An osmotin-like protein gene, CAOSM1, from pepper:: differential expression and in situ localization of its mRNA during pathogen infection and abiotic stress

An osmotin-like protein (CAOSM1) gene was isolated from pepper leaves infected with the avirutent strain Bv5-4a of Xanthomonas campestris pv. vesicatoria. The cDNA encoded a polypeptide of 250 amino acids with a molecular mass of 27,361 Da. Its amino acid sequence was highly homologous to various osmotin-like proteins from other plant species. The CAOSM1 gene expression was organ- and tissue-specifically regulated in pepper plants. The CAOSM1 mRNA was intensely localized in the endodermis area of root tissue and in the phloem cells of vascular bundles of red fruit tissue, but not in leaf, stem, and green fruit tissues of the healthy pepper plants. Infection by X. c. pv. vesicatoria, Collelotrichum coccodes, or Phytophthora capsici induced CAOSM1 transcription in the leaf and stem tissues. Expression of the CAOSM1 gene was somewhat higher and earlier in the incompatible than the compatible interactions in pepper leaves infected by pathogens. The CAOSM1 mRNA was prevalently localized in the phloem cells of the vascular bundle of leaf tissues infected by C. coccodes. The CAOSM1 gene was activated in leaf tissues by treatment with ethylene, inethyl jasmonate, high salinity, cold acclimation and mechanical wounding, but not by abscisic acid (ABA) and drought. These results indicate that the pepper CAOSM1 protein might play a role in the response to certain pathogens. (C) 2004 Elsevier Ltd. All rights reserved.