Expression of Antisense Acyl Carrier Protein-4 Reduces Lipid Content in Arabidopsis Leaf Tissue

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Abstract
Arabidopsis plants were transformed with acyl carrier protein (ACP)-4 in antisense conformation driven by the cauliflower mosaic virus 35S promoter. It was hypothesized that reduction of ACP4 in leaf tissue would result in a reduction in lipid biosynthesis and, in addition, affect fatty acid composition and leaf physiology. Several transgenic lines have been generated with reduced ACP4 protein in leaf tissue. Dramatic reductions in ACP4 resulted in a reduction of leaf lipid content (22%-60%) based on fresh leaf weight and a bleached appearance and reduced photosynthetic efficiency. In addition, a decrease in 16:3 as a percentage of the total fatty acid composition was noted. There were no changes in leaf lipid class distribution; however, there was a decrease in the relative amount of 16:3 in monogalactosyldiacylglycerol. These results suggest that ACP4 plays a major role in the biosynthesis of fatty acids for chloroplast membrane development. Alterations in the ACP isoform profile of Arabidopsis leaf also appear to alter the flow of fatty acids between the prokaryotic and eukaryotic pathways for assembly of galactolipids. However, it has not yet been determined if the changes in fatty acid composition are due to changes in the profile of ACP isoforms, or if they are actually a reaction to a reduction in fatty acid precursors.