Promoter analysis of the pepper antimicrobial protein gene, CaAMP1, during bacterial infection and abiotic stress

Abstract

In a previous study, we isolated and functionally characterized a novel antimicrobial protein gene with a high level of antimicrobial activity, CaAMP1, from pepper leaves infected with Xanthomonas campestris pv. vesicatoria. In this study, a series of 5'-deletions in the region -1190 bp upstream of the transcriptional start site of the CaAMP1 gene were analyzed in tobacco to determine the activity of the CaAMP1 promoter fused to the beta-glucuronidase (GUS) reporter gene, using an Agrobacterium-mediated transient expression assay. The CaAMP1 gene and promoter were locally and systemically induced by microbial infection. Several biotic and abiotic stress-related cis-acting elements, including GT1 box, W box, MYB, RAV1, ERE, and LTRE, were localized in the upstream promoter region of the CaAMP1 gene. The -1190, -967 and -626 bp regions of the CaAMP1 promoter activated by Pseudomonas syringae pv. tabaci infection, were simultaneously activated by treatments with salicylic acid and methyl jasmonate. The -1190 bp CaAMP1 promoter was also activated by abscisic acid, NaCl, and low temperature. Expression of the pepper transcription factor, CARAV1, but not CAZFP1, contributed to the activation of the CaAMP1 promoter. Deletion analysis of the CaAMP1 promoter suggested that some novel cis-acting elements are necessary for the induction of CaAMP1 expression during pathogen exposure and that environmental stresses may reside in the genomic sequence upstream of the CaAMP1 gene between -626 bp and -425 bp.