GLUCOSINOLATE METABOLISM IN RAPESEED EMBRYOS - EFFECT OF FEEDING GLUCOSINOLATE PRECURSORS AND UPTAKE OF GLUCOSINOLATE BY DIFFERENT PLANT CULTIVARS

Embryos excised from the developing seed of Brassica napus cultivar Golden were cultured in vitro in the presence of 3-butenyl glucosinolate and desulfo-2-propenyl glucosinolate, potential precursors to the seed glucosinolates 2-hydroxy-3-butenyl and 2-propenyl glucosinolate, respectively. No increase in 2-hydroxy-3-butenyl or in 2-propenyl glucosinolate content was observed in the embryos during the culture period, suggesting that embryos lack the biosynthetic capacity to hydroxylate or to sulfate the 3-butenyl- or desulfo-2-propenyl glucosinolate precursors. Short term uptake experiments demonstrated that benzyl glucosinolate uptake by embryos is competitively inhibited by 3-indolylmethyl glucosinolate, indicating that these two glucosinolate substrates may be served by a common carrier protein. Additionally, glucosinolate uptake by embryos of the high glucosinolate cultivars B. napus Golden and Brassica campestris R500 was compared to uptake by the low glucosinolate cultivars B. napus Westar and B. campestris Tobin. Results indicate that reduced seed glucosinolate content of the low cultivars cannot be attributed to reduced rates of glucosinolate uptake by the embryo. We suggest that reduced amount of glucosinolate in tissues of the maternal plant is responsible for the reduced seed glucosinolate content.