N-Acylethanolamine Signaling in Tobacco is Mediated by a Membrane-Associated, High-Affinity Binding Protein Page: 1,781
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N-Acylethanolamine Signaling in Tobacco Is Mediated by
a Membrane-Associated, High-Affinity Binding Protein1
Swati Tripathy, Kathryn Kleppinger-Sparace, Richard A. Dixon, and Kent D. Chapman*
Department of Biological Sciences, University of North Texas, Denton, Texas 76203 (S.T., K.K.-S., K.D.C.);
and Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73402 (R.A.D.)
N-Acylethanolamines (NAEs) are fatty acid derivatives found as minor constituents of animal and plant tissues, and their
levels increase 10- to 50-fold in tobacco (Nicotiana tabacum) leaves treated with fungal elicitors. Infiltration of tobacco leaves
with submicromolar to micromolar concentrations of N-myristoylethanolamine (NAE 14:0) resulted in an increase in relative
phenylalanine ammonia-lyase (PAL) transcript abundance within 8 h after infiltration, and this PAL activation was reduced
after co-infiltration with cannabinoid receptor antagonists (AM 281 and SR 144528). A saturable, high-affinity specific
binding activity for [3H]NAE 14:0 was identified in suspension-cultured tobacco cells and in microsomes from tobacco leaves
(apparent Kd of 74 and 35 nM, respectively); cannabinoid receptor antagonists reduced or eliminated specific [3H]NAE 14:0
binding, consistent with the physiological response. N-Oleoylethanolamine activated PAL2 expression in leaves and
diminished [3H]NAE 14:0 binding in microsomes, whereas N-linoleoylethanolamine did not activate PAL2 expression in
leaves, and did not affect [3H]NAE 14:0 binding in microsomes. The nonionic detergent dodecylmaltoside solubilized
functional [3H]NAE 14:0-binding activity from tobacco microsomal membranes. The dodecylmaltoside-solubilized NAE-
binding activity retained similar, but not identical, binding properties to the NAE-binding protein(s) in intact tobacco
microsomes. Additionally, high-affinity saturable NAE-binding proteins were identified in microsomes isolated from
Arabidopsis and Medicago truncatula tissues, indicating the general prevalence of these binding proteins in plant membranes.
We propose that plants possess an NAE-signaling pathway with functional similarities to the "endocannabinoid" pathway
of animal systems and that this pathway, in part, participates in xylanase elicitor perception in tobacco.
N-acylethanolamines (NAEs) constitute a class of
lipid compounds naturally present in both animal
and plant membranes as constituents of the
membrane-bound phospholipid, N-acylphosphati
dylethanolamine (NAPE). NAPE is composed of a
third fatty acid moiety linked to the amino head
group of the commonly occurring membrane phos-
pholipid, phosphatidylethanolamine (Schmid et al.,
1990; Chapman and Moore, 1993). NAEs are released
from NAPE by phospholipase D-type hydrolases in
response to a variety of stimuli (Di Marzo et al., 1994;
Schmid et al., 1996; Chapman et al., 1998; Hansen et
al., 1998). During the past decade, transient NAE
release and accumulation has been attributed a vari-
ety of biological activities, including neurotransmis-
sion (Schmid et al., 1996; Di Marzo, 1998a, 1998b),
membrane protection (Hansen et al., 2000), immuno-
modulation in animals (Klein et al., 1998), and de-
fense signaling in plants (Tripathy et al., 1999; Chap-
In animals, anandamide (NAE 20:4) was the first
NAE type to be identified as an endogenous signal-
1 This work was supported by the Texas Higher Education
Coordinating Board (grant no. ARP 003594-028), by the U.S. De-
partment of Agriculture National Research Initiative (grant no.
99-35304-8002), and by the Samuel R Noble Foundation.
* Corresponding author; e-mail firstname.lastname@example.org; fax 940-
Article, publication date, and citation information can be found
ing ligand for cannabinoid (CB) receptors (Devane et
al., 1992), and the diverse physiological functions of
CBs are mediated in part through the CB receptors
CB1 (Matsuda et al., 1990) and CB2 (Munro et al.,
1993). These CB receptors are G-protein coupled and
mostly localized to the central nervous and immune
systems (Pertwee, 1997, 1999; Martin et al., 1999),
respectively. Identification of these receptors and
their endogenous ligands has led to the development
of several CB analogs (WIN 55, 212-2, AM 281, SR
144528, etc.) that interact more specifically and po-
tently with CB receptors (Reggio, 1999). Together, the
NAEs and their receptors have emerged as active
signaling components of an "endocannabinoid" sys-
tem affecting both neuronal and immune functions in
animal systems (Salzet et al., 2000) and have become
targets of potential therapeutic applications (De Pet-
rocellis et al., 2000; Straus, 2000).
In plants, NAPE-NAE metabolism is widespread
(Chapman and Moore, 1993) and appears to be in-
volved in several physiological processes (Chapman,
2000). For example, a phospholipase D-mediated ac-
cumulation of extracellular NAE 14:0 was triggered
in tobacco (Nicotiana tabacum) cell suspensions
(Chapman et al., 1998) and leaves (Tripathy et al.,
1999) within minutes after elicitor perception. Nano-
molar concentrations of NAE 14:0 activated Phe
ammonia-lyase (PAL) gene expression in both cell
suspensions and leaves of intact plants in a manner
similar to, but independent of, pathogen elicitor
treatment. In addition, exogenously supplied NAE
Plant Physiology, April 2003, Vol. 131, pp. 1781-1791, www.plantphysiol.org 2003 American Society of Plant Biologists
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Tripathy, Swati; Kleppinger-Sparace, Kathryn; Dixon, R. A. & Chapman, Kent D. N-Acylethanolamine Signaling in Tobacco is Mediated by a Membrane-Associated, High-Affinity Binding Protein, article, April 2003; [Rockville, Maryland]. (https://digital.library.unt.edu/ark:/67531/metadc277313/m1/1/: accessed July 17, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.