Regulation and function of the pepper pectin methylesterase inhibitor (<i>CaPMEI1</i>) gene promoter in defense and ethylene and methyl jasmonate signaling in plants
Analysis of the promoters of defense-related genes is valuable for determining stress signaling and transcriptional activation during pathogen infection. Here, we have isolated and functionally characterized the promoter region of the pepper ( Capsicum annuum ) pectin methylesterase inhibitor 1 ( CaPMEI1 ) gene in transiently transformed tobacco plants and stably transformed Arabidopsis plants. Among four 5′ deletion constructs analyzed, the −958-bp CaPMEI1 promoter induced a high level of GUS reporter activity in tobacco leaf tissue, driven by pathogen infection as well as by ethylene and methyl jasmonate (MeJA) treatment. The 204-bp region from −958 bp to −754 bp of the CaPMEI1 promoter is responsible for the stress-responsive expression. In addition, the pepper transcription factor CARAV1 activated the CaPMEI1 promoter in tobacco leaves, whereas the transcription factor CAbZIP1 did not. In the transgenic Arabidopsis plants, the −958 bp CaPMEI1 promoter was functionally regulated by developmental cues, bacterial and oomycete pathogen infections, and treatment with ethylene and MeJA. Histochemical GUS staining analyses of Arabidopsis tissues revealed that the CaPMEI1 promoter was mainly activated in leaf veins in response to various biotic and abiotic stimuli. Together, these results suggest that CaPMEI1 promoter activation may be a critical molecular event for host defense response and ethylene- and MeJA-mediated CaPMEI1 gene expression.