Transgenic canola and soybean seeds with increased lysine.

We have increased the lysine content in the seeds of canola and soybean plants by circumventing the normal feedback regulation of two enzymes of the biosynthetic pathway, aspartokinase (AK) and dihydrodipicolinic acid synthase (DHDPS). Lysine-feedback-insensitive bacterial DHDPS and AK enzymes encoded by the Corynebacterium dapA gene and a mutant E. coli lysC gene, respectively, were linked to a chloroplast transit peptide and expressed from a seed-specific promoter in transgenic canola and soybean seeds. Expression of Corynebacterium DHDPS resulted in more than a 100-fold increase in the accumulation of free lysine in the seeds of canola; total seed lysine content approximately doubled. Expression of Corynebacterium DHDPS plus lysine-insensitive E. coli AK in soybean transformants similarly caused several hundred-fold increases in free lysine and increased total sed lysine content by as much as 5-fold. Accumulation of alpha-amino adipic acid (AA) in canola and saccharopine in soybean, which are intermediates in lysine catabolism, was also observed.

Molecular studies on mutations at the Shrunken locus in maize caused by the controlling element Ds.

The structure and expression of the Shrunken (Sh) locus have been examined in several maize strains with mutations at the locus caused by the controlling element Dissociation (Ds). Three of the strains (sh-m6233, sh-m5933, and sh-m6258) are of independent origin, and the fourth (sh-m6795) represents a spontaneous recessive sh allele derived from an Sh revertant of strain sh-m6258. The sh-m6233 and sh-m5933 strains produce undetectable levels of the Sh-encoded sucrose synthetase and very small amounts (less than 1%) of an apparently normal sucrose synthetase mRNA in immature endosperm tissue. Both strains have rearrangements affecting the structure of the locus near the 5' end of the transcription unit. The Sh locus in the related strains sh-m6258 and sh-m6795 is interrupted by an insertion or a rearrangement having one breakpoint in an intervening sequence near the 3' end of the mRNA coding sequence. The 5' end of the gene is transcribed in immature kernels of both mutants, giving aberrant poly (A)+ mRNAs that are homologous to the normal transcript up to the insertion or rearrangement breakpoint and lack homology to the 3' end of the gene. The aberrant transcripts from both strains are translated in vivo and in vitro, yielding 82- and 85-kD proteins that are immunologically related to the 92-kD Sh-encoded sucrose synthetase monomer.