Recent advances in development of marker-free transgenic plants: Regulation and biosafety concern

Abstract

During the efficient genetic transformation of plants with the gene of interest, some selectable marker genes are also used in order to identify the transgenic plant cells or tissues. Usually, antibiotic- or herbicide-selective agents and their corresponding resistance genes are used to introduce economically valuable genes into crop plants. From the biosafety authority and consumer viewpoints, the presence of selectable marker genes in released transgenic crops may be transferred to weeds or pathogenic microorganisms in the gastrointestinal tract or soil, making them resistant to treatment with herbicides or antibiotics, respectively. Sexual crossing also raises the problem of transgene expression because redundancy of transgenes in the genome may trigger homology-dependent gene silencing. The future potential of transgenic technologies for crop improvement depends greatly on our abilities to engineer stable expression of multiple transgenic traits in a predictable fashion and to prevent the transfer of undesirable transgenic material to non-transgenic crops and related species. Therefore, it is now essential to develop an efficient marker-free transgenic system. These considerations underline the development of various approaches designed to facilitate timely elimination of transgenes when their function is no longer needed. Due to the limiting number of available selectable marker genes, in future the stacking of transgenes will be increasingly desirable. The production of marker-free transgenic plants is now a critical requisite for their commercial deployment and also for engineering multiple and complex trait. Here we describe the current technologies to eliminate the selectable marker genes (SMG) in order to develop marker-free transgenic plants and also discuss the regulation and biosafety concern of genetically modified (GM) crops.

Generating Marker-Free Transgenic Wheat Using Minimal Gene Cassette and Cold-Inducible Cre/Lox System

“…Cre/lox auto-excision system was successfully applied for eliminating the undesirable parts of the transformation vectors as the selection marker gene, in many species (Gidoni et al 2008;Tuteja et al 2012). For the induction of cre, in auto-excision strategy, many types of promoters have already been tested with different efficiency (Chakraborti et al 2008;ChongPerez et al 2012ChongPerez et al , 2013Russell et al 1992).…”

7. Themenbereich grüne Gentechnologie: Pflanzenzüchtung und Agrarwirtschaft

“…Gerade beim "trait stacking" kommt der Entfernung der verwendeten Selektionsmarker eine besondere Bedeutung zu (siehe Kapitel 7.2.6), da es in aufeinanderfolgenden Selektionsschritten sonst zu einer Anreicherung der verschiedenen Marker im Genom führen kann (Tuteja et al, 2012).…”

“…Auch die komplexen Wechselwirkungen zwischen molekulargenetischen Faktoren und der Umwelt, die die Genexpression beeinflussen, können aufgedeckt werden, wenn "genetical genomics"-Studien unter unterschiedlichen Umweltbedingungen wiederholt werden (Snoek et al, 2013;Joosen et al, 2013 lung (Schatten) zu Genotyp-Umwelt-Interaktionen führte, die mit einer veränderten Genexpression in bestimmten Genregionen einhergingen (Snoek et al, 2013 Die Anzahl an selektierbaren Markern, die nicht auf einer Antibiotikum-oder Herbizidresistenz beruhen, hat im Untersuchungszeitraum beträchtlich zugenommen. Inzwischen sind für Pflanzen bereits mehr als 50 Markergene beschrieben worden (Manimaran et al, 2011;Rosellini, 2011;Tuteja et al, 2012). 48 Neben der Verwendung alternativer Markergene kommt auch der Erzeugung markerfreier transgener Pflanzen eine steigende Bedeutung zu.…”

Genetic engineering of crops: a ray of hope for enhanced food security

“…Production of marker-free transgenic crops to avoid the risk of horizontal gene transfer, e.g., antibiotic resistance genes from genetically engineered crops to soil-and plant-related microorganisms or escape of herbicide resistant genes to wild relatives also needs the attention of plant scientists. 20,21 Furthermore, stress-inducible promoters, which only express when exposed to stresses, have also been identified with minimum negative effects on the plant growth. Genetic engineering of plants for abiotic stress tolerance with stressinducible promoters has uncovered the way ahead for abiotic stress tolerance without yield penalty.…”