2 PATHOGEN-RESPONSIVE GENES IN PARSLEY ENCODE A TYROSINE-RICH HYDROXYPROLINE-RICH GLYCOPROTEIN (HRGP) AND AN ANIONIC PEROXIDASE

Two recently isolated cDNAs representing genes that are transcriptiona lly activated in fungus-infected parsley leaves or elicitor-treated, c ultured parsley cells are shown to encode a hydroxyproline-rich glyco- protein (HRGP) and an anionic peroxidase. The deduced HRGP protein is rich in tyrosine residues, a feature also found in other pathogen- and wound-induced plant HRGPs. Expression of the peroxidase gene(s) is in duced rapidly upon elicitation and precedes that of the HRGP gene. In situ hybridization experiments demonstrate the presence of HRGP and pe roxidase mRNAs in parsley tissue around fungal infection sites. Peroxi dase mRNA accumulation is particularly sharply restricted to plant cel ls directly adjacent to fungal hyphae. These results provide further e vidence for an important role of specific cell wall modifications in p lant defense.