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Plant Physiol, August 2001, Vol. 126, pp. 1539-1545
A T-DNA Insertion Knockout of the Bifunctional
Lysine-Ketoglutarate Reductase/Saccharopine Dehydrogenase Gene Elevates
Lysine Levels in Arabidopsis Seeds1
Xiaohong
Zhu,
Guiliang
Tang,
Fabienne
Granier,
David
Bouchez, and
Gad
Galili*
Department of Plant Genetics, The Weizmann Institute of Science,
Rehovot 76100 Israel (X.Z., G.T., G.G.); and Laboratoire de Biologie
Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles, France (F.G., D.B.)
Plants possess both anabolic and catabolic pathways for the
essential amino acid lysine (Lys). However, although the biosynthetic pathway was clearly shown to regulate Lys accumulation in plants, the
functional significance of Lys catabolism has not been experimentally elucidated. To address this issue, we have isolated an Arabidopsis knockout mutant with a T-DNA inserted into exon 13 of the gene encoding
Lys ketoglutarate reductase/saccharopine dehydrogenase. This
bifunctional enzyme controls the first two steps of Lys catabolism. The
phenotype of the LKR/SDH knockout was indistinguishable
from wild-type plants under normal growth conditions, suggesting that Lys catabolism is not an essential pathway under standard growth conditions. However, mature seeds of the knockout mutant
over-accumulated Lys compared with wild-type plants. This report
provides the first direct evidence for the functional significance of
Lys catabolism in regulating Lys accumulation in seeds. Such a knockout
mutant may also provide new perspectives to improve the level of the essential amino acid Lys in plant seeds.
1
This work was supported by grants from the
FrameWork Program of the Commission of the European Communities, and
the Israel Academy of Sciences and Humanities, National Council for
Research and Development, Israel. G.T. was supported in part by a Leon and Kathe Fallek scholarship. G.G. is an incumbent of the Bronfman Chair of Plant Sciences.
*
Corresponding author; e-mail gad.galili{at}weizmann.ac.il; fax
972-8-9344181.
© 2001 American Society of Plant Physiologists
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