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Plant Physiol. (1998) 117: 643-650
Desensitization of the Perception System for Chitin Fragments in
Tomato Cells
Georg Felix*,
Karl Baureithel1, and
Thomas Boller
Friedrich Miescher-Institut, P.O. Box 2543, CH-4002 Basel,
Switzerland
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ABSTRACT |
Suspension-cultured tomato
(Lycopersicon esculentum) cells react to stimulation by
chitin fragments with a rapid, transient alkalinization of the growth
medium, but behave refractory to a second treatment with the same
stimulus (G. Felix, M. Regenass, T. Boller [1993] Plant J 4:
307-316). We analyzed this phenomenon and found that chitin fragments
caused desensitization in a time- and concentration-dependent manner.
Partially desensitized cells exhibited a clear shift toward lower
sensitivity of the perception system. The ability of chitin oligomers
to induce desensitization depended on the degree of polymerization
(DP), with DP5  DP4  DP3 DP2 > DP1. This correlates
with the ability of these oligomers to induce the alkalinization
response and to compete for the high-affinity binding site on tomato
cells and microsomal membranes, indicating that the alkalinization
response and the desensitization process are mediated by the same
receptor. The dose required for half-maximal desensitization was about
20 times lower than the dose required for half-maximal alkalinization;
desensitization could therefore be used as a highly sensitive bioassay
for chitin fragments and chitin-related stimuli such as
lipochitooligosaccharides (nodulation factors) from Rhizobium
leguminosarum. Desensitization was not associated with
increased inactivation of the stimulus or with a disappearance of
high-affinity binding sites from the cell surface, and thus appears to
be caused by an intermediate step in signal transduction.
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INTRODUCTION |
Plant cells have the ability to perceive a variety of microbial
substances (Boller, 1995 ). Perception of some of these substances, such
as elicitors, may initiate phytoalexin production and other responses
associated with defense (Darvill and Albersheim, 1984; Ebel and Cosio,
1994). Perception of other microbial factors may initiate responses
important for symbiosis, e.g. the initiation of nodule formation in
legume roots by rhizobial Nod factors (Dénarié et al.,
1992). Both types of chemoperception systems are highly sensitive and
selective, indicating that they are mediated by specific receptors
(Ebel and Cosio, 1994; Boller, 1995). Indeed, high-affinity binding
sites with all of the characteristics of receptors have been identified
and characterized for a number of microbial substances in various
plants (Boller, 1995; Côté et al., 1995).
In previous studies with suspension-cultured tomato (Lycopersicon
esculentum) cells, we have identified highly sensitive perception systems for glycopeptides with a fungal-specific N-linked
glycan of 9 to 12 mannosyl units (Basse et al., 1992), for chitin
fragments (Felix et al., 1993), for ergosterol (Granado et al., 1995),
and for fungal xylanase (Felix et al., 1993, 1994). These compounds belong to very different classes of chemical structures but are highly
typical for fungi and are not known to occur in plants. High-affinity
binding sites specific for the glycopeptides (Basse et al., 1993) and
for the chitin fragments (Baureithel et al., 1994) could be
demonstrated on tomato cells and membranes.
Chemoperception systems in microbes and animals are often desensitized
by the continuous presence of the stimulus, allowing an increase in the
dynamic range of the sensory system (Dusenbery, 1992). We have observed
a similar effect on some of the chemoperception systems in tomato
cells. For example, cells reacted with a transient alkalinization of
the growth medium when treated with chitin fragments but did not
respond when treated with a second dose of chitin fragments, although
they still reacted to xylanase (Felix et al., 1993) or ergosterol
(Granado et al., 1995). Reciprocally, when cells were treated with
ergosterol, they were refractory to further stimulation with ergosterol
but still responded to chitin fragments and xylanase (Granado et al.,
1995). These observations indicate that the different chemoperception
systems are desensitized in an independent manner. Desensitization can
therefore be used experimentally to distinguish different types
(qualities) of stimuli. For example, tomato cells react to Nod factors
(which contain a chitin oligomer as a backbone) with an alkalinization
response and become refractory to subsequent stimulation by chitin.
Cells pretreated with chitin fragments show no response to Nod factors,
indicating that Nod factors and chitin fragments have the same sensory
quality for the tomato cells (Staehelin et al.,
1994).
In an attempt to study the processes underlying desensitization, we
describe here the characteristics of the refractory behavior in tomato
cells treated with chitin fragments. We present data on the time and
dose dependence of desensitization, and show that this process is not
associated with inactivation of the chitin fragments or with
disappearance of the binding site for chitin fragments from the cells.
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MATERIALS AND METHODS |
Chitin Fragments and Nod Factors
Chintin fragments CH2, CH3, CH4, and CH5 were obtained from
Seikagaku (Tokyo, Japan). The purified Nod factor Nod Rlv-V(Ac;C18:1) from Rhizobium leguminosarum bv viciae, CH5
modified at the nonreducing end by an O-acetyl group and an
N-linked unsaturated fatty acid (18:1) (Spaink et al.,
1991), was kindly provided by H.P. Spaink (Leiden State University,
Leiden, The Netherlands).
Cell Culture and Alkalinization Response
The tomato (Lycopersicon esculentum) cell line Msk8
(Koornneef et al., 1987) was maintained as a suspension culture (Felix et al., 1991a) and used 4 to 10 d after subculture for
experiments. To measure alkalinization of the growth medium (the
alkalinization response), 2.5-mL aliquots of the suspension were placed
in open, 20-mL vials on a rotary shaker at 120 cycles
min 1. The pH in the medium was continuously
measured using a small, combined-glass electrode (Metrohm, Herisau,
Switzerland) and registered on a pen recorder. The
 pHmax, which occurred 3 to 5 min after application of chitin fragments, was derived from the recordings (Felix
et al., 1993). The maximal pH increase obtained after stimulation with
saturating doses of CH4 (>1 nM) varied little within one experiment using one batch of cells (± approximately 0.03 pH unit), but varied between 0.5 and 0.8 in different experiments using different
batches of cells.
To use desensitization as a bioassay for chitin-related stimuli,
aliquots of cell suspension were pretreated for 60 min with chitin
fragments or the compounds to be tested, and the alkalinization response (pHmax) to subsequent treatment with
10 nM CH4 was recorded.
Binding Assay for Chitin Fragments
Binding of chitin fragments to whole cells was studied with a
35S-labeled derivative of CH5 as described
previously (Baureithel et al., 1994). One-milliliter aliquots of cell
suspension containing approximately 0.3 g fresh weight of cells
were incubated with 100 nCi of
CH5-Gly-[35S]Met-Boc (specific activity
approximately 1000 Ci mmol1) and 1 or 10 nM CH5 for 20 min on ice. Cells were collected on a paper
filter and washed with fresh, ice-cold medium. Radioactivity bound to
the cells was measured by scintillation counting.
Reproducibility
Data shown in figures are from single experiments representative
of at least three independent repetitions.
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RESULTS |
Dependence of Desensitization on Dose and Time
Suspension-cultured tomato cells react to treatment with
subnanomolar concentrations of chitin fragments or ergosterol with rapid alkalinization of their extracellular medium (Felix et al., 1993;
Granado et al., 1995). Examples of the alkalinization response are
shown in Figure 1. In cell cultures
treated with doses of 0.03, 0.3, or 3 nM
N,N ,N",N"-tetraacetylchitotetraose
(CH4) or 3 nM ergosterol, the pH in the medium started to
increase after a short lag, reached a maximum after approximately 5 min, and then decreased rapidly. pHmax was
0.76 and 0.54 in cells treated with 3 nM CH4 and 3 nM ergosterol, respectively. After this transient alkalinization the pH did not reach a constant, stable value but slowly
oscillated below and above the baseline observed in untreated control
cells (values for later time points not shown). Increasing the
concentration of CH4 to 1 µM resulted in a pH profile
indistinguishable from that observed with 3 nM CH4 (data
not shown), indicating that the response of tomato cells was saturated
at concentrations  3 nM.
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| Figure 1.
Induction of extracellular alkalinization in
suspension-cultured tomato cells in response to two consecutive
stimuli. Solid lines, Extracellular pH in untreated cells (control) or
cells treated with CH4 or ergosterol at the concentrations indicated. Shaded circles and dotted lines, Extracellular pH after a second stimulation with 10 nM CH4 (shown in the inset). The pH of
the growth medium was 5.1 at the start of the experiment.
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At different times after the application of the first stimulus, cells
were treated with 10 nM CH4 as a second stimulus (Fig. 1).
Cells initially treated with 3 nM CH4 did not react to the second stimulus, confirming earlier findings in cells treated with an
initial dose of 10 nM CH4 (Felix et al., 1993). Cells treated with an initial dose of 0.3 or 0.03 nM CH4
exhibited an alkalinization response when stimulated a second time
(Fig. 1). However, pHmax was considerably
lower than in control cells that had not received a first stimulus or
that had been stimulated with 3 nM ergosterol (Fig. 1). In
these cultures, the pHmax after stimulation
with 10 nM CH4 remained at approximately 0.7 to 0.8 throughout the experiment.
The responsiveness of cells after a first stimulation was assayed for a
broader range of CH4 concentrations and over a prolonged period of time
(Fig. 2). While treatment with 1 pM CH4 did not cause a decrease in the
pHmax reached in response to the second stimulation with 10 nM CH4, a significant decrease in
response occurred in cells treated with 3 and 10 pM CH4. In
cells pretreated with doses of 30 to 300 pM, the
responsiveness was minimal after 30 to 60 min of treatment and then
slowly recovered, but did not reach the responsiveness of untreated
cultures within the 4 h of the experiment. Thus, desensitization
is a gradual process that depends on the duration of the pretreatment
as well as on the initial dose of the first stimulus (Figs. 1 and 2).
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| Figure 2.
Time dependence of desensitization induced by
different doses of CH4. pHmax elicited by 10 nM CH4 in cells pretreated for different times with the
concentrations of CH4 indicated.  , Control (no CH4);  , 1 pM;  , 3 pM;  , 10 pM;  , 30 pM;  , 100 pM; and  , 300 pM.
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To study the sensitivity of the perception system after a first
stimulation, the dose-response relationship for CH4-induced alkalinization was measured with untreated control cells and with cells
pretreated for 60 min with 0.03, 0.3, and 3 nM CH4 (Fig. 3). In control cells the
EC50 value was approximately 40 pM
CH4. In contrast, EC50 values were 2 nM and about 10 nM in cells pretreated with
0.03 and 0.3 nM CH4, respectively. Cells pretreated with 3 nM CH4 did not exhibit measurable alkalinization when
treated with CH4 up to concentrations of 1 µM (Fig. 3).
This decrease in the sensitivity of the cells was specific for the
response to chitin fragments, and no change in dose dependency for
ergosterol was observed after pretreatment with 3 nM CH4
(data not shown).
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| Figure 3.
Dose-response curves for induction of the
alkalinization response (pHmax) by CH4 in cells
pretreated for 60 min with different concentrations of CH4.  ,
Control (no CH4); , 0.03 nM; , 0.3 nM;
and , 3 nM.
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Desensitization as a Bioassay for Chitin Fragments
Desensitization of cells could be used as a sensitive bioassay for
chitin-related stimuli. The EC50 for
desensitization (i.e. the concentration that leads to 50% reduction of
the pHmax in response to the second
stimulation by 10 nM CH4) was determined for chitin
oligomers with a DP between 1 and 5. The EC50 of
CH4 and CH5 for desensitization was approximately 5 pM
(Fig. 4; data not shown for CH5). The
smaller chitin fragments, CH3, CH2, and CH1, were much less effective
inducers of desensitization, with EC50 values of
1 nM, 4 µM, and 20 µM,
respectively (Fig. 4). The relative effectiveness of chitin oligomers
in the desensitization assay was CH5 CH4 CH3 CH2 > CH1, reflecting their relative effectiveness at stimulating the
alkalinization response (Felix et al., 1993). However, the bioassay
involving desensitization was much more sensitive, since the
EC50 values for desensitization were about 20 times lower than the EC50 values for the
alkalinization response.
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| Figure 4.
Dose-response curves for induction of
desensitization by different chitin oligomers. Alkalinization
(pHmax) in response to 10 nM CH4 was
measured in cells pretreated with different amounts of chitin oligomers
for 60 min.  , CH4; , CH3; , CH2; and , CH1. Hatched lines
indicate concentrations of the prestimuli that reduce
pHmax in response to 10 nM CH4 by 50%
(EC50 values for desensitization).
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A similar difference in sensitivity of the two bioassays was also
observed with Nod factors from R. leguminosarum. As
described previously for other Nod factors (Staehelin et al., 1994),
Nod Rlv-V(Ac;C18:1), a Nod factor that contains a CH5 backbone (Spaink et al., 1991), was found to induce alkalinization and desensitization to subsequent stimulation with (underivatized) chitin fragments. Cells
reacted with measurable alkalinization to concentrations of this Nod
factor greater than 0.1 nM, and their response was half-maximal at approximately 3 nM (Fig.
5). In the desensitization bioassay, 60 pM Nod factor was sufficient to reduce the subsequent stimulation by CH4 by 50% (Fig. 5). As observed previously (Staehelin et al., 1994), the maximal pH increase reached with saturating concentrations was lower with the Nod factor than with CH4: 0.30 pH
units with >30 nM Nod Rlv-V compared with 0.55 pH units
with 10 nM CH4 (Fig. 5). On the other hand, Nod Rlv-V at
concentrations greater than 3 nM induced complete
desensitization (Fig. 5).
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| Figure 5.
Dose-response curves for induction of an
alkalinization response and for induction of desensitization by a
purified Nod factor of R. leguminosarum, Nod
Rlv-V(Ac;C18:1). , Alkalinization (pHmax) in response
to different concentrations of Nod factor.  , Effect of 60 min of
pretreatment with different concentrations of the Nod factor on
alkalinization (pHmax) induced by 10 nM CH4.
Hatched lines indicate the EC50 values.
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Inactivation of Chitin Fragments by Cell Suspensions
A simple explanation for the refractory behavior of
cells would be a strongly accelerated inactivation of the chitin
fragments in cells pretreated with the stimulus, e.g. by a chitinase
activity induced by the pretreatment. As observed previously, the
activity of chitin fragments added to tomato cell suspensions
disappeared rapidly (Felix et al., 1993) (Fig.
6). This was tested by adding 10 nM CH4 to suspensions and assaying samples at intervals for their capacity to induce alkalinization (in fresh aliquots of cells).
However, the rate of inactivation in cells pretreated with 1 nM CH4 for 60 min was indistinguishable from that in cells without pretreatment (Fig. 6). In both suspensions, activity
disappeared with first-order kinetics, leading to an apparent half-life
of approximately 25 min for CH4 (Fig. 6). The same rate of inactivation was observed when CH4 was incubated in the cell-free medium obtained from the two cultures by filtration (Fig. 6). Because no inactivation was observed after heat treatment of the medium (95°C for 5 min; data
not shown), the inactivation of CH4 is best ascribed to the presence of
an enzyme activity, most likely a chitinase activity, in the culture
medium. The data described above show that desensitization is not
associated with enhanced degradation or inactivation of the chitin
fragments in prestimulated cells.
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| Figure 6.
Inactivation of chitin fragments in cell
suspensions before and after desensitization. Inactivation was tested
in suspensions without pretreatment (, ) or 60 min after
pretreatment with 1 nM CH4 (, ). At time 0, CH4 (10 nM) was added to cell suspensions or the corresponding
culture medium freed of cells by filtration. Samples were taken at
intervals, and serial dilutions were assayed for the induction of the
alkalinization response. Equivalents of CH4 in the samples were
determined from a standard curve obtained with untreated CH4. , Cell
suspension without pretreatment; , cell-free medium of control
cells; , cell suspension pretreated with 1 nM CH4; ,
cell-free medium from pretreated cells.
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Binding of Chitin Fragments by Desensitized Cells
We have previously developed an assay to study the high-affinity
binding sites for chitin fragments on intact tomato cells (Baureithel
et al., 1994). Using the radioligand
CH5-Gly-[35S]Met-Boc in the presence of 10 nM unlabeled CH5, conditions that saturate the binding
sites present on intact cells to approximately 80%
(Kd 1.4 nM; Baureithel et al.,
1994), we measured binding sites present on the cell surface in the
course of desensitization (Fig. 7). We
observed no significant change in binding to cells after pretreatment
with 0.03 or 0.3 nM CH4 (Fig. 7), indicating that the
number of binding sites did not change during the desensitization process. Similarly, no change in binding could be observed during the
desensitization process when binding was studied under less-saturating conditions (with only 1 nM unlabeled CH5, approximately
30% saturation; data not shown). These results suggest that
desensitization is not caused by changes in the number or the affinity
of the binding sites present on the cells.
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| Figure 7.
Binding of chitin fragments to intact tomato
cells. Cell suspensions were treated with 0.03 nM () or
0.3 nM () CH4 at time 0 as indicated. , Control (no
CH4). At intervals, 1-mL samples were taken and assayed for binding of
the radioligand CH5-Gly-[35S]Met-Boc in the presence of
10 nM unlabeled CH5. The dotted line without symbols
indicates binding of radioligand in the presence of 10 µM
CH5 (nonspecific binding).
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DISCUSSION |
Extracellular alkalinization has been observed in cell cultures of
many different plant species treated with a variety of elicitor
preparations and wound-related stimuli. This decrease of
H+ in the culture medium has been found to
coincide with an increase in K+ in the medium and
a depolarization of the plasma membrane (Mathieu et al., 1991; Kuchitsu
et al., 1993; Nürnberger et al., 1994; Felix and Boller, 1995).
However, the cellular mechanisms regulating these ion fluxes are not
known, nor have the ion channels and/or ion pumps involved been
identified. In this study we made use of the alkalinization response as
an indicator of the plant's reaction, much like the change in membrane
potential in neurophysiology, to analyze perception of chitin fragments
by tomato cells. Treatment of these cells with chitin fragments or
related molecules such as Nod factors led to rapid adaptation or
desensitization of the perception system. Desensitization of chitin
perception does not affect the response to unrelated stimuli such as
ergosterol or xylanase; reciprocally, cells stimulated by these
unrelated stimuli show no desensitization of the perception for chitin
fragments (Felix et al., 1993; Granado et al., 1995) (Fig. 1).
The transient nature of alkalinization induced by chitin fragments is
probably connected to desensitization. In cells treated with saturating
doses of chitin fragments (e.g. 1 nM CH4)
pHmax was reached after approximately 3 to 4 min. Thereafter, the pH decreased, irrespective of chitin fragments
still present (or added as a second dose) and even though cells still
had the capacity to respond with further alkalinization when treated
with unrelated stimuli. Therefore, the decrease in pH that follows the
peak of alkalinization is probably caused by a readjustment mechanism that prevails as soon as the perception system becomes desensitized. Indeed, cells rapidly readjust the pH of the growth medium when alkalinization is mimicked by the addition of small amounts of base
(data not shown). Although response to chitin fragments lasts for only
a few minutes, desensitization persists for several hours, even in the
absence of the stimulus (Felix et al., 1993).
The alkalinization response elicited by ergosterol is also transient
(Fig. 1), indicating that desensitization takes place in a similar
manner. In contrast to chitin fragments and ergosterol, xylanase
elicits an alkalinization lasting for several hours (Felix et al.,
1993), and the refractory behavior toward further additions of xylanase
could reflect a continuous, saturated response rather than
desensitization. In tobacco, the elicitor activity of xylanase has been
attributed to the xylanase protein itself rather than to plant cell
wall fragments released by its enzyme activity (Sharon et al., 1993).
We have similar evidence for direct elicitor activity of xylanase in
tomato (M. Bürgin, G. Felix, and T. Boller, unpublished results).
The relative ability of chitin fragments of different lengths to induce
desensitization paralleled their ability to induce alkalinization and
their affinity for the chitin-binding site on intact cells and
microsomal membranes (Baureithel et al., 1994). Similarly, the relative
effectiveness of the Nod factors in all of these assays was between
that of CH4 and CH3 (Baureithel et al., 1994) (Fig. 5). These data
strongly indicate that induction of the alkalinization response and
desensitization proceed by binding to the same receptor.
Desensitization can be observed at approximately 20-fold lower
concentrations than induction of alkalinization. Measurable
alkalinization probably requires the coherent, synchronous response of
many cells. The response to low concentrations might be impeded by the
kinetics of diffusion, leading to a broad, nonmeasurable peak of
alkalinization, or faint alkalinization might be masked by
nonstimulated (or desensitized) cells that readjust the pH in the
medium. Desensitization, in contrast, appears to proceed in a
cumulative manner, and low concentrations of chitin fragments can
cause progressive desensitization (Fig. 2).
Desensitization of the chitin-perception system is not unique to the
tomato cells used in this study; it was also observed in a cell culture
of tobacco (data not shown). However, desensitization was not observed
in a cell culture derived from a wild species of tomato,
Lycopersicon peruvianum. In these cells, consecutive treatments with chitin fragments stimulated repeated alkalinization (data not shown), as was also observed for stimulation of these cells
with systemin (Felix and Boller, 1995). The transient character of
medium alkalinization appears to be caused by inactivation/degradation of the chitin fragments rather than desensitization. In rice cells, chitin fragments with a DP > 7 have been reported to stimulate a
more permanent alkalinization response (Kuchitsu et al., 1993). Apparently, no rapid desensitization comparable with the one described in this study takes place.
We tested two simple hypotheses to account for the phenomenon of
desensitization, but had to reject both of them. The first hypothesis
was that desensitization might be connected to an increased ability of
the cells to modify or inactivate the ligand, for example, by increased
degradation or uptake or by the production of a specific inhibitor of
binding. However, our data show that the rate of disappearance of
biologically active chitin fragments was the same in control cells as
in prestimulated, desensitized cells. In both cases chitin fragments
disappear with apparent first-order kinetics and a half-life of
approximately 25 min (Fig. 6). The same rate of inactivation was
observed in the corresponding culture medium freed of cells by
filtration. Inactivation is thus best explained by chitinase activity
that is released by the cells and acts at a substrate concentration far
below its Km.
The second hypothesis was that the receptor itself might be altered in
its affinity to the ligand, or that it might be inactivated or
internalized. However, our binding data show that neither the number
nor the affinity of the binding sites for chitin fragments were
noticeably altered in desensitized cells compared with control cells
(Fig. 7). We could not detect alterations in the medium or at the cell
surface that could explain the phenomenon of desensitization. Therefore, we propose that desensitization occurs at an intracellular step in the signal transduction pathway leading to induction of alkalinization. Assuming that the alkalinization response induced by
different stimuli is based on the regulation of common channels or
pumps, signaling must converge at a certain point beforehand, and,
because desensitization is specific to the stimulus, a step occurring
before this convergence must be the target of desensitization.
A known mechanism for rapid desensitization of perception systems in
animal cells involves ligand-induced phosphorylation of the receptor,
as exemplified in the well-studied case of adrenergic receptors
(Lefkowitz et al., 1993). Induction of alkalinization in tomato cells
is correlated with specific changes in protein phosphorylation and can
be inhibited by the protein kinase inhibitor K-252a (Felix et al.,
1991b, 1994). If phosphorylation at the receptor or a step farther
downstream in the signaling pathway is involved in desensitization,
then the relevant phosphorylations are expected to be added quickly,
within 5 min of stimulation, and to persist throughout the period in
which desensitization is observed.
In microbial organisms and animals, adaptation and desensitization are
common characteristics of signal perception. These processes are
important to detect changes in signal intensities and gradients of
stimulus concentrations, e.g. in bacterial chemotaxis (Armitage, 1992)
or in the orientation of insects toward odorous sources (Stengl et al.,
1992). In both cases, removal of the stimulus usually leads to a rapid
reversal of desensitization (Armitage, 1992; Stengl et al., 1992). We
can only speculate about the biological role of desensitization in
tomato cells. Plants, as nonmotile organisms, might not be confronted
with the rapid increases and decreases in stimulus concentration that
are characteristic of chemotaxis. Nevertheless, they might need
information about increases in stimulus concentration. Desensitization
might allow an increase in the dynamic range of chitin-fragment
perception (Dusenbery, 1992), as indicated by the shift in sensitivity
of the perception system after a first stimulation. Therefore, a cell
that has not been exposed to chitin fragments previously will be
maximally sensitive and react in a dynamic range between 0.01 and 1 nM. After a response to these small doses of stimulus,
however, it will react in a higher dynamic range between 0.5 and 50 nM.
In conclusion, the desensitization of the perception system for chitin
fragments occurs rapidly in a time- and concentration-dependent manner,
and appears to be based on intermediate steps in signaling rather than
on the interaction of the stimulus with its binding site (receptor) on
the cell surface. A deeper understanding of this phenomenon must await
characterization of the receptor involved and the identification of the
elements downstream in the signal chain.
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FOOTNOTES |
1
Present address: Vifor International AG,
Rechenstrasse 37, CH-9001 St. Gallen, Switzerland.
*
Corresponding author; e-mail felix{at}fmi.ch; fax
41-61-697-45-27.
Received December 19, 1997;
accepted March 17, 1998.
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ABBREVIATIONS |
Abbreviations:
Boc, 4-butoxycarbonyl.
CH5, CH4, CH3, CH2, and
CH1, chitin fragments with DP 5, 4, 3, 2, and 1, respectively (CH1 = Glc-NAc) .
pHmax, maximal increase in pH above
baseline.
DP, degree of polymerization.
EC50, dose to
induce a half-maximal pH increase.
Nod, nodulation.
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ACKNOWLEDGMENTS |
We thank M. Regenass for his excellent technical assistance, Dr.
H.P. Spaink (Leiden State University) for the gift of Nod factors, and
Drs. M. Collinge and T. Meindl for helpful comments on the manuscript.
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LITERATURE CITED |
Armitage JP
(1992)
Behavioral responses in bacteria.
Annu Rev Physiol
54:
683-714
[CrossRef][Medline]
Basse CW,
Bock K,
Boller T
(1992)
Elicitors and suppressors of the defense response in tomato cells: purification and characterization of glycopeptide elicitors and glycan suppressors generated by enzymatic cleavage of yeast invertase.
J Biol Chem
267:
10258-10265
[Abstract/Free Full Text]
Basse CW,
Fath A,
Boller T
(1993)
High affinity binding of glycopeptide elicitor to tomato cells and microsomal membranes and displacement by specific glycan suppressors.
J Biol Chem
268:
14724-14731
[Abstract/Free Full Text]
Baureithel K,
Felix G,
Boller T
(1994)
Specific, high affinity binding of chitin fragments to tomato cells and membranes: competitive inhibition of binding by derivatives of chitooligosaccharides and a Nod factor of Rhizobium.
J Biol Chem
269:
17931-17938
[Abstract/Free Full Text]
Boller T
(1995)
Chemoperception of microbial signals in plant cells.
Annu Rev Plant Physiol Plant Mol Biol
46:
189-214
[CrossRef][ISI]
Côté F,
Cheong J-J,
Alba R,
Hahn MG
(1995)
Characterization of binding proteins that recognize oligoglucoside elicitors of phytoalexin synthesis in soybean.
Physiol Plant
93:
401-410
[CrossRef]
Darvill AG,
Albersheim P
(1984)
Phytoalexins and their elicitors: a defense against microbial infection of plants.
Annu Rev Plant Physiol
35:
243-275
[CrossRef][ISI]
Dénarié J,
Debellé F,
Rosenberg C
(1992)
Signalling and host range variation in nodulation.
Annu Rev Microbiol
46:
494-531
Dusenbery DB (1992) Sensory Ecology: How Organisms Acquire and
Respond to Information. Freeman, New York
Ebel J,
Cosio EG
(1994)
Elicitors of plant defense responses.
Int Rev Cytol
148:
1-36
Felix G,
Boller T
(1995)
Systemin induces rapid ion fluxes and ethylene biosynthesis in Lycopersicon peruvianum cells.
Plant J
7:
381-389
Felix G,
Grosskopf DG,
Regenass M,
Basse CW,
Boller T
(1991a)
Elicitor-induced ethylene biosynthesis in tomato cells. Characterization and use as a bioassay for elicitor action.
Plant Physiol
97:
19-25
[Abstract/Free Full Text]
Felix G,
Grosskopf DG,
Regenass M,
Boller T
(1991b)
Rapid changes of protein phosphorylation are involved in transduction of the elicitor signal in plant cells.
Proc Natl Acad Sci USA
88:
8831-8834
[Abstract/Free Full Text]
Felix G,
Regenass M,
Boller T
(1993)
Specific perception of subnanomolar concentrations of chitin fragments by tomato cells: induction of extracellular alkalinization, changes in protein phosphorylation, and establishment of a refractory state.
Plant J
4:
307-316
[CrossRef]
Felix G,
Regenass M,
Spanu P,
Boller T
(1994)
The protein phosphatase inhibitor calyculin A mimics elicitor action in plant cells and induces rapid hyperphosphorylation of specific proteins as revealed by pulse-labeling with [33P]phosphate.
Proc Natl Acad Sci USA
91:
952-956
[Abstract/Free Full Text]
Granado J,
Felix G,
Boller T
(1995)
Perception of fungal sterols in plants: subnanomolar concentrations of ergosterol elicit extracellular alkalinization in tomato cells.
Plant Physiol
107:
486-490
Koornneef M,
Hanhart CJ,
Martinelli L
(1987)
A genetic analysis of cell culture traits in tomato.
Theor Appl Genet
74:
633-641
[CrossRef]
Kuchitsu K,
Kikuyama M,
Shibuya N
(1993)
NAcetylchitooligosaccharides, biotic elicitors for phytoalexin production, induce transient membrane depolarization in suspension-cultured rice cells.
Protoplasma
174:
79-81
[CrossRef]
Lefkowitz RJ,
Cotecchia S,
Kjelsberg MA,
Pitcher J,
Koch WJ,
Inglese J,
Caron MG
(1993)
Adrenergic receptors: recent insights into their mechanism of activation and desensitization.
Adv Second Messenger Phosphoprotein Res
28:
1-9
[Medline]
Mathieu Y,
Kurkdjian A,
Xia H,
Guern J,
Koller A,
Spiro MD,
O' Neill M,
Albersheim P,
Darvill A
(1991)
Membrane responses induced by oligogalacturonides in suspension-cultured tobacco cells.
Plant J
1:
333-343
Nürnberger T,
Jabs D,
Nennstiel D,
Sacks WR,
Hahlbrock K,
Scheel D
(1994)
Specific recognition of a fungal oligopeptide elicitor by parsley cells.
Cell
78:
449-460
[CrossRef][ISI][Medline]
Sharon A,
Fuchs Y,
Anderson JD
(1993)
The elicitation of ethylene biosynthesis by a Trichoderma xylanase is not related to the cell wall degradation activity of the enzyme.
Plant Physiol
102:
1325-1329
[Abstract]
Spaink HP,
Sheeley DM,
Van Brussel AAN,
Glushka J,
York WS,
Tak T,
Geiger O,
Kennedy EP,
Reinhold VN,
Lugtenberg BJJ
(1991)
A novel highly unsaturated fatty acid moiety of lipo-oligosaccharide signals determines host specificity of Rhizobium.
Nature
354:
125-130
[CrossRef][Medline]
Staehelin C,
Granado J,
Müller J,
Wiemken A,
Mellor RB,
Felix G,
Regenass M,
Broughton WJ,
Boller T
(1994)
Perception of Rhizobium nodulation factors by tomato cells and inactivation by root chitinases.
Proc Natl Acad Sci USA
91:
2196-2200
[Abstract/Free Full Text]
Stengl M,
Hatt H,
Breer H
(1992)
Peripheral processes in insect olfaction.
Annu Rev Physiol
54:
665-681
[CrossRef][ISI][Medline]
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Abstract
Introduction