אסיף מאגר המחקר החקלאי

Enhanced levels of free and protein-bound threonine in transgenic alfalfa (Medicago sativa L.) expressing a bacterial feedback-insensitive aspartate kinase gene

Year:

2000

Source of publication :

Authors :

Volume :

9

Co-Authors:

Galili, S., Agronomy/Nat. Research Department, Agricultural Research Organization, (Volcani Center), Bet Dagan 50250, Israel, Institute of Field and Garden Crops, Agriculture Research Organization, (Volcani Center), P.O.B. 6, Bet-Dagan 50250, Israel
Guenoune, D., Agronomy/Nat. Research Department, Agricultural Research Organization, (Volcani Center), Bet Dagan 50250, Israel
Wininger, S., Agronomy/Nat. Research Department, Agricultural Research Organization, (Volcani Center), Bet Dagan 50250, Israel
Hana, B., Agronomy/Nat. Research Department, Agricultural Research Organization, (Volcani Center), Bet Dagan 50250, Israel
Schupper, A., Plant Sciences Department, Weizmann Institute of Science, Rehovot 76100, Israel
Ben-Dor, B., Agronomy/Nat. Research Department, Agricultural Research Organization, (Volcani Center), Bet Dagan 50250, Israel
Kapulnik, Y., Agronomy/Nat. Research Department, Agricultural Research Organization, (Volcani Center), Bet Dagan 50250, Israel

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Abstract:

Threonine, lysine, methionine, and tryptophan are essential amino acids for humans and monogastric animals. Many of the commonly used diet formulations, particularly for pigs and poultry, contain limiting amounts of these amino acids. One approach for raising the level of essential amino acids is based on altering the regulation of their biosynthetic pathways in transgenic plants. Here we describe the first production of a transgenic forage plant, alfalfa (Medicago sativa L.) with modified regulation of the aspartate-family amino acid biosynthetic pathway. This was achieved by over-expressing the Escherichia coli feedback-insensitive aspartate kinase (AK) in transgenic plants. These plants showed enhanced levels of both free and protein-bound threonine. In many transgenic plants the rise in free threonine was accompanied by a significant reduction both in aspartate and in glutamate. Our data suggest that in alfalfa, AK might not be the only limiting factor for threonine biosynthesis, and that the free threonine pool in this plant limits its incorporation into plant proteins.

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