In situ localization of chitinase mRNA and protein in compatible and incompatible interactions of pepper stems with Phytophthora capsici

The induction of chitinase (CAChi2) mRNA started as early as 6 h after inoculation and gradually increased in the incompatible interaction of pepper stems with Phytotophthora capsici. In the compatihle interaction, the induction of the chitinase transcripts was detected later than that in the incompatible interaction. The CAChi2 mRNA was usually localized in the vascular tissues and their expression was constricted in the phloem-related cells. These results showed that the spatial pattern of CAChi2 mRNA expression was similar in both compatible and incompatible interactions but the temporal patterns were different from each other. In addition, the early induction of CAChi2 mRNA was quite distinct in the incompatible interaction. Immunogold labelling data showed specific labelling of chitinase on the cell wall of the oomycete in both compatible and incompatible interactions at 24 h after inoculation. In particular, numerous gold particles were deposited on the cell wall of P. capsici with a predominant accumulation over areas showing signs of degradation in the incompatible interaction. Chitinase labelling was also detected in the intercellular space and the host cytoplasm. However, healthy pepper stem tissue was nearly free of labelling. (C) 2000 Academic Press.