In situ hybridization study of organ- and pathogen-dependent expression of a novel thionin gene in pepper (Capsicum annuum)

Abstract

In healthy, untreated pepper plants, transcripts of thionin (CATHION1) gene were induced in an organ-specific manner, as revealed by RNA blot analysis and in situ hybridization. The CATHION1 mRNAs were expressed in stems and flowers as well as roots, but not in leaves and fruits. In the stem and root tissues, the CATHION1 mRNA was present in endodermis and the phloem. In contrast, the transcripts were uniformly located in all the cells of flower tissues. Northern blot analysis and in situ hybridization were also performed to examine the temporal and spatial expression patterns of thionin (CATHION1) mRNA in leaf and fruit tissues of pepper (Capsicum annuum L.) infected by anthracnose pathogens Colletotrichum coccodes and C. gloeosporioides, respectively. Transcripts of the CATHION1 gene were more rapidly induced in pepper leaves at the 4- than at the 8-leaf stage by C. coccodes infection. Typical anthracnose symptoms were observed on green pepper fruits inoculated with C. gloeosporioides, but not on red pepper fruits. The transcript accumulation was more pronounced in green fruits than in red fruits upon C. gloeosporioides infection. The CATHION1 transcripts were detected in the phloem cells infected by anthracnose pathogens.