Two feedback-insensitive enzymes of the aspartate pathway in Nicotiana sylvestris

Lysine and threonine overproducer mutants in Nicotiana sylvestris, characterized by an altered regulation of, respectively, dihydrodipicolinate synthase and aspartate kinase activities, were crossed to assess the effects of the simultaneous presence of these genes on the biosynthesis of aspartate-de...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1992-08, Vol.99 (4), p.1285-1293
Main Authors: Frankard, V. (Vrije Universiteit Brussel, Sint-Genesius Rode, Belgium), Ghislain, M, Jacobs, M
Format: Article
Language:English
Subjects:
ACIDE AMINE
ACIDE ASPARTIQUE
ACIDO ASPARTICO
ACTIVIDAD ENZIMATICA
ACTIVITE ENZYMATIQUE
Amino acids
AMINOACIDOS
Biological and medical sciences
BIOSINTESIS
BIOSYNTHESE
Biosynthesis
Enzymes
Fundamental and applied biological sciences. Psychology
Gene expression regulation
GENETICA
GENETIQUE
Heterozygotes
Leaves
LIGASAS
LIGASE
Metabolism
Metabolism and Enzymology
MUTANT
MUTANTES
NICOTIANA
Nitrogen metabolism
Overproduction
Percentages
Phenotypes
Plant physiology and development
Plants
TRANSFERASAS
TRANSFERASE
VIA BIOQUIMICA DEL METABOLISMO
VOIE BIOCHIMIQUE DU METABOLISME
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Summary:Lysine and threonine overproducer mutants in Nicotiana sylvestris, characterized by an altered regulation of, respectively, dihydrodipicolinate synthase and aspartate kinase activities, were crossed to assess the effects of the simultaneous presence of these genes on the biosynthesis of aspartate-derived amino acids. The monogenic dominant behavior of both resistance traits was confirmed, and their loci were found to be unlinked. Study of the inhibition properties of dihydrodipicolinate synthase and aspartate kinase activities in RAEC-1 X RLT 70 confirmed the heterozygote state of both mutations, because only half of their lysine-sensitive activity could still be inhibited by this negative effector. Analysis of the free amino acid pool during the growth of the double mutant revealed a major free lysine overproduction reaching up to 50% of the total pool, whereas the other aspartate-derived amino acids remained equally or even less abundant than in the wild type. An abnormal phenotype was clearly associated with such high levels of lysine accumulation, which points out the possible role of this amino acid in the developmental features of the plant. Comparison of the amino acid content, free and total (free + protein-bound), between the wild type, the two mutants, and the double mutant obtained by crossing them brings new insights on the regulation of the aspartate pathway, and on its implications in relationship to plant nutritional value improvement
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.99.4.1285