STABLE EXPRESSION OF THE SULFUR-RICH 2S ALBUMIN GENE IN TRANSGENIC VICIA-NARBONENSIS INCREASES THE METHIONINE CONTENT OF SEEDS

Both the narbon bean (Vicia narbonensis) and tobacco plants were trans formed using Agrobacterium tumefaciens strains containing binary vecto rs with the gene coding for the methionine-rich 2S albumin of Brazil n uts under the control of either the Cauliflower Mosaic Virus 35S promo ter or the legumin B4 promoter from V. faba. Stable integration in the genome was verified by both Southern blotting and segregation analysi s. Under the control of the viral promoter, 2S albumin was produced in a variety of tissues at a relatively low level in both species. The L eB4 promoter conferred seed-specific high level expression in V. narbo nensis and low level seed-specific expression in tobacco. A total of 5 0 independent transgenic narbon bean lines containing the LeB4-2S albu min construct have so far been isolated. Eighteen of these lines were further characterised and several stable homozygous lines established. Comparisons of homozygous and heterozygous progeny in these strains r evealed that a doubling of the number of genes resulted in an approxim ate doubling in the amount of gene product. The absolute protein level s reached varied between lines. Amino acid analysis revealed an approx imate 3 fold increase in the methionine content of seed protein in one Ro line. Further analysis of these lines is aimed at determining how to achieve high level production of foreign proteins in seeds and more specifically at improving the nutritional quality of the seed protein of legumes.