1. Characterization of monofunctional aspartate kinase genes in maize and their relationship with free amino acid content in the endosperm
- Author
-
Jose A. Lopez-Valenzuela, Bryan C. Gibbon, Brian A. Larkins, Xuelu Wang, Gad Galili, and Bertrand Gakière
- Subjects
Physiology ,Molecular Sequence Data ,Quantitative Trait Loci ,Plant Science ,Biology ,Zea mays ,chemistry.chemical_compound ,Sequence Analysis, Protein ,Aspartate kinase ,Amino Acid Sequence ,Aspartate Kinase ,Threonine ,Amino Acids ,Cloning, Molecular ,Amino acid synthesis ,Alleles ,Plant Proteins ,Homoserine dehydrogenase ,chemistry.chemical_classification ,Methionine ,Genetic Complementation Test ,Chromosome Mapping ,Sequence Analysis, DNA ,Amino acid ,chemistry ,Biochemistry ,Seeds ,Isoleucine ,Leucine ,Sequence Alignment - Abstract
A quantitative trait locus has previously been identified in maize (Zea mays L.) that influences the level of free amino acids in the endosperm, especially those from the aspartate pathway: lysine, threonine, methionine, leucine, and isoleucine. Because this locus occurs in a region of the genome containing ask2, a monofunctional aspartate kinase, the nature of the monofunctional aspartate kinase genes in the parental inbreds, Oh545o2 and Oh51Ao2, was investigated. Two genes, Ask1 and Ask2 were isolated, and Ask2 was mapped to the ask2 locus. Nucleotide sequence analysis of the Ask2 alleles from Oh545o2 and Oh51Ao2 showed they differ by one amino acid. Both alleles complemented a yeast aspartate kinase mutant, hom3, and based on the growth of the yeast mutant it appeared that Ask2-Oh545o2 produces an enzyme with greater total activity than that encoded by the Oh51Ao2 allele. The results suggest that the higher level of free amino acids derived from the aspartate pathway in Oh545o2 endosperm results from a single amino acid change in the ASK2 enzyme that has pleiotropic effects on its activity.
- Published
- 2007