Pepper gene encoding a basic pathogenesis‐related 1 protein is pathogen and ethylene inducible

A new basic pathogenesis‐related (PR)‐1 cDNA (CABPR1) was isolated from a cDNA library of pepper leaves infected with Xanthomonas campestris pv. vesicatoria. The full‐length clone contains an open reading frame of 531 nucleotides encoding 177 amino acid residues with a predicted molecular mass of 20241 and pI of 8.1. The deduced amino acid sequence of CABPR1 has a high level of identity with PR‐1 proteins from tobacco and tomato. Expression of the CABPR1 mRNA was greatly induced in an incompatible interaction of pepper leaves with X. campestris pv. vesicatoria. Accumulation of the basic PR‐1 mRNA in the bacteria‐infected leaves was intrinsically associated with the induction of ethylene biosynthesis. Treatment with 1‐aminoethoxyvinylglycine, an inhibitor of ethylene biosynthesis, strongly suppressed the induction of PR‐1 mRNA expression in the bacteria‐infected leaves. These data suggest that ethylene may function as a strong signal elicitor in the activation of PR‐1 genes, eventually mediating the plant defence response. Phytophthora capsici infection also distinctly stimulated ethylene biosynthesis, together with accumulation of PR‐1 mRNA. Expression of the basic PR‐1 mRNA was also induced in the pepper leaves by treatment with dl‐β‐amino‐n‐butyric acid or salicylic acid, but not by wounding. Treatment with methyl jasmonate, in combination with salicylic acid, strongly induced the PR‐1 transcripts. The basic PR‐1 gene expression occurred in untreated roots, flowers and green fruit of pepper but not in leaf, stem or red fruit.