Chlorsulfuron modifies biosynthesis of acyl acid substituents of sucrose esters secreted by tobacco trichomes

• Published in: Plant physiology (Bethesda) Vol. 94; no. 3; pp. 906 - 912
• Main Authors: Kandra, L. (University of Kentucky, Lexington, KY), Wagner, G.J
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.11.1990
• Subjects: ACIDE AMINE; Agronomy. Soil science and plant productions; Amino acid metabolism; AMINOACIDOS; Biological and medical sciences; BIOSINTESIS; BIOSYNTHESE; Biosynthesis; Chemical control; Enzymes; ESTER; ESTERES; Esters; Fundamental and applied biological sciences. Psychology; HERBICIDAS; HERBICIDE; Herbicides; Keto acids; Metabolism and Enzymology; METABOLISME; METABOLISMO; NICOTIANA TABACUM; Parasitic plants. Weeds; PELOS VEGETALES; Phytopathology. Animal pests. Plant and forest protection; Plants; POIL VEGETAL; Product labeling; Radiocarbon; SACCHAROSE; SUCROSA; TECHNIQUE DES TRACEURS; TECNICAS DE TRAZADORES; Trichomes; VIA BIOQUIMICA DEL METABOLISMO; VOIE BIOCHIMIQUE DU METABOLISME; Weeds; Sucrose; Enzyme inhibitor; Synthetic inhibitor; Nicotiana tabacum; Trichome; Herbicide; Ester; Dicotyledones; Angiospermae; Sulfonylureas; Acetolactate synthase; Spermatophyta; Solanaceae; Ketoacid; Mechanism of action; Acylation
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.94.3.906

Sucrose esters and duvatrienediol diterpenes are principal constituents formed in and secreted outside head cells of trichomes occurring on surfaces of Nicotiana tabacum. Using trichome-bearing epidermal peels prepared from midveins of N. tabacum cv T.I. 1068 leaves, we found that chlorsulfuron reduced and modified radiolabeling of sucrose ester acyl acids derived from branched-chain amino acid metabolism. The herbicide did not effect formation and exudation of diterpenes which are products of isoprenoid metabolism. Treatment with 1.0 micromolar chlorsulfuron affected 8.5- and 6.3-fold reductions in radiolabeling of methylvaleryl and methylbutyryl groups of sucrose esters, respectively, and concomitant increases of 9- and 9.8-fold in radiolabeling of straight chain valeryl and butyryl groups, respectively. These results and others indicate that inhibition of acetolactate synthase causes an accumulation of 2-oxo-butyric acid that is utilized by enzymes common to Leu biosynthesis to form 2-oxo-valeric acid. Coenzyme A (CoA) activation of this keto acid gives rise to butyryl CoA, which is utilized to form butyryl containing sucrose esters. Alternatively, reutilization of 2-oxo-valeric acid by the same enzymes followed by CoA activation leads to valeryl containing sucrose esters. We propose that in trichome secretory cells synthase, isomerase and dehydrogenase enzymes which catalyze Leu synthesis/degredation in most tissues, convert iso-branched, anteiso-branched and straight-chain keto acids in the formation of sucrose ester acyl groups