Two 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 transcriptionally activated in fungus-infected parsley leaves or elicitor-treated, cultured parsley cells are shown to encode a hydroxyproline-rich glycoprotein (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 induced rapidly upon elicitation and precedes that of the HRGP gene. In situ hybridization experiments demonstrate the presence of HRGP and peroxidase mRNAs in parsley tissue around fungal infection sites. Peroxidase mRNA accumulation is particularly sharply restricted to plant cells directly adjacent to fungal hyphae. These results provide further evidence for an important role of specific cell wall modifications in plant defense.