Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2003
Publication Date: 11/19/2003
Citation: LI, L., THIPYAPONG, P., BREEDEN, D.C., STEFFEN, J.C. OVEREXPRESSION OF A BACTERIAL BRANCHED-CHAIN ALPHA-KETO ACID DEHYDROGENASE COMPLEX IN ARABIDOPSIS RESULTS IN ACCUMULATION OF BRANCHED-CHAIN ACYL-COAS AND ALTERATION OF FREE AMINO ACID COMPOSITION IN SEEDS. PLANT SCIENCE. 2003. v. 165. p. 1213-1219. Interpretive Summary: Genetic engineering of agronomic traits or manipulation of complex metabolic pathways in plants requires introduction and expression of multiple genes into plants. In this study, we used branched-chain alpha-keto acid dehydrogenase (BCKDH), a multienzyme complex composing of four genes, as an example to introduce multigenes into plant by a single transformation event. The BCKDH enzyme complex catalyzes the degradation of branched-chain amino acids and results in the formation of branched-chain acyl-CoAs. The branched-chain acyl-CoAs provide metabolic precursors for the formation of acyl-sugars, which contribute to insect resistance in a number of plant species and can be used for the biosynthesis of biodegradable plastics.
Technical Abstract: Branched-chain alpha-keto acid dehydrogenase (BCKDH) is a multienzyme complex that plays an important role in branched-chain amino acid catabolism. It occupies a key position in intermediary metabolism and provides metabolic precursors for secondary metabolism. Multigenes encoding a bacterial BCKDH were introduced and overexpressed in Arabidopsis. The transgenic plants expressed an over 7-fold increase of BCKDH activity in seeds than control plants and accumulated significant high levels of branched-chain acyl-CoAs. Overexpression of the BCKDH complex also resulted in alternation of free amino acid composition in seeds with enhanced levels of branched-chain amino acids. These results demonstrate that it is possible to elevate the branched-chain acyl-CoA levels in providing the metabolic precursors for potential genetic and metabolic engineering of plants for agricultural and industrial purposes.