Ferredoxin from sweet pepper (Capsicum annuum L.) intensifying harpinpss-mediated hypersensitive response shows an enhanced production of active oxygen species (AOS) |
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Authors: | Dayakar Badri Venkata Lin Hao-Jan Chen Cheng-Hsien Ger Mang-Jye Lee Bor- Heng Pai Chia-Hwei Chow David Huang Hsiang-En Hwang Shaw-Yhi Chung Mei-Chu Feng Teng-Yung |
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Institution: | (1) Institute of Botany, Academia Sinica, Taipei, 115 29, Taiwan;(2) Institute of Life Science, National Defense Medical Center, Taipei, Taiwan;(3) Department of Plant Pathology, National Taiwan University, Taipei, Taiwan |
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Abstract: | The hypersensitive response (HR) is a form of cell death associated with plant resistance to pathogen infection. Harpinpss, an elicitor from the bacterium Pseudomonas syringae pv. syringae, induces a HR in non-host plants. Previously, we reported an amphipathic protein from sweet pepper interfering with harpinpss-mediated HR. In this report, we isolated and characterized a cDNA clone encoded that amphipathic protein from sweet pepper. This protein is designated as PFLP (plant ferredoxin-like protein) by virtue of its high homology with plant ferredoxin protein containing an N-terminal signal peptide responsible for chloroplast targeting and a putative 2Fe-2S domain responsible for redox activity. Recombinant PFLP obtained from Escherichia coliwas able to significantly increase active oxygen species (AOS) generation when mixed with harpinpss in tobacco suspension cells. It also showed enhanced HR when co-infiltrated with harpinpss in tobacco leaves. We used a transgenic tobacco suspension cells system that constitutively expresses the Pflpgene driven by the CaMV 35S promoter to study the function of PFLP in enhancing harpinpss-mediated hypersensitive cell death in vivo. In response to harpinpss, suspension cells derived from Pflptransgenic tobacco showed a significant increase both in the generation of AOS and in cell death as compared to the wild type. AOS inhibitors diphenylene iodonium chloride (DPI) and lanthanum chlorate (LaCl3) were used to study the involvement of AOS in harpinpss-induced cell death. Our results demonstrate enhanced generation of AOS is necessary to cause enhanced hypersensitive cell death in Pflp transgenic tobacco cells and it is plasma membrane-bound NADPH-oxidase-dependent. Sub-cellular localization studies showed that PFLP is present in the cytoplasm and chloroplast of Pflp transgenic tobacco cells, but only in the chloroplast, not in the cytoplasm, of wild-type tobacco cells. It is possible that PFLP can change the redox state of the cell upon harpinpss inoculation to increase AOS generation and hypersensitive cell death. Overall, this study will provide a new insight in the functional properties of ferredoxin in hypersensitive cell death. |
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Keywords: | active oxygen species ferredoxin hypersensitive cell death PFLP |
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