BIOSYNTHESIS OF GLUCOSINOLATES IN THE DEVELOPING SILIQUE WALLS AND SEEDS OF SINAPIS-ALBA

When [C-14]tyrosine was administered to developing seeds and silique w alls of Sinapis alba L. both tissues de novo synthesized p-hydroxybenz ylglucosinolate (p-OHBG). Within a silique, the incorporation rate of tyrosine to p-OHBG was up to 70-fold higher in the silique walls compa red to the seeds as evidenced by both in vitro and in vitro measuremen ts. During development, the amount of p-OHBG increases in the seeds, w hereas the level remains relatively constant in the corresponding wall s in radioisotope feeding experiments using intact siliques. This show s that p-OHBG is translocated from the walls to the seeds in S. alba. Although translocation is a major contributor to glucosinolate accumul ation in the seeds, we also demonstrate that seeds of S. alba contain all the enzymes required for de novo biosynthesis of p-OHBG. (C) 1998 Elsevier Science Ltd. All rights reserved.