High affinity recognition of a Phytophthora protein by Arabidopsis via an RGD motif.
The RGD tripeptide sequence, a cell adhesion motif present in several extracellular matrix proteins of mammalians, is involved in numerous plant processes. In plant-pathogen interactions, the RGD motif is believed to reduce plant defence responses by disrupting adhesions between the cell wall and plasma membrane. Photoaffinity cross-linking of [125I]-azido-RGD heptapeptide in the presence of purified plasma membrane vesicles of Arabidopsis thaliana led to label incorporation into a single protein with an apparent molecular mass of 80 kDa. Incorporation could be prevented by excess RGD peptides, but also by the IPI-O protein, an RGD-containing protein secreted by the oomycete plant pathogen Phytophthora infestans. Hydrophobic cluster analysis revealed that the RGD motif of IPI-O (positions 53-56) is readily accessible for interactions. Single amino acid mutations in the RGD motif in IPI-O (of Asp56 into Glu or Ala) resulted in the loss of protection of the 80-kDa protein from labelling. Thus, the interaction between the two proteins is mediated through RGD recognition and the 80-kDa RGD-binding protein has the characteristics of a receptor for IPI-O. The IPI-O protein also disrupted cell wall-plasma membrane adhesions in plasmolysed A. thaliana cells, whereas IPI-O proteins mutated in the RGD motif (D56A and D56E) did not.
Surfaces Cellulaires et Signalisation chez les Végétaux, UMR 5546 CNRS-Université Paul Sabatier, 31326 Castanet Tolosan cedex, France.
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Senchou
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Weide
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Carrasco
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Bouyssou
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Pont-Lezica
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Govers
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Canut
D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010838:Phytophthora / Q000378:metabolism*
D029681:Arabidopsis Proteins; D005656:Fungal Proteins; C112546:IpiO1 protein, Phytophthora infestans; D008565:Membrane Proteins; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid