Overexpression of acyl carrier protein-1 alters fatty acid composition of leaf tissue, in arabidopsis

Acyl carrier protein (ACP) is a small (9 kD) acidic protein that is an esse ntial cofactor in plant fatty acid biosynthesis. Most plants have several i soforms of ACP, some of which are expressed constitutively and others that appear to be more tissue specific. Although the critical role of ACP in fat ty acid biosynthesis has been established, the role of the diverse number o f isoforms has yet to be elucidated. We have generated transgenic Arabidops is plants that express high levels of ACP-1, a seed-predominant ACP isoform , in leaf tissue under control of the cauliflower mosaic virus 35S promoter . Western and northern analysis of these plants demonstrate 3- to 8-fold in creased expression of this isoform in leaf tissue, but no significant chang es in seed. Analysis of the fatty acid composition of leaf tissue revealed that overexpression of ACP-1 in leaf tissue alters fatty acid composition. Significant decreases in levels of 16:3 were noted along with increases in 18:3. These findings represent the first in vivo report that overexpression of an ACP isoform results in changes in fatty acid composition in plants.