Very long chain fatty acids plants

The conversion of fatty acids into very long chain fatty acids is specifically inhibited by the thiocarbamate herbicides such as EPTC and triallate (Figure 2.19). These compounds are used pre-plant incorporated for the control of grass and some small seeded broad-leaved weeds in crops such as maize and small grain cereals. 

Millar A. A. and Kunst L. (1997) Very-long-chain fatty acid biosynthesis is controlled through the expression and specificity of the condensing enzyme. Plant J. 12, 121-131. 

The biosynthesis of hydrocarbons occurs by the microsomal elongation of straight chain, methyl-branched and unsaturated fatty acids to produce very long-chain fatty acyl-CoAs (Figure 11.1). The very long chain fatty acids are then reduced to aldehydes and converted to hydrocarbon by loss of the carboxyl carbon. The mechanism of hydrocarbon formation has been controversial. Kolattukudy and coworkers have reported that for a plant, an algae, a vertebrate and an insect, the aliphatic aldehyde is decarbonylated to the hydrocarbon and carbon monoxide, and that this process does not require cofactors (Cheesbrough and Kolattukudy, 1984 1988 Dennis and Kolattukudy, 1991,1992 Yoder et al., 1992). In contrast, the Blomquist laboratory has presented evidence that the aldehyde is converted to hydrocarbon and carbon dioxide in a process that... 

OXIDATION IN PEROXISOMES /FOxidation of fatty acids also occurs within peroxisomes. In animals peroxisomal /Foxidation appears to shorten very long-chain fatty acids. The resulting medium-chain fatty acids are further degraded within mitochondria. In many plant cells, /Foxidation occurs predominantly in peroxisomes. (Fatty acids are not an important source of energy in most plant tissues. Although some plant mitochondria contain /Foxidation enzymes, this pathway is not... 

Millar, A.A., Wrischer, M., and Kunst, L. Accumulation of very-long-chain fatty acids in membrane glycerolipids is associated with dramatic alterations in plant morphology. Plant Cell 10, 1889-1902, 1998. 

Gassagne, G Bessoule, J-J Schneider, F Lessire, R Sturbois, B Moreau, P Spinner, G. Modulation of the very-long-chain fatty acid (VLGFA) formation in leek. In Kader J-K, Mazliak P, editors. Plant Lipid Metabolism. Dordrecht Kluwer, 1995, 111-114. 

The components of plant cuticular waxes have been reviewed by Kolattukudy (1980). Major components include hydrocarbons, very-long-chain fatty acids, alcohols and monoesters. These and minor components are shown in Table 2.5. 

Elongation of fatty acids is important in two commercial oil seeds, rape and jojoba. Most varieties of rape accumulate large quantities of d5-13-docosenoic (erucic) acid in their seed triacylglycerols. This is formed by elongation of oleic acid and the reactions have been studied in rape and the closely related Crambe abyssinica (Appleby etaL, 1974). Elongation in jojoba (which accumulates lipid as wax esters) uses a system with oleoyl-CoA and malonyl-CoA as substrates. The enzymes involved have been studied in jojoba and other plants where very-long-chain fatty acids are synthesized (Pollard and Stumpf, 1980). 

Based on our initial assessment of the relatively broad acyl specificity of yeast LPAT, and our interest in modifying the very long-chain fatty acid (VLCFA) content of Brassicaceae seed oils (4), we expressed the SLCl-1 gene in the model oilseed Arabidopsis thaliana, and in a high erucic acid B. napus cultivar. It will be shown that the yeast SLCl-1 gene can be used to change the content and composition of plant seed oils, via increased seed LPAT activity. 

Taylor, D.C., Barton, D.L., Rioux, K.P., MacKenzie, S.L., Reed, D.W., Underhill, E.W., Pomeroy, M.K. and Weber, N. (1992a) Biosynthesis of acyl lipids containing very-long chain fatty acids in microspore-derived and zygotic embryos of Brassica napus L. cv Reston. Plant Physiol. 99, 1609-1618. 

Cassagne C, Lessire R 1979 Biosynthesis of the very long chain fatty acids in higher plants from exogenous substrates. In Appelqvist LA, Liljenberg C (eds) Advances in the biochemistry and physiology of plant lipids. Elsevier New York, 383-398... 

Roudier, F., Gissot, L., Beaudoin, F., Haslam, R., Michaelson, L., Marion, J., Molino, D., Lima, A., Bach, L., Morin, H., Telher, F., Palauqui, J.C., Bellec, Y, Renne, C., Miquel, M., Dacosta, M., Vignard, J., Rochat, C., Markham, J.E., Moreau, R, Napier, J. and Faure, J.D. (2010) Very-long-chain fatty acids are involved in polar auxin transport and developmental patterning in Arabidopsis. Plant Cell 22, 364—375. 

Intracellular transport of very long chain fatty acids in etiolated leek seedlings. Plant Physiol. Biochem. 26, 173-178. 

Moreau P., Lessire R. and Casagne C. (1984) - In vivo membrane transfer of very long chain fatty acids synthesized by etiolated leek seedlings in Structure Function and Metabolism of plant Lipids, Siegenthaler P.A. et Eichenberger W., eds, Elsevier, Amsterdam, p. 307-310. 

Cassagne C, Lessire R, Bessoule JJ, Moreau P, Creach A, Schneider F, Sturbois B. Biosynthesis of very long chain fatty acids in higher plants. Prog Lipid Res 1994 33 55-69. 

THIOCARBAMATE ACTION ON VERY LONG CHAIN FATTY ACID SYNTHESIS IN PLANTS... 

The natural waxes play an important role, not only in controlling the water balance of the higher plants, but also in the penetration of xenobiotics. Attempts to improve the drug penetration rely on the control of waxes production As elongases are key enzymes in the synthesis of the aliphatic components of natural waxes, modulating very-long-chain fatty acids (VLCFA) production will have repercussions on the rate of wax synthesis. 

In summary, thiocarbamates have been shown to specifically affect very long chain fatty acid (and wax/cutin/suberin) synthesis in a variety of plant tissues in vivo. This effect is most likely due to the formation of a more active metabolite (possibly a sulfoxide) and can be reversed by safening agents. It seems probable that effects on fatty acid elongation are important in the mechanism of action of thiocarbamates. 

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