Abstract: A bifunctional enzyme has been isolated and purified from carrots which has both aspartokinase and homoserine dehydrogenase activities in the same polypeptide. The enzyme can be used to regulate lysine, homoserine, threonine, isoleucine and methionine content in plants. The DNA sequence encoding the bifunctional enzyme is also disclosed.

Abstract: Plant germplasm is transformed with foreign DNA by introducing the DNA into pollen grains by a technique such as electroporation, mating ova of the desired plant line with the transformed pollen, and selecting for the transformed germplasm. The germinating pollen, resultant seed, and the progeny can each be screened for expression of the foreign gene. The transformed pollen can be used as a vector for introducing the foreign DNA into plant lines of similar or dissimilar origin, including both monocots and dicots.

Abstract: An isolated and purified bifunctional protein from carrots with aspartokinase and homoserine activities which can be used to regulate the amino acid content of plants, in particular the lysine, homoserine, threonine, isoleucine and/or methionine content is disclosed. In addition, a DNA molecule with a DNA sequence coding for a homologous segment of the bifunctional carrot protein is also disclosed. In a method of regulating the amino acid content in a plant by bringing an effective amount of the bifunctional protein in contact with the plant is disclosed.