Green fluorescent protein as a marker for expression of a second gene in transgenic plants

The use of transgenic crops has generated concerns about transgene movement to unintended hosts and the associated ecological consequences. Moreover, the in-field monitoring of transgene expression is of practical concern (e. g., the underexpression of an herbicide tolerance gene in crop plants that are due to be sprayed with herbicide). A solution to these potential proble ms is to monitor the presence and expression of an agronomically important gene by linking it to a marker gene, such as GFP. Here we show that GFP flu orescence can indicate expression of the Bacillus thuringiensus cry1Ac gene when co-introduced into tobacco and oilseed rape, as demonstrated by insec t bioassays and western blot analysis. Furthermore we conducted two seasons of field experiments to characterize the performance of three different GF P genes in transgenic tobacco. The best gene tested was mGFP5er, a mutageni zed GFP gene that is targeted to the endoplasmic reticulum. We also demonst rated that host plants synthesizing GFP in the field suffered no fitness co sts.