scholarly journals ptxD/Phi as alternative selectable marker system for genetic transformation for bio-safety concerns: a review

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11809
Author(s):  
Richard Dormatey ◽  
Chao Sun ◽  
Kazim Ali ◽  
Sajid Fiaz ◽  
Derong Xu ◽  
...  
Keyword(s):  
Transgenic Plants ◽  
Genetic Transformation ◽  
Herbicide Resistance ◽  
Selectable Marker ◽  
Selection Marker ◽  
Marker Genes ◽  
Selection System ◽  
Efficient System ◽  
Marker System ◽  
Selectable Marker Genes

Antibiotic and herbicide resistance genes are the most common marker genes for plant transformation to improve crop yield and food quality. However, there is public concern about the use of resistance marker genes in food crops due to the risk of potential gene flow from transgenic plants to compatible weedy relatives, leading to the possible development of “superweeds” and antibiotic resistance. Several selectable marker genes such as aph, nptII, aaC3, aadA, pat, bar, epsp and gat, which have been synthesized to generate transgenic plants by genetic transformation, have shown some limitations. These marker genes, which confer antibiotic or herbicide resistance and are introduced into crops along with economically valuable genes, have three main problems: selective agents have negative effects on plant cell proliferation and differentiation, uncertainty about the environmental effects of many selectable marker genes, and difficulty in performing recurrent transformations with the same selectable marker to pyramid desired genes. Recently, a simple, novel, and affordable method was presented for plant cells to convert non-metabolizable phosphite (Phi) to an important phosphate (Pi) for developing cells by gene expression encoding a phosphite oxidoreductase (PTXD) enzyme. The ptxD gene, in combination with a selection medium containing Phi as the sole phosphorus (P) source, can serve as an effective and efficient system for selecting transformed cells. The selection system adds nutrients to transgenic plants without potential risks to the environment. The ptxD/Phi system has been shown to be a promising transgenic selection system with several advantages in cost and safety compared to other antibiotic-based selection systems. In this review, we have summarized the development of selection markers for genetic transformation and the potential use of the ptxD/Phi scheme as an alternative selection marker system to minimize the future use of antibiotic and herbicide marker genes.

scholarly journals Evaluation of a Herbicide-resistant Trait Conferred by the Bar Gene Driven by Four Distinct Promoters in Transgenic Blueberry Plants

2008 ◽  
Vol 133 (4) ◽  
pp. 605-611 ◽  
Author(s):  
Guo-Qing Song ◽  
Kenneth C. Sink ◽  
Peter W. Callow ◽  
Rebecca Baughan ◽  
James F. Hancock
Keyword(s):  
Transgenic Plants ◽  
Herbicide Resistance ◽  
Single Copy ◽  
Vaccinium Corymbosum ◽  
Cauliflower Mosaic Virus ◽  
Leaf Damage ◽  
Marker Genes ◽  
Promoter Strength ◽  
Herbicide Resistant ◽  
Selectable Marker Genes

Four chimeric bialaphos resistance (bar) genes driven by different promoters were evaluated for production of herbicide-resistant ‘Legacy’ blueberry plants (73.4% Vaccinium corymbosum L. and 25% Vaccinium darrowi Camp) through Agrobacterium tumefaciens (Smith & Towns.) Conn.-mediated transformation. When the bars were used as selectable marker genes, different promoters yielded different transformation frequencies. Three chimeric bar genes with the promoter nopaline synthase (nos), cauliflower mosaic virus (CaMV) 35S, or CaMV 34S yielded transgenic plants, whereas a synthetic (Aocs)3AmasPmas promoter did not lead to successful regeneration of transgenic plants. In addition, herbicide resistance in bar-expressing plants was influenced by the promoter strength. Under controlled environmental conditions, 3-month-old plants from six single-copy transgenic events with 35S∷bar or nos∷bar, as well as those nontransgenic plants, were sprayed with herbicide glufosinate ammonium (GS) at five levels (0, 750, 1500, 3000, and 6000 mg·L−1). Evaluations on leaf damage 2 weeks after spraying indicated that all transgenic plants exhibited much higher herbicide resistance than nontransgenic plants. Additionally, the transgenic plants with the 35S∷bar showed a higher herbicide resistance than those with the nos∷bar. After application of 6000 mg·L−1 GS, over 90% of the leaves from plants with the 35S∷bar and 19.5% to 51.5% of the leaves from plants with the nos∷bar showed no symptom of herbicide damage, whereas only 5% of leaves from the nontransgenic had no damage. One-year-old, field-grown plants from four transgenic events with the nos∷bar were evaluated for herbicide resistance after spraying with 750 mg·L−1 GS. Transgenic plants survived with variations in the level of foliar damage; in contrast, all nontransgenic plants died. This study is the first investigation of different promoters for engineering transgenic blueberry plants.

Excision of selectable marker genes from transgenic plants

2002 ◽  
Vol 20 (6) ◽  
pp. 575-580 ◽  
Author(s):  
Peter D. Hare ◽  
Nam-Hai Chua
Keyword(s):  
Transgenic Plants ◽  
Selectable Marker ◽  
Marker Genes ◽  
Selectable Marker Genes

scholarly journals Utility of I-SceI and CCR5-ZFN nucleases in excising selectable marker genes from transgenic plants

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Bhuvan P. Pathak ◽  
Eliott Pruett ◽  
Huazhong Guan ◽  
Vibha Srivastava
Keyword(s):  
Transgenic Plants ◽  
Selectable Marker ◽  
Marker Genes ◽  
Selectable Marker Genes

scholarly journals Construction of Marker-Free Genetically Modified Maize Using a Heat-Inducible Auto-Excision Vector

Genes ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 374 ◽  
Author(s):  
Dengxiang Du ◽  
Ruchang Jin ◽  
Jinjie Guo ◽  
Fangdong Zhang
Keyword(s):  
Transgenic Plants ◽  
Selectable Marker ◽  
Marker Gene ◽  
Transformation Process ◽  
Transgenic Maize ◽  
Vector System ◽  
Marker Genes ◽  
Site Specific ◽  
Selectable Marker Genes ◽  
Marker Free

Gene modification is a promising tool for plant breeding, and gradual application from the laboratory to the field. Selectable marker genes (SMG) are required in the transformation process to simplify the identification of transgenic plants; however, it is more desirable to obtain transgenic plants without selection markers. Transgene integration mediated by site-specific recombination (SSR) systems into the dedicated genomic sites has been demonstrated in a few different plant species. Here, we present an auto-elimination vector system that uses a heat-inducible Cre to eliminate the selectable marker from transgenic maize, without the need for repeated transformation or sexual crossing. The vector combines an inducible site-specific recombinase (hsp70::Cre) that allows for the precise elimination of the selectable marker gene egfp upon heating. This marker gene is used for the initial positive selection of transgenic tissue. The egfp also functions as a visual marker to demonstrate the effectiveness of the heat-inducible Cre. A second marker gene for anthocyanin pigmentation (Rsc) is located outside of the region eliminated by Cre and is used for the identification of transgenic offspring in future generations. Using the heat-inducible auto-excision vector, marker-free transgenic maize plants were obtained in a precisely controlled genetic modification process. Genetic and molecular analyses indicated that the inducible auto-excision system was tightly controlled, with highly efficient DNA excision, and provided a highly reliable method to generate marker-free transgenic maize.

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