A new cell wall located n-rich protein is strongly induced during the hypersensitive response in Glycine max L.

Soybean (Glycine max (L.) Merill, cv. Williams 82) plants and cell cultures respond to avirulent pathogens with a hypersensitive reaction. After inocu lation of soybean with Pseudomonas syringae pv. glycinea, carrying the avir ulence gene avrA, or zoospores from the fungus Phytophthora sojae Race 1, a resistance-gene-dependent cell death programme is activated. A new gene wa s identified by differential display of mRNAs that is specifically activate d during the early phase of incompatible pathogen-soybean interactions but does not respond to compatible pathogens. The gene is strongly induced with in 2 h after addition of P. sojae zoospores. A similar kinetic pattern was observed for P. syringae (avrA) inoculated soybean cell cultures. The gene encodes a deduced protein of 368 amino acids with a very high content of as paragine and was therefore termed N-rich protein (NRP). The protein is comp osed of two distinct domains, of which only the C-terminal domain has strik ing homology to proteins of unknown function from other plants. An antibody raised against the recombinant NRP recognizes a protein of 42 kDa. The pro tein is located in the cell wall as indicated by cell fractionation studies . Comparison of the genomic DNA-sequence with the cDNA, identified two intr ons within the open reading frame. The NRP-gene is not directly induced by salicylic acid or hydrogen peroxide, indicating a distinct and specific sig nal transduction pathway which is only activated during programmed cell dea th. The NRP-gene appears to be a new marker in soybean activated early in p lant disease resistance.