Pepper gene encoding thionin is differentially induced by pathogens, ethylene and methyl jasmonate

Infection by pathogens or treatment with abiotic elicitors led to a strong expression of thionin gene in pepper (Capsicum annuum L.) leaves. The CATHION1 cDNA, which codes for thionin, was isolated from the cDNA library of pepper leaves infected with Xanthomonas campestris pv. vesicatoria. A comparison of the CATHION1 and other known thionin genes revealed that the eight cysteine residues are at the same location. Modes of transcriptional regulation of CATHION1 were compared between the compatible and incompatible interactions. Transcripts of the CATHION1 gene were more induced in the incompatible than compatible interactions of pepper leaves with X. campestris pv. vesicatoria, but occurred in a contrary manner in the interactions with Phytophthora capsici. Transcripts of the CATHION1 gene were constitutively expressed in healthy pepper stems, but considerably accumulated upon infection by Virulent and avirulent isolates of P. capsici. CATHION1 mRNA was strongly induced by treatment with ethephon or methyl jasmonate (MeJA), but somewhat weakly by salicylic acid (SA) and benzothiadiazole. These results suggest that induction of CATHION1 mRNA by both SA and MeJA/ethylene may be involved in the signal transduction pathway of pepper defense- or pathogenesis-related plant responses for thionin synthesis in pepper plants. (C) 2000 Academic Press.