Selectable marker genes (SMGs) and selection agents are useful tools in the production of transgenic plants. Most SMGs express protein products that confer antibiotic- or herbicide resistance traits, and typically reside in the end product of genetically modified (GM) plants. The presence of marker genes in their genomes becomes useless and their effects become unpredictable or even potentially dangerous. In recent years, several strategies have been developed to remove SMGs from GM products while retaining the transgenes of interest. This article describes the existing strategies for SMG removal, including the implementation of recently developed techniques like Mega-nuclease, TALENs, ZFNs and CRISPR.
The systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals. The resistance that developed in the distal, untreated portion of pathogen inoculated plants is termed as systemic acquired resistance