Marker Gene Elimination from Transgenic Sugarbeet by a Chemically Regulated Cre-lox System

Abstract

The absence of selection markers is a highly desired feature of transgenic crops considering market acceptance but also to enable multiple transformation. However, the current strategies for obtaining marker-free plants either require time consuming sexual crosses or depend on highly efficient transformation protocols (Hohn et al., 2001) which are either not preferred or not available for sugarbeet. Recently, Zuo et al. (2001) developed a chemical-regulated marker elimination system in Arabidopsis with which marker-free transgenic plants may be obtained directly from in vitro culture. This system is based on the introduction of an XVE inducible system for controlling cre-lox-mediated recombination. The marker elimination process is initiated by the addition of an external inducer (estradiol) which activates the estrogen receptor-based fusion transactivator XVE. This consequently enables the expression of cre, resulting in the excision of the marker gene flanked by two lox sites through recombination. We report here of the successful application of this chemical-regulated cre-lox marker elimination system in sugarbeet.