IMPROVEMENT IN THE QUALITY OF SEED STORAGE PROTEIN BY TRANSFORMATION OF BRASSICA-NAPUS WITH AN ANTISENSE GENE FOR CRUCIFERIN

The levels of certain essential amino acids, in particular cysteine, l ysine and methionine, in the seed storage protein of a commercial spri ng variety of rape, Brassica napus, have been increased by the introdu ction of an antisense gene for cruciferin, which is the most abundant storage protein in rapeseed. The antisense construct contained part of the cruA gene in an inverted orientation, and the gene was driven by the 5' flanking region of the gene for napin such that antisense RNA w as expressed in a seed-specific manner. The construct was introduced b y Agrobacterium-mediated gene transfer. In self-pollinated seeds (T1 s eeds) of transgenic plants there was a reduction in the levels of the alpha 1 beta 1 and alpha 2/3 beta 2/3 subunits of cruciferin, whereas the level of the alpha 4 beta 4 subunit was unchanged. The total prote in and lipid contents of transgenic seeds did not differ significantly from that of normal seeds. Seeds with reduced amounts of cruciferin a ccumulated higher amounts of napin than non-transformed seeds, but the level of oleosin was unaffected. Amino-acid analysis of the seed stor age protein revealed that T1 seeds with reduced amounts of cruciferin contained higher relative levels of three essential amino acids, namel y, lysine, methionine and cysteine, with increases of 10%, 8% and 32% over the respective levels in non-transgenic seeds (B. napus cv Westar ).