Differential expression and in situ localization of a pepper defensin (CADEF1) gene in response to pathogen infection, abiotic elicitors and environmental stresses in Capsicum annuum

Pepper defensin (CADEF1) clone was isolated from cDNA library constructed from pepper leaves infected with avirulent strain Bv5-4a of Xanthomonas campestris pv. vesicatoria. Putative protein encoded by CADEF1 gene consists of 78 amino acids including eight conserved cysteine residues to form four structure-stabilizing, disulfide bridges. Transcription of the CADEF1 gene was earlier and more strongly induced by X. campestris pv. vesicatoria infection in the incompatible than in the compatible interaction. CADEF1 mRNA was constitutively expressed in stem, root and green fruit of pepper. Transcripts of CADEF1 gene drastically accumulated in pepper leaf tissues treated with salicylic acid (SA), methyl jasmonate (MeJA), abscisic acid (ABA), hydrogen peroxide (H2O2), benzothiadiazole (BTH) and D,L-beta-amino-n-butyric acid (BABA). In situ hybridization results revealed that CADEF1 mRNA was localized in the phloem areas of vascular bundles in leaf tissues treated with exogenous SA, MeJA and ABA. Strong accumulation of CADEF1 mRNA occurred in pepper leaves in response to wounding, high salinity and drought stress. These results suggest that bacterial pathogen infection, abiotic elicitors and some environmental stresses may play a significant role in signal transduction pathway for CADEF1 gene expression. (C) 2004 Elsevier Ireland Ltd. All rights reserved.