PLANT PHYSIOLOGY , Vol 109, Issue 1 269-275, Copyright © 1995 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
N-Acylphosphatidylethanolamine in Dry and Imbibing Cottonseeds (Amounts, Molecular Species, and Enzymatic Synthesis)
J. A. Sandoval, Z. H. Huang, D. C. Garrett, D. A. Gage and K. D. Chapman
Department of Biological Sciences, Division of Biochemistry and Molecular Biology, University of North Texas, Denton, Texas 76203-0218 (J.A.S., D.C.G., K.D.C.)
N-Acylphosphatidylethanolamine (NAPE), an unusual acylated derivative of
phosphatidylethanolamine (PE), was recently shown to be synthesized from PE
and free fatty acids in cotyledons of cotton (Gossypium hirsutum L.)
seedlings (K.D. Chapman, T.S. Moore [1993] Plant Physiol 102: 761-769).
Here we report that NAPE is present in dry seeds of cotton and increases
with time of imbibition from 2.31 nmol/seed in dry seeds to 4.26 nmol/seed
in 4-h-soaked seeds. Total phospholipid/seed also increased such that the
relative percentage of NAPE was similar in dry and soaked seeds (2.3 mol%
compared to 2.6 mol%, respectively). The major molecular species of NAPE
were identified in both dry and soaked seeds by fast atom bombardment mass
spectrometry and collisionally activated dissociation tandem mass
spectrometry as 16:0/18:2-PE(N-palmitoyl), 16:0/18:2-PE(N-linoleoyl), and
18:2/18:2-PE(N-palmitoyl). The specific activity of NAPE synthase in seed
extracts increased with increasing time of imbibition from 35 pmol h-1 mg-1
protein in dry seeds to 129 pmol h-1 mg-1 protein in 4-h-soaked seeds.
Collectively, our results indicate that NAPE is present in dry cottonseeds
and synthesized during imbibition. The biosynthesis of NAPE provides a
mechanism for maintaining membrane integrity during seed rehydration and
may indicate that NAPE plays a protective role in intracellular membranes
of plant tissues, as has been suggested for intracellular membranes of
animal tissues.
