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 CATHI ON1 cDNA, which codes for thionin, was isolated from the cDNA library of pe pper leaves infected with Xanthomonas campestris pv. vesicatoria. A compari son of the CATHION1 and other known thionin genes revealed that the eight c ysteine residues are at the same location. Modes of transcriptional regulat ion of CATHION1 were compared between the compatible and incompatible inter actions. Transcripts of the CATHION1 gene were more induced in the incompat ible than compatible interactions of pepper leaves with X. campestris pv. v esicatoria, but occurred in a contrary manner in the interactions with Phyt ophthora capsici. Transcripts of the CATHION1 gene were constitutively expr essed in healthy pepper stems, but considerably accumulated upon infection by Virulent and avirulent isolates of P. capsici. CATHION1 mRNA was strongl y induced by treatment with ethephon or methyl jasmonate (MeJA), but somewh at weakly by salicylic acid (SA) and benzothiadiazole. These results sugges t that induction of CATHION1 mRNA by both SA and MeJA/ethylene may be invol ved in the signal transduction pathway of pepper defense- or pathogenesis-r elated plant responses for thionin synthesis in pepper plants. (C) 2000 Aca demic Press.