Expression of the Yeast Δ-9 Fatty Acid Desaturase in Nicotiana tabacum

Abstract

To examine the processes of plant cytoplasmic fatty acid desaturation and glycerolipid biosynthesis, the protein coding sequence of the endoplasmic reticulum cytochrome b5-dependent, A-9 fatty acid desaturase gene from Saccharomyces cerevisiae was introduced into Nicotiana tabacum via Agrobacterium transformation. All transformed plants expressing the yeast gene at the mRNA level exhibited an approximately 10-fold increase in the levels of palmitoleic acid (16:1) in leaf tissue. This fatty acid species is found in very low levels (less than 2%) in wild-type plants. These results indicate that the yeast desaturase can function in plants, presumably by using a leaf microsomal cytochrome b5-mediated electron transport system. Lipid analysis demonstrated that the overproduced 16:1 is incorporated into most of the major polar lipid classes, including the cytoplasmically produced "eukaryotic" fraction of the chloroplast galactolipids. 16:1 was not found, however, in phosphatidyl glycerol, which is considered to be produced almost exclusively in the chloroplast. Despite these changes in membrane lipid composition, no obvious phenotypic differences were apparent in the transformed plants. Positional analysis shows that the cytoplasmically produced 16:1 is found primarily in the sn-2 position of phosphatidylcholine, phosphatidylethanolamine, monogalactosyldiacylglycerol, and digalactosyldiacylglycerol. The positional data suggest that the sn-2 acyltransferases responsible for the "eukaryotic" arrangement of 16-and 18-carbon fatty acids in glycerolipids are selective for unsaturated fatty acids rather than chain length.In plants, unsaturated fatty acids are formed and incorporated into complex lipids in two distinct cellular compartments. The initial products of de novo fatty acid synthesis, which occurs almost exclusively in the plastids (12), are the saturated species 16:0-ACP2 and 18:0-ACP. 18:1-ACP is

Identification of an animal ω-3 fatty acid desaturase by heterologous expression in Arabidopsis

“…Mutants deficient in each of the major desaturases are available in Arabidopsis (11). Genes that encode the 18:0-CoA desaturases from yeast and mammals have been expressed in plants and shown to alter the fatty acid compositions of the plant tissues (27,28). These considerations recommended Arabidopsis as a suitable heterologous system to study the expression and function of the fat-1 gene.…”

Expression of the Arabidopsis ADS1 gene in Brassica juncea results in a decreased level of total saturated fatty acids

“…In fact, both 24:0 and 24:1 (cis-15) were decreased in transgenic seeds in comparison with the controls (Tables 1 and 2). A corresponding increase in 20:1 (cis-11) was detected in the T 1 transgenic seeds (Table 1), a similar increase in 20:1, however, was not found in T 2 transgenic seeds (Table 2) (Polashock et al, 1992;Wang et al, 1998;Xing and Chin, 2000). Expression of the RDS gene caused decreased 18:3 in all tobacco tissues but increased 18:2 in some tissues and decreased in other tissues (Moon et al, 2000).…”

Biosynthesis of C18 polyunsaturated fatty acids in microsomal membrane preparations from the filamentous fungus Mucor circinelloides

“…The ∆9 desaturase exhibited with Nbs 2 . LPCAT has been demonstrated in mammalian tissues, characteristics similar to those of the animal [20] and yeast enand higher rates of activity have been reported in oil-seed tissues zymes [21] in being membrane bound and utilising 18:0-CoA [28]. Little characterisation of the fungal activity has been un-as substrate.…”

“…Whether culture condiPlant and animal desaturases have been studied extensively [1Ϫ4]. With the exception of yeast [6,21], however, little infor-tions or strain variations account for this discrepancy requires sion of a borage desaturase cDNA containing an N-terminal cytofurther study. ∆6 desaturase activity in the Mucor membranes chrome b 5 domain results in the accumulation of high levels of was demonstrated to utilise linoleate at the sn-2 position of ex-∆ 6 -desaturated fatty acids in transgenic tobacco, Proc.…”

“…In animals (and yeast) the ∆9 desaturase is membrane nent (usually oil extracted from Evening Primrose seeds) causes bound, the substrate is stearoyl-CoA, and the associated electron significant health benefits for a range of disorders [9,10]. Re-transport utilises cytochrome b 5 [20,21]. The plant ∆9 desatucently, we have identified and characterised a cDNA encoding rase, by contrast, is a soluble protein that utilises stearoyl-acyl the ∆6 desaturase of the higher plant borage [11].…”