Ja. Sandoval et al., N-ACYLPHOSPHATIDYLETHANOLAMINE IN DRY AND IMBIBING COTTONSEEDS - AMOUNTS, MOLECULAR-SPECIES, AND ENZYMATIC-SYNTHESIS, Plant physiology, 109(1), 1995, pp. 269-275
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 hirsu
tom 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 a
nd 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 in
creased such that the relative percentage of NAPE was similar in dry a
nd soaked seeds (2.3 mol% compared to 2.6 mol%, respectively). The maj
or molecular species of NAPE were identified in both dry and soaked se
eds by fast atom bombardment mass spectrometry and collisionally activ
ated dissociation tandem mass spectrometry as 16:0/1 8:2-PE(N-palmitoy
l), 16:0/1 8:2-PE(N-linoleoyl), and 18:2/18:2-PE(N-palmitoyl). The spe
cific activity of NAPE synthase in seed extracts increased with increa
sing 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, o
ur results indicate that NAPE is present in dry cottonseeds and synthe
sized during imbibition. The biosynthesis of NAPE provides a mechanism
for maintaining membrane integrity during seed rehydration and may in
dicate that NAPE plays a protective role in intracellular membranes of
plant tissues, as has been suggested for intracellular membranes of a
nimal tissues.