A T-DNA Insertion Knockout of the Bifunctional Lysine-Ketoglutarate Reductase/Saccharopine Dehydrogenase Gene Elevates Lysine Levels in Arabidopsis Seeds

• Published in: Plant physiology (Bethesda) 2001-08, Vol.126 (4), p.1539-1545
• Main Authors: Zhu, Xiaohong, Tang, Guiliang, Granier, Fabienne, Bouchez, David, Galili, Gad
• Format: Article
• Language: English
• Subjects: Albumins; Amino acids; Arabidopsis; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - metabolism; Base Sequence; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; Catabolism; Dehydrogenase; Deoxyribonucleic acid; DNA; DNA, Bacterial - genetics; Essential amino acids; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene expression regulation; Genes, Plant; Genetic loci; Genetics; Globulins; Growth conditions; Homozygote; ketoglutarate reductase; LDK gene; Life Sciences; LKR gene; Lysine - metabolism; Metabolism; Models, Molecular; Molecular Sequence Data; Mutation; Nitrogen metabolism; Phenotype; Plant physiology and development; Plants; Plants genetics; Polymerase chain reaction; saccharopine dehydrogenase; Saccharopine Dehydrogenases - genetics; Saccharopine Dehydrogenases - metabolism; SDH gene; Seeds; Seeds - enzymology; Seeds - genetics; Seeds - metabolism
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.126.4.1539

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.