Overexpression of the glycolytic enzyme pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP) in developing transgenic tobacco seed results in alterations in the onset and extent of storage lipid deposition

Abstract

Microscopy and fatty acid analyses were used to characterize the storage lipids in transgenic Nicotiana tabacum L. (tobacco) ovules demonstrating constitutive expression of a gene encoding pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP) from the protist Giardia lamblia. Transmission electron microscopy demonstrated significant differences in the size and number of lipid droplets in endosperm and embryo proper cells, regardless of the presence of the transgene; confocal fluorescence microscopy confirmed constitutive differences in lipid droplets of the endosperm and embryo tissues at maturity. Microscopy of developing tissues, however, showed that lipid droplets were deposited up to 48 h sooner in the transgenic embryo proper while deposition of endosperm lipids was unchanged. Cell counts of sectioned tissues confirmed that transgenic embryo growth was enhanced. Fatty acid analyses showed that fatty acid methyl ester (FAME) concentrations of stearic (18:0), linoleic (18:2), and linolenic (18:3) fatty acids were significantly higher in the larger, transgenic embryos, while those of palmitic (16:0) and oleic (18:1) were lower, suggesting that overexpression of PFP is responsible for altering both growth and development of young ovules. At maturity, palmitic and stearic FAMEs were significantly lower, but no other morphological or biochemical differences between the control and transgenic seeds could be measured.Key words: triacylglycerols, Nicotiana tabacum, transgenic, embryo development, storage lipids.