title: Different elongation pathways in the biosynthesis of acyl groups of trichome exudate sugar esters from various solanaceous plants.
abstract: Two common pathways are known for elongation of aliphatic acids via acetate in biological organisms: the fatty acid synthase (FAS) and the alpha-ketoacid elongation (alphaKAE) pathways. The alphaKAE route is utilized in many biosynthetic pathways, including the tricarboxylic acid cycle, leucine biosynthesis, and in formation of coenzyme B, glucosinolates, alpha-ketoadipate, sugar-ester acyl acids, short-chain alcohols of yeast and Clostridium species, 2-amino-4-methylhex-4-enoic acid, and l-gamma-phenyl butyrine. In the FAS route, both carbons from acetyl-acyl carrier protein are retained per elongation cycle, while in the alphaKAE route only one carbon from acetyl-coenzyme A is retained. Available evidence indicates that different members of the family Solanaceae may use one or the other of these elongation mechanisms in the synthesis of acyl groups of trichome-exuded sugar esters. In both, precursors for elongation are derived from branched-chain amino acid metabolism. Here we compared radiolabeling patterns in sugar-ester acyl groups from trichomes (the specific tissue in which sugar esters are synthesized) of the tobaccos, Nicotiana benthamiana, N. gossei, N. glutinosa, of Petunia x hybrida cv. Falcon Red & White, and Datura metel, and epidermal peels of Lycopsersicon pennellii after their synthesis from [2-(14)C]-, [1-(14)C]- and [1,2-(14)C]acetate. Recovered acyl acids were purified and then degraded to determine label distribution between the carboxyl termini and the remainder of the molecules. Six- and 20-h incubations were studied, and membrane fatty acids were monitored as internal controls for FAS-mediated elongation. Results are consistent with participation of alphaKAE in synthesis of sugar-ester acyl groups of tobaccos and petunia, but apparently FAS is utilized in the formation of these groups in L. pennellii and D. metel.
authors.affiliation: Plant Physiology/Biochemistry/Molecular Biology Program, Agronomy Department, University of Kentucky, Lexington, KY 40546-0236, USA.
authors.forename: Antoaneta B
authors.initials: AB
authors.lastname: Kroumova
authors.forename: George J
authors.initials: GJ
authors.lastname: Wagner
mesh_terms: D064429:Fatty Acid Synthases / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D019657:Solanaceae / Q000201:enzymology / Q000378:metabolism*; D013045:Species Specificity; D013395:Sucrose / Q000031:analogs & derivatives* / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D013395:Sucrose; D064429:Fatty Acid Synthases