ARS | Publication request: Cloning and expression of genes of aspartate-family amino acid aiosynthesis from medicago truncatula

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2010
Publication Date: July 2, 2010
Citation: Mills, W.R., Grusak, M.A., Hong, S-B., Stephens, B.S. 2010. Cloning and expression of genes of aspartate-family amino acid biosynthesis from medicago truncatula [abstract]. Vth International Congress on Legume Genetics and Genomics. p. 116.

Technical Abstract: Four of the amino acids that must be acquired in the human diet, lysine, threonine, methionine and isoleucine, are derived from a common precursor, aspartate, and are produced in a branched, highly-regulated, biosynthetic pathway. Moreover, the common dietary sources of plant proteins, cereals grains and legume seeds, do not alone provide a complete source of essential amino acids; for example, cereals have relatively low concentrations of lysine, and threonine, and legume seeds have low concentration of methionine. Thus, there has been longstanding interest in understanding factors influencing concentrations of essential amino acids and protein in plants with the hope of using this information to increase the levels of the essential amino acid in agricultural crops. Toward that aim, we have initiated a project to clone the genes of aspartate-family amino acid biosynthesis in the model legume, Medicago truncatula. RNA was isolated from leaf tissues; then, cDNA was synthesized and used as a template for PCR amplification with gene-specific primers derived from M. truncatula BAC clone sequences in GenBank that were analyzed by FGENESH. The PCR products were then gel purified, TA cloned and sequenced. Based on sequence analysis, putative genes for the following aspartate-family enzymes have been cloned: bifunctional aspartate kinase-homoserine dehydrogenase, monofunctional aspartate kinase, monofunction homoserine dehydrogenase, cystathionine-gamma-synthase, methionine synthase, and threonine synthase. Protein expression and functional analysis studies of these clones are underway and results from the studies will be presented. The goal is to use the information from the current research to carry out further studies in the model legume, M. truncatula that may provide insight into amino acid biosynthesis in legume crops.