Poster: Lipids & Related Molecules
Abs #
869: Studies of a-ketoacid elongation: A mechanism for elongation of short and medium chain length, branched and un-branched fatty acids in plants
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Presenter: |
Mihaylova-Kroumova, Antoaneta B, amihaylo@uky.edu |
Authors | Mihaylova-Kroumova, Antoaneta B (A) Wagner, George J (A) | | Affiliations: |
(A): Plant Physiology/Biochemistry/Molecular Biology Program, Agronomy Dept., University of Kentucky, Lexington, KY 40546-0091, U.S.A.
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| Web Site: | http://www.uky.edu/~gjwagn2 | |
Short and medium chain length fatty acids and their derivatives contribute substantially to flavors and aromas of plant foods and fragrances, and to many commercial flavors and fragrances. Yet, the pathways for biosynthesis of these often low-abundance compounds are poorly understood. Two common mechanisms are known for elongation of such aliphatic acids via acetate in biological organisms: the fatty acid synthase (FAS) and a-ketoacid elongation (aKAE) pathways. The aKAE mechanism is utilized in many biosynthetic pathways, including the TCA cycle, leucine biosynthesis, formation of Coenzyme B, glucosinolates, a-ketoadipate, sugar ester acyl acids and 2-amino-4-methylhex-4-enoic acid. In the FAS pathway, both carbons from acetyl-ACP are retained per elongation cycle, while in aKAE only one carbon from acetyl-CoA is retained. Different members of the family Solanaceae may use one or the other of these elongation mechanisms in the synthesis of acyl groups of trichome-exudated sugar esters. But, there is controversy over this question. Precursors for elongation are derived from branched chain amino acid metabolism. Here we compared radiolabeling patterns in sugar ester acyl groups from tobaccos, petunia and Datura trichomes, and tomato epidermal peels to assess the possible roles of FAS or aKAE in acyl group formation. Results are consistent with participation of aKAE in synthesis of sugar ester acyl groups of tobaccos and petunia, but FAS in formation of these groups in Lycopersicon pennellii and Datura metel. Knockdown of a tomato isopropylmalate synthase gene - a key component of branched chain amino acid synthesis - in tomato and tobacco, using RNAi, impacts sugar ester acyl group composition and plant growth and development.
