scholarly journals The Cf-4 receptor-like protein associates with the BAK1 receptor-like kinase to initiate receptor endocytosis and plant immunity

2015 ◽  
Author(s):  
Jelle Postma ◽  
Thomas W. H. Liebrand ◽  
Guozhi Bi ◽  
Alexandre Evrard ◽  
Ruby R. Bye ◽  
...  

The first layer of plant immunity is activated by cell surface receptor-like kinases (RLKs) and proteins (RLPs) that detect infectious pathogens. Constitutive interaction with the RLK SUPPRESSOR OF BIR1 (SOBIR1) contributes to RLP stability and kinase activity. As RLK activation requires transphosphorylation with a second associated RLK, it remains elusive how RLPs initiate downstream signaling. To address this, we investigated functioning of Cf RLPs that mediate immunity of tomato against Cladosporium fulvum. We employed live-cell imaging and co-immunoprecipitation in tomato and Nicotiana benthamiana to investigate the requirement of associated kinases for Cf activity and ligand-induced subcellular trafficking of Cf-4. Upon elicitation with the matching effector ligands Avr4 and Avr9, BRI1-ASSOCIATED KINASE 1 (BAK1) associates with Cf-4 and Cf-9. Furthermore, Cf-4 that interacts with SOBIR1 at the plasma membrane, is recruited to late endosomes after elicitation. Significantly, BAK1 is required for Avr4-triggered endocytosis, effector-triggered defenses in Cf-4 plants and resistance of tomato against C. fulvum. Our observations indicate that RLP-mediated immune signaling and endocytosis require ligand-induced recruitment of BAK1, reminiscent of BAK1 interaction and subcellular fate of the FLAGELLIN SENSING 2 RLK. This reveals that diverse classes of cell surface immune receptors share common requirements for signaling initiation and endocytosis.

Author(s):  
Bruno Pok Man Ngou ◽  
Hee-Kyung Ahn ◽  
Pingtao Ding ◽  
Jonathan DG Jones

The plant immune system involves cell-surface receptors that detect intercellular pathogen-derived molecules, and intracellular receptors that activate immunity upon detection of pathogen-secreted effectors that act inside the plant cell. Surface receptor-mediated immunity has been extensively studied but in authentic interactions between plants and microbial pathogens, its presence impedes study of intracellular receptor-mediated immunity alone. How these two immune pathways interact is poorly understood. Here, we reveal mutual potentiation between these two recognition-dependent defense pathways. Recognition by surface receptors activates multiple protein kinases and NADPH oxidases, whereas intracellular receptors primarily elevate abundance of these proteins. Reciprocally, the intracellular receptor-dependent hypersensitive cell death response is strongly enhanced by activation of surface receptors. Activation of either immune system alone is insufficient to provide effective resistance against Pseudomonas syringae. Thus, immune pathways activated by cell-surface and intracellular receptors mutually potentiate to activate strong defense that thwarts pathogens. By studying the activation of intracellular receptors in the absence of surface receptor-mediated immunity, we have dissected the relationship between the two distinct immune systems. These findings reshape our understanding of plant immunity and have broad implications for crop improvement.


2001 ◽  
Vol 120 (5) ◽  
pp. A18-A19
Author(s):  
B DIECKGRAEFE ◽  
C HOUCHEN ◽  
H ZHANG

1985 ◽  
Vol 248 (6) ◽  
pp. H907-H913 ◽  
Author(s):  
L. J. Heller ◽  
R. A. Olsson

This study was designed to characterize adenosine's negative chronotropic effect on ventricular pacemakers. The spontaneous beating rate of isolated, isovolumic rat ventricular preparations perfused with Krebs-Henseleit solution decreased as the adenosine concentration was increased [log M effective concentration 50% (EC50) = -5.22 +/- 0.17]. The lack of effect of propranolol or atropine on this adenosine response eliminates the involvement of endogenous neurotransmitters. Support for the involvement of an external cell surface receptor was provided by findings that theophylline and 8-(4-sulfophenyl)theophylline, an analogue thought to act solely at the cell surface, significantly increased the adenosine log M EC50 to -3.94 +/- 0.22 and -3.61 +/- 0.22, respectively. An increase in spontaneous beating rate induced by theophylline, but not by its analogue, was blocked by the addition of propranolol. The relative chronotropic potency of the adenosine analogues R-PIA, S-PIA, and NECA suggests that the cell surface receptors may be of the Ri type. The negative chronotropic effects of adenosine and its analogues occurred at concentrations that had no effect on the developed pressure of the paced preparation. Electrocardiographic evaluations indicate that at high agonist concentrations, there was an abrupt alteration in electrical properties of the preparation, which could be blocked by theophylline and its analogue.


1979 ◽  
Vol 254 (9) ◽  
pp. 3194-3200
Author(s):  
A. Kulczycki ◽  
B L Hempstead ◽  
S L Hofmann ◽  
E W Wood ◽  
C W Parker

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