고추의 전신획득저항성 발현에서 기주세포 요인과 고추 SAR8.2 및 bZIP transcription factor의 기능

다국어 초록 (Multilingual Abstract)

Plants infected by pathogens undergo reprogramming during initiation of both local defense and systemic acquired resistance (SAR), accompanied by the molecular and biochemical events, including expression of defense-related genes, oxidative burst and structural barriers. The inoculation of primary pepper leaves with the avirulent strain Bv5-4a strain of X. campestris pv. vesicatoria induced SAR in the non-inoculated, secondary leaves. Some defense-related genes were significantly induced in the uninoculated (secondary) leaf tissues after local infection with the avirulent pathogen. The conspicuous systemic accumulation of H2O2 and the strong increase in peroxidase activity in the pepper leaves occurred during the cell death process of the systemic micro-hypersensitive responses (HR), leading to the induction of SAR. The SAR8.2 genes CASAR82A, CASAR82B and CASAR82C were isolated from pepper leaves infected with X. campestris pv. vesicatoria. The bZIP transcription factor, CAbZIP1 protein, that physically interacted with the CASAR82A protein also was isolated using the yeast two-hybrid system. The CASAR82A and CAbZIP1 were locally or systemically induced in pepper plants by X. campestris pv. vesicatoria infection. The pathogen-inducible genes also were differentially induced in pepper leaves by treatments with abscisic acid, ethylene, methyl jasmonate, salicylic acid, high salinity, drought and low temperature. The CASAR82A-GFP proteins were targeted in the intercellular space, whereas CAbZIP1-GFP proteins were localized in the nucleus. To better understand the mechanism, by which expression of the CASAR82A gene are regulated, the 5’ flanking region of the CASAR82A gene encoding SAR8.2 protein was isolated from the genomic DNA of pepper. The 831 bp sequence upstream of the CASAR82A gene was sufficient for full promoter activity in response to pathogen infection, abiotic elicitors and environmental stresses. For functional analysis of the CASAR82A gene, the CASAR82A transgene under control of 35S promoter was transformed into Arabidopsis ecotype Col-0. Ectopic expression of the CASAR82A gene in transgenic Arabidopsis plants conferred enhanced resistance to P. syringae pv. tomato DC3000, Botrytis cinerea and Fusarium oxysporum infection. he purified recombinant CASAR82A protein showed antimicrobial activity to broad range of phytopathogenic fungi. The CASAR82A-overexpressing plants also displayed enhanced tolerance to drought and high salt stresses at all the growth stages, but not to low temperature. The N-terminal region of CAbZIP1 fused to the GAL4 DNA-binding domain was required to activate transcription of reporter genes in yeast. Ectopic expression of CAbZIP1 in Arabidopsis exhibited dramatic alterations of plant morphology. The overexpression of the CAbZIP1 gene in transgenic Arabidopsis confers bacterial disease resistance and osmotic stresses tolerance.