Bouwmeester, K.

Canut, H.

Gouget, A.

Govers, F.

Haget, N.

Klamer, S.

English

NARCIS 

Lectin receptor kinase 79, a putative target of the Phytophthora infestans effector IPI-O

Name not available

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1 
Lectin receptor kinase 79, a putative target  
of the Phytophthora infestans effector IPI-O 
Klaas Bouwmeester1, Sofieke Klamer1, Anne Gouget2, Nathalie Haget2, Hervé 
Canut2, and Francine Govers1 
1Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 
PD Wageningen, the Netherlands; 2Surfaces Cellulaires et Signalisation chez 
les Végétaux, Unité Mixte de Recherche 5546 Centre National de la Recherche 
Scientifique-Université Paul Sabatier, 31326 Castanet Tolosan, France 
Francine.Govers@wur.nl 
Protection of plants against pathogen attack is governed by a variety of 
defense strategies. The outcome of a plant-pathogen interaction is determined 
by the virulence characteristics of the pathogen and the defense barriers 
present in the host. Pathogens have the capacity to suppress host defense 
responses, resulting in a situation in which a pathogen can thrive and 
reproduce on host tissue (basal compatibility). During evolution plants 
acquired specific resistance (R) proteins that can recognize pathogen-specific 
factors, so-called effectors. This recognition leads to effector triggered 
immunity (ETI) and is often associated with a hypersensitive response (HR) 
that blocks further growth of the pathogen. Although the majority of the R 
proteins described to date are intracellular nucleotide-binding leucine-rich-
repeat (NBS-LRR) proteins (DeYoung and Innes, 2006), ETI can also be 
based on membrane associated receptors, such as Cf-like LRR proteins or 
receptor-like kinases (RLKs). Examples of the latter are rice Xa21 that 
confers resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae 
and the Arabidopsis ERECTA protein. ERECTA not only functions as 
signalling component in plant organ development but also in ETI to Ralstonia 
solanacearum (Godiard et al., 2003). Other well-known Arabidopsis RLKs 
that can activate plant defense pathways are FLS2 and EFR. These RLKs are 
receptors for the pathogen associated molecular patterns (PAMPs) flg22 and 
EF-Tu, respectively, and thus activate PAMP triggered immunity (PTI) 
(Gomez-Gomez and Boller, 2002; Zipfel et al., 2006). 
  
2  |  BIOLOGY OF PLANT-MICROBE INTERACTIONS, VOLUME 6
Pathogens produce numerous PAMPs and effectors that can trigger ETI or 
PTI, or can reprogram host cells in order to promote infection. Phytophthora 
species contain large families of highly divergent effectors sharing a 
conserved motif named RxLR-dEER. This motif is thought to play a role in 
translocating these effectors into host cells. How plant cells perceive RxLR-
dEER effectors is virtually unknown. 
The cell wall – plasma membrane continuum 
In plants as well as animals, the extracellular matrix (ECM) is the first line 
of exposure to invading pathogens. In animals contacts between the ECM and 
the intracellular actin cytoskeleton are established by integrins, a family of 
transmembrane receptors that play a role in many diffferent signalling 
pathways. Integrins are also chosen by pathogens as a target for binding and 
their role in animal innate immune responses has been emphazised in several 
reports (Isberg and Van Nhieu, 1994; Pribila et al., 2004). Extracellular 
domains of integrins can bind to a variety of ECM glycoproteins that possess 
a conserved RGD tripeptide motif. The fact that membrane to matrix 
interactions can be easily disrupted by adding synthetic RGD-peptides shows 
that RGD mediating interactions are important for the ECM-plasma 
membrane continuum  (Canut et al., 1998; Gronowicz and Derome, 1994). 
Also in plants RGD-peptides are capable to disrupt cell wall-plasma 
membrane adhesions but remarkably, extensive studies did not result in the 
identification of integrin homologs in plants. Canut et al. (1998) showed 
however, that Arabidopsis thaliana contains high affinity RGD-binding sites 
in the plasma membrane pointing towards functional homologs of integrins in 
plants. Surprisingly one of these binding sites had a very high affinity for IPI-
O, an RxLR-dEER effector from the potato late blight pathogen 
Phytophthora infestans. IPI-O has an RGD tripeptide motif that overlaps with 
the RxLR motif and since the affinity for IPI-O was lost when mutated into 
RGA or RGE, the RGD motif seems to be crucial for binding (Senchou et al., 
2004). To identify proteins that potentially interact with the RGD motif in 
IPI-O a phage display screen was performed resulting in two heptamers that 
could inhibit plasma membrane RGD-binding activity in Arabidopsis and 
disrupt cell wall-plasma membrane adhesions. Blasting the Arabidopsis 
proteome with these peptide sequences led to the identification of Lectin 
Receptor Kinase 79 (LecRK79) as a putative effector target of IPI-O (Gouget 
et al., 2006). 
 
  
BIOLOGY OF PLANT-MICROBE INTERACTIONS, VOLUME 6  |  3 
The role of lectin receptor kinase 79 in plant defense 
Lectin receptor kinases (LecRKs) are found to be wide-spread in higher 
plants. For example, Arabidopsis thaliana contains 43 LecRKs, divided over 
several classes. The extracellular domains of LecRKs have features of soluble 
legume lectins which are believed to be involved in the recognition of simple 
sugars. Sequence analysis showed however, that LecRKs lack an essential 
aspartic residue (Asp81) in their sugar-binding sites, whereas molecular 
modeling showed a good conservation of the overall structure of legume 
lectins. This suggests that LecRKs are unlikely to bind simple sugar 
molecules but are more likely to recognize complex glycans. To test the 
hypothesis that LecRK79 is the effector target of IPI-O we set out to address 
the role of LecRK79 in plant defense. 
As a first step we analysed expression of LecRK79 in Arabidopsis plants 
that were exposed to various biotic agents and abiotic stress factors using a 
GUS-reporter-aided approach. The promoter of the Arabidopsis LecRK79 
gene was fused to a GUS reporter gene and introduced into Arabidopsis Col-
0.  Homozygous PLecRK79::GUS transgenic lines were selected and used for 
histochemical staining to monitor GUS activity indicative for active 
expression of LecRK79. When growing the transgenic PLecRK79::GUS plants 
without applying stress, GUS activity was detected in the main veins of 
rosette leaves and cotyledons and in all hypocotyl cell layers. In roots GUS 
activity was observed in the apex and stele of apical roots, root primordia and 
in lateral and adventive roots. These observations point to a basal level of 
LecRK79 expression in several cell types. 
When the transgenic plants were subjected to heat- or cold treatments or 
exposed to high salinity no increase in GUS activity was found when 
compared to untreated control plants. Also treatment with the hormone 
salicylic acid resulted in a GUS staining profile comparable to that in water 
treated plants. However, treatment with methyl jasmonate showed a strong 
induction of GUS activity, suggesting that genes in the jasmonate signalling 
pathway are involved in activating LecRK79 expression. Since wounding of 
plant tissue induces jasmonate signalling, we also tested the effect of 
wounding on LecRK79 expression. Wounding did not reveal a visible change 
in LecRK79 expression suggesting that wounding does not activate or repress 
all pathways that are regulated by jasmonate. In summary, these experiments 
show that the Arabidopsis LecRK79 promoter is not highly responsive to 
abiotic stresses. 
To reveal changes in LecRK79 expression resulting from biotic stress the 
PLecRK79::GUS plants were inoculated with a variety of pathogens. Inoculation 
with the necrotrophic fungus Botrytis cinerea resulted in typical necrotic 
  
4  |  BIOLOGY OF PLANT-MICROBE INTERACTIONS, VOLUME 6
lesions and was associated with a fast and strong induction of LecRK79 
expression in inoculated leaves. Inoculations with biotrophic pathogens were 
performed with strains that are either compatible or incompatible with 
Arabidopsis Col-0. Interestingly, in all cases clear differences were observed 
between compatible and incompatible interactions (Table 1). For example, in 
leaves infiltrated with an avirulent strain of Pseudomonas syringae, DC3000-
avrRPM1, there was a strong induction of LecRK79 expression. In the 
compatible interaction, however, the GUS staining was similar to the water 
control. Analysis of LecRK79 expression by Q-RT-PCR showed comparable 
results. A similar response was observed when the plants were infected with 
Phytophthora brassicae. In an incompatible interaction with strain HH the 
expression was higher than in the compatible interaction with strain 
CBS686.95 (Fig.1). Moreover, expression of LecRK79 was induced in a non-
host interaction with P. infestans.  In summary, expression of LecRK79 is 
induced during interaction with a necrotrophic pathogen B. cinerea and in 
incompatible interactions with biotrophic pathogens. This expression pattern 
suggests that LecRK79 has a role in pathways leading to programmed cell 
death or HR.  
 
Table 1. Induction of LecRK79 expression in Arabidopsis during compatible and 
incompatible plant-pathogen interactions. 
 
pathogen typea strain compatibilityb 
LecRK79 
expressionc 
Botrytis cinerea N IMI169558 C + 
DC3000 C - 
AvrRPT2 I + 
Pseudomonas 
syringae 
pv. tomato 
B 
AvrRPM1 I + 
IPO-0 I + Phytophthora 
infestans 
B 
NL88069 I + 
CBS686.95 C - Phytophthora 
brassicae 
B 
HH I + 
ª N: necrotrophic; B: biotrophic 
b C: compatible interaction; I: incompatible interaction 
c +: LecRK79 expression is increased; - LecRK79 expression stays at the basal level. 
  
BIOLOGY OF PLANT-MICROBE INTERACTIONS, VOLUME 6  |  5 
Concluding remarks 
Cell-wall associated defense responses that are necessary to block invading 
pathogens are dependent on the functionality of the continuum between cell 
wall and plasma membrane. When adhesions between cell wall and plasma 
membrane are disrupted this continuum becomes unbalanced and effective 
defense is lost. Pathogens are able to reprogram host cells in order to promote 
infection. Destabilizing the cell wall-plasma membrane continuum could be 
an obvious step in this process. IPI-O is a pathogen effector that has the 
capacity to disrupt cell wall-plasma membrane adhesions, to interact with 
RGD-binding sites on the plasma membrane and to compete with RGD-
containing proteins for those binding sites. Moreover, IPI-O has an RxLR-
dEER motif that may function as a host cell targeting signal. The putative 
effector target of IPI-O, LecRK79 also plays an important role in mediating 
adhesions. The finding that expression of LecRK79 is specifically induced in 
incompatible interactions suggests that LecRK79 has a role in defense. 
Possibly it counteracts the activity of a pathogen effector by either repairing 
cell wall-plasma membrane adhesions disrupted by the effector, or by 
preventing the effector to disrupt these adhesions. In a compatible interaction 
the effector may choose LecRK79 as a target for binding, possibly via RGD 
or the overlapping RxLR motif, and the basal level of LecRK79 may be 
sufficient to help the effector to enter the plant cell.  
Acknowledgements 
This reseach is supported by grants from the Netherlands Ministry of 
Agriculture, Nature and Food Quality (LNV427), EU-BioExploit (Food-CT-
2005-513959) and the Netherlands-French bilateral exchange program Van 
Gogh (NWO-VGP 85-343). 
 
Fig. 1. Arabidopsis leaves were inoculated with Phytophthora brassicae. In an 
incompatible interaction with strain HH (A) a strong induction of expression was 
observed, while in a compatible interaction with strain CBS686.95 (B) no induction of 
expression was detected. 
  
6  |  BIOLOGY OF PLANT-MICROBE INTERACTIONS, VOLUME 6
Literature cited 
Canut, H., Carrasco, A., Galaud, J.P., Cassan, C., Bouyssou, H., Vita, N., Ferrara, P., 
and Pont-Lezica, R. 1998. High affinity RGD-binding sites at the plasma 
membrane of Arabidopsis thaliana links the cell wall. Plant J. 16:63-71. 
DeYoung, B.J., and Innes, R.W. 2006. Plant NBS-LRR proteins in pathogen sensing 
and host defense. Nat. Immunol. 7:1243-1249. 
Godiard, L., Sauviac, L., Torii, K.U., Grenon, O., Mangin, B., Grimsley, N.H., and 
Marco, Y. 2003. ERECTA, an LRR receptor-like kinase protein controlling 
development pleiotropically affects resistance to bacterial wilt. Plant J. 36:353-
365. 
Gomez-Gomez, L., and Boller, T. 2002. Flagellin perception: A paradigm for innate 
immunity. Trends Plant Sci. 7:251-256. 
Gouget, A., Senchou, V., Govers, F., Sanson, A., Barre, A., Rouge, P., Pont-Lezica, 
R., and Canut, H. 2006. Lectin receptor kinases participate in protein-protein 
interactions to mediate plasma membrane-cell wall adhesions in arabidopsis. Plant 
Physiol. 140:81-90. 
Gronowicz, G.A., and Derome, M.E. 1994. Synthetic peptide containing Arg-Gly-
Asp inhibits bone formation and resorption in a mineralizing organ culture system 
of fetal rat parietal bones. J. Bone Miner. Res. 9:193-201. 
Isberg, R.R., and Van Nhieu, G.T. 1994. Binding and internalization of 
microorganisms by integrin receptors. Trends Microbiol. 2:10-14. 
Pribila, J.T., Quale, A.C., Mueller, K.L., and Shimizu, Y. 2004. Integrins and T cell-
mediated immunity. Annual Review of Immunology 22:157-180. 
Senchou, V., Weide, R., Carrasco, A., Bouyssou, H., Pont-Lezica, R., Govers, F., 
and Canut, H. 2004. High affinity recognition of a Phytophthora protein by 
Arabidopsis via an RGD motif. Cell. Mol. Life Sci. 61:502-509. 
Zipfel, C., Kunze, G., Chinchilla, D., Caniard, A., Jones, J.D.G., Boller, T., and 
Felix, G. 2006. Perception of the Bacterial PAMP EF-Tu by the Receptor EFR 
Restricts Agrobacterium-Mediated Transformation. Cell 125:749-760. 
 


Lectin receptor kinase 79, a putative target of the Phytophthora infestans effector IPI-O

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