Identification of pathogen-responsive regions in the promoter of a pepper lipid transfer protein gene (CALTPI) and the enhanced resistance of the CALTPI transgenic Arabidopsis against pathogen and environmental stresses

The 5' flanking region of the CALTPI gene, which encodes a basic lipid transfer protein, was isolated and characterized from the genomic DNA of Capsicum annuum. Four different regions of the promoter sequence of the CALTPI gene were fused to the b-glucuronidase (GUS) coding region. In an Agrobacterium-mediated transient expression assay, the transcriptional activations of the promoter deletions were examined in tobacco leaves after infection with Pseudomonas syringae pv. tabaci, and treatment with ethylene and salicylic acid. The -808 bp region of the CALTPI gene promoter sequence exhibited full promoter activity. The W-box and ERE-box elements, which are essential for induction by all signals, were localized in the region between -555 bp and -391 bp upstream of the translation initiation site. A CALTPI transgene was then introduced under the control of the 35S promoter into the Arabidopsis ecotype Col-0. Transgenic Arabidopsis lines expressing the CALTPI gene developed rapidly compared to the wild-type plants, indicating that CALTPI may be involved in plant development. Overexpression of the CALTPI gene enhanced the resistance against infection by P. syringae pv. tomato and Botrytis cinerea. The transgenic plants expressing the CALTPI gene also showed high levels of tolerance to NaCl and drought stresses at various vegetative growth stages. No transcription of the PR-1, PR-2, PR-5, thionin, and RD29A genes was observed in untreated leaf tissues of the transgenic plants. The enhanced resistance to pathogen and environmental stresses in transgenic Arabidopsis correlated with the enhanced expression of the CALTPI gene.