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Title: Structural and transcriptional analysis of plant genes encoding the bifunctional lysine ketoglutarate reductase saccharopine dehydrogenase enzyme

Author
item Anderson, Olin
item COLEMAN-DERR, DEVIN - University Of California
item Gu, Yong
item HEATH, SEKOU - University Of California

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2010
Publication Date: 6/16/2010
Citation: Anderson, O.D., Coleman-Derr, D., Gu, Y.Q., Heath, S. 2010. Structural and transcriptional analysis of plant genes encoding the bifunctional lysine ketoglutarate reductase saccharopine dehydrogenase enzyme. Biomed Central (BMC) Genomics. 10:113.

Interpretive Summary: Humans, along with other monogastric animals, depend on external dietary sources for half of the different amino acids needed for protein synthesis. Among those essential amino acids, the most severely limiting in the cereals is lysine. Since cereals make up half of the human diet, lysine limitation has quality/nutritional consequences – including limitations on wheat, the most widely grown crop on earth and the single greatest source of amino acids in the human diet. Lysine synthesis, along with the synthesis of the essential amino acids threonine and methionine, is controlled by the aspartate-family pathway. This anabolic pathway is in turn influenced by the lysine degradation pathway controlled mainly by the catabolic bifunctional enzyme lysine ketoglutarate reductase – saccharopine dehydrogenase (LKR/SDH). In addition to lysine metabolism, this gene has been implicated in a number of important metabolic and developmental pathways. The analysis of a wheat LKR/SDH gene and comparative structural and functional analyses among available plant genes provides new information on this important gene. Both the structure of the LKR/SDH gene and the immediately adjacent genes show lineage-specific differences between monocots and dicots, and findings suggest variation in activity of LKR/SDH genes among plants. Functional activity of this gene is presented along with evidence of different types of activity in different grasses.

Technical Abstract: The analysis of a wheat lysine ketoglutarate reductase – saccharopine dehydrogenase (LKR/SDH) gene and comparative structural and functional analyses among available plant genes provides new information on this important gene. Both the structure of the LKR/SDH gene and the immediately adjacent genes show lineage-specific differences between monocots and dicots, and findings suggest variation in activity of LKR/SDH genes among plants. One of the adjacent genes in wheat is not present in other plants and may be unique to the Triticeae. Although most plant genomes seem to contain a single conserved LKR/SDH gene per genome, poplar possesses multiple contiguous genes. A preponderance of SDH transcripts suggests the LKR region may be more rate-limiting. The differences among plants for both bifunctional and monofunctional transcripts suggest differential effects on plant metabolism. Only switchgrass has EST evidence for LKR monofunctional transcripts - transcripts that read into an intron of the full-length sequence. Evidence for monofunctional SDH transcripts shows a novel intron composed of a central portion of an intron in the full-length LKR/SDH gene for wheat, Brachypodium, and poplar.