Characterization of a stress-responsive ankyrin repeat-containing zinc finger protein of Capsicum annuum (CaKR1).

We isolated many genes induced from pepper cDNA microarray data following their infection with the soybean pustule pathogen Xanthomonas axonopodis pv. glycines 8ra. A full-length cDNA clone of the Capsicum annuum ankyrin-repeat domain zinc finger protein (CaKR1) was identified in a chili pepper using the expressed sequence tag (EST) database. The deduced amino acid sequence of CaKR1 showed a significant sequence similarity (46%) to the ankyrin-repeat protein in very diverse family of proteins of Arabidopsis. The gene was induced in response to various biotic and abiotic stresses in the pepper leaves, as well as by an incompatible pathogen, such as salicylic acid (SA) and ethephon. CaKR1 expression was highest in the root and flower, and its expression was induced by treatment with agents such as NaCl and methyl viologen, as well as by cold stresses. These results showed that CaKR1 fusion with soluble, modified green fluorescent protein (smGFP) was localized to the cytosol in Arabidopsis protoplasts, suggesting that CaKR1 might be involved in responses to both biotic and abiotic stresses in pepper plants.