THE PLANT CELL, Vol 1, Issue 9 889-899, Copyright © 1989 by American Society of Plant Biologists
Expression of Holo and Apo Forms of Spinach Acyl Carrier Protein-I in Leaves of Transgenic Tobacco Plants
M. A. Post-Beittenmiller, K. M. Schmid and J. B. Ohlrogge
Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan 48824-1312
Acyl carrier protein (ACP) is a chloroplast-localized cofactor of fatty
acid synthesis, desaturation, and acyl transfer. We have transformed
tobacco with a chimeric gene consisting of the tobacco
ribulose-1,5-bisphosphate carboxylase promoter and transit peptide and the
sequence encoding the mature spinach ACP-I. Spinach ACP-I was expressed in
the transformed plants at levels twofold to threefold higher than the
endogenous tobacco ACPs as determined by protein immunoblots and assays of
ACP in leaf extracts. In addition to these elevated levels of the holo
form, there were high levels of apoACP-I, a form lacking the
4[prime]-phosphopantetheine prosthetic group and not previously detected in
vivo. The mature forms of both apoACP-I and holoACP-I were located in the
chloroplasts, indicating that the transit peptide was cleaved and that
attachment of the prosthetic group was not required for uptake into the
plastid. There were also significant levels of spinach acyl-ACP-I,
demonstrating that spinach ACP-I participated in tobacco fatty acid
metabolism. Lipid analyses of the transformed plants indicated that the
increased ACP levels caused no significant alterations in leaf lipid
biosynthesis.
