Plants produce defence compounds as a protection against pests. Glucosinolates are such compounds which are toxic not only to pests, but also to animals and humans. According to Halkier et al. 2012, defence compounds are translocated to seeds using two members of the nitrate/peptide transporter family, GTR1 and GTR2, as glucosinolate-specific transporters in Arabidopsis. 
The authors found that the gtr1 gtr2 double mutant did not accumulate glucosinolates in seeds and had more than tenfold over-accumulation in source tissues such as leaves and silique walls. It is therefore being suggested that GTR1 and GTR2 control the transport of glucosinolates to the seeds of oil plants such as rape. Rapeseed cake, which is a by-product of rape oil, may be used as feed by pig and chicken farmers. Toxin-free oilseed rape could become a feed crop, reducing the dependence of soy cake for animal feed.
The authors try to produce oilseed rape which lack the GTR1 and GTR2 proteins resulting in seeds completely free of glycosinolates.
 Nour-Eldin HH, Andersen TG, Burow M, Madsen SR, Jørgensen ME, Carl Erik Olsen , Dreyer I, Hedrich R, Geiger D, Halkier BA: NRT/PTR transporters are essential for translocation of glucosinolate defence compounds to seeds. Nature August 5, 2012. Doi:10.1038/nature11285