniell Dr.Article first published online: 27 SEP 200 Abstract Transgenic plants offer many advantages, including low cost of production (by elimination of fermenters), storage and transportation; heat stability; and absence of human pathogens. When therapeutic proteins are orally delivered, plant cells protect antigens in the stomach through bioencapsulation and eliminate the need for expensive purification and sterile injections, in addition to development of both systemic and mucosal immunity. Chloroplast genetic engineering offers several advantages, including high levels of transgene expression, transgene containment via maternal inheritance and multi-gene expression in a single transformation event. Hyper-expression of vaccine antigens against cholera, tetanus, anthrax, plague or canine parvovirus (4,31% of total soluble protein, tsp) in transgenic chloroplasts (leaves) or non-green plastids (carrots, tomato), as well as the availability of antibiotic-free selectable markers or the ability to excise selectable marker genes, facilitate oral delivery. Hyper-expression of several therapeutic proteins, including human serum albumin (11.1% tsp), somatotropin (7% tsp), interferon-gamma (6% tsp), anti-microbial peptide (21.5% tsp), facilitates efficient and economic purification. Also, the presence of chaperones and enzymes in chloroplasts facilitate assembly of complex multi-subunit proteins and correct folding of human blood proteins with proper disulfide bonds. Functionality of chloroplast-derived vaccine antigens and therapeutic proteins has been demonstrated by several assays, including the macrophage lysis assay, GM1-ganglioside binding assay, protection of HeLa cells or human lung carcinoma cells against encephalomyocarditis virus, systemic immune response, protection against pathogen challenge, and growth or inhibition of cell cultures. Thus, transgenic chloroplasts are ideal bioreactors for production of functional human and animal therapeutic proteins in an environmentally friendly manner. [source] | ||||||||||