Two common pathways are known for elongation of aliphatic acids via acetate in biological organisms: the fatty acid synthase (FAS) and the a-ketoacid elongation (aKAE) pathways. The aKAE route is utilized in many biosynthetic pathways, including the tricarboxylic acid cycle, leucine biosynthesis, and in formation of coenzyme B, glucosinolates, a-ketoadipate, sugar-ester acyl acids, short-chain alcohols of yeast and Clostridium species, 2-amino-4-methylhex-4-enoic acid, and L-c-phenyl butyrine. In the FAS route, both carbons from acetyl-acyl carrier protein are retained per elongation cycle, while in the aKAE 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 trichomeexuded sugar esters. In both, precursors for elongation are derived from branched-chain amino acid metabolism. Here we compared radiolabeling patterns in sugarester acyl groups from trichomes (the specific tissue in which sugar esters are synthesized) of the tobaccos, Nicotiana benthamiana, N. gossei, N. glutinosa, of Petunia · 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 aKAE 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.

Pathways and enzymes offatty acid synthasemediated, long-even-chain (generally C16-C20) fatty add synthesis are well studied, and general metabolism involved in short-chain (Cs-C7) fatty acid biosynthesis is also understood.In contrast, mechanism of medinm-chain (C#-C14) Mechanisms for synthesis oflong-chain fatty acids (lcFAs) in plants are well studied (1). In contrast, metabolism leading to the biosynthesis of mcFAs is not well understood (4, 5), particularly that catalyzing the formation of branched and odd-length mcFAs. Straight, iso-, and antiso-branched, oddand even-length scFAs are synthesized via modified branched-chain amino acid (bcAA) metabolism in tobacco

A unique feature of glandular trichomes of plants in the botanical family Solanaceae is that they produce sugar esters (SE), chemicals that have been shown to possess insecticidal, antifungal, and antibacterial properties. Sugar esters of tobacco (Nicotiana tabacum) provide pest resistance, and are important flavor precursors in oriental tobacco cultivars. Acyl moieties of SEs in Nicotiana spp., petunia, and tomato are shown to vary with respect to carbon length and isomer structure (2-12 carbon chain length; anteiso-, iso-, and straight-chain). Sugar esters and their acyl groups could serve as a model to explore the basis of phenotypic diversity and adaptation to natural and agricultural environments. However, information on the diversity of acyl composition among species, cultivars, and accessions is lacking. Herein, described is the analysis of SE acyl groups found in 21 accessions of Nicotiana obtusifolia (desert tobacco), six of Nicotiana occidentalis subsp. hesperis, three of Nicotiana alata, two of N. occidentalis, four modern tobacco cultivars, five petunia hybrids, and one accession each of a primitive potato (Solanum berthaultii) and tomato (Solanum pennellii). A total of 20 different acyl groups was observed that were represented differently among cultivars, species, and accessions. In Nicotiana species, acetate and iso- and anteiso-branched acids prevailed. Straight-chain groups (2-8 carbons) were prominent in petunias, while octanoic acid was prominent in N. alata and N. × sanderae. Two unexpected acyl groups, 8-methyl nonanoate and decanoate were found in N. occidentalis subsp. hesperis. Longer chain groups were found in the petunia, tomato, and potato species studied.

T-phylloplanin proteins secreted to aerial surfaces of tobacco (Nicotiana tabacum) by short procumbent trichomes inhibit spore germination and blue mold disease caused by the oomycete pathogen Peronospora tabacina. Many other plants were found to contain water-washed leaf surface proteins (phylloplanins), but the functions and properties of these are not known. Here we extend earlier evidence for the antifungal activity of T-phylloplanins using a reverse genetics approach. RNA interference of the T-phylloplanin gene in tobacco 'T.I. 1068' resulted in loss of T-phylloplanin mRNA and protein, loss of in vitro spore germination inhibition activity, and leaf infection inhibition activity of leaf water washes from RNA interference plants, and young knockdown plants were susceptible to disease. The glycoprotein character, adaxial-leaf-surface enrichment of, and renewability of T-phylloplanins are also described. We also report that leaf water washes of sunflower (Helianthus annuus) and jimson weed (Datura metel), but not soybean (Glycine max), like that of tobacco, possess ProteinaseK-and boiling-sensitive P. tabacina spore germination and tobacco leaf infection inhibition activities. Results establish that T-phylloplaninins of tobacco are active in P. tabacina inhibition, and indicate that leaf surface proteins of certain non-Nicotiana species that are not susceptible to P. tabacina disease can inhibit germination of spores of this oomycete pathogen and inhibit tobacco leaf infection by this pathogen.