Accumulation of Pgip, a Leucine-Rich Receptor-Like Protein, Correlates with the Hypersensitive Response in Race-Cultivar Interactions

Abstract

The interaction between fungal endopolygalacturonases and a plant cell wall PGIP (polygalacturonase-inhibiting protein) in plant-pathogen recognition was shown to favour formation of oligogalacturonides able to elicit plant defence responses. Accumulation of pgip mRNA was studied in some race-cultivar interactions (compatible or incompatible) between Colletotrichum lindemuthianum and Phaseolus vulgaris by means of northern blot and in situ hybridization analyses. Rapid accumulation of pgip mRNA was correlated with appearance of the hypersensitive response in incompatible interactions, while a more delayed increase, coincident with the onset of lesion formation, occurred in compatible interactions. PGIP has a modular structure: its amino acid sequence can be divided into a set of 10.5 leucine-rich tandemly repeated units, each derived by modifications of a 24-amino acid peptide. A similar modular structure was observed in several proteins implicated in protein-protein interactions and in the extracellular domain of a cloned Arabidopsis leucine-rich receptor-like protein kinase (RLK5). A plasma membrane associated high molecular weight protein cross-reacting with an antibody prepared against PGIP is being purified.