Pepper gene encoding a basic class II chitinase is inducible by pathogen and ethephon

A chitinase cDNA clone (designated CAChi2) was isolated from the cDNA library of pepper leaves infected with Xanthomonas campestris pv. vesicatoria. The 1004-bp full-length CAChi2 cDNA encodes a basic chitinase with an N-terminal 24 amino acid signal peptide followed by a catalytic region. An analysis of its sequence indicates that CAChi2 is a class II chitinase, because it does not have chitin-binding domain and C-terminal extension sequences. The deduced amino acid sequence of CAChi2 has a high level of identity with class II chitinases from potato, tomato, tobacco and petunia. Southern analysis demonstrated that the CAChi2 chitinase is encoded by a single or two copy genes in the pepper genome. Following X. campestris pv. vesicatoria or Phytophthora capsici infection, the CAChi2 chitinase mRNA was more highly expressed in the incompatible interaction, compared to expression in the compatible interaction. Treatment with ethylene-releasing ethephon resulted in a strong accumulation of the transcripts in the leaves. In contrast, DL-beta-amino-n-butyric acid, salicylic acid and methyl jasmonate were not effective in inducing CAChi2 transcripts in pepper leaves.