REDIRECTION OF TRYPTOPHAN LEADS TO PRODUCTION OF LOW INDOLE GLUCOSINOLATE CANOLA

Cruciferous plants are known to produce over a hundred different musta rd oil glycosides, which are derived from methionine, phenylalanine, o r tryptophan. In oil-producing crops like Brassica napus (canola), the presence of indole glucosinolates in seed protein meals has decreased meal palatability and has limited their value as animal feed. We have transformed canola plants with a gene that encodes tryptophan decarbo xylase (TDC) in an attempt to redirect tryptophan into tryptamine rath er than into indole glucosinelates. Transgenic plants that expressed t his decarboxylase activity accumulated tryptamine while correspondingl y lower levels of tryptophan-derived indole glucosinolates were produc ed in all plant parts compared with nontransformed controls. Of partic ular significance, the indole glucosinolate content of mature seeds fr om transgenic plants was only 3 % of that found in nontransformed seed s. These results demonstrate how the creation of artificial metabolic sinks could divert metabolite flow and be used to remove these undesir able indole glucor sinolates, thereby increasing the value of the oils eed meals, which are produced after extraction of oil from the seed.