Ferredoxin from sweet pepper (Capsicum annuum L.) intensifying harpin sub(pss)-mediated hypersensitive response shows an enhanced production of active oxygen species (AOS)

• Published in: Plant molecular biology 2003-04, Vol.51 (6), p.913-924
• Main Authors: Dayakar, B V, Lin, H, Chen, C, Ger, M, Lee, B H, Pai, C, Chow, D, Huang, H, Hwang, S, Chung, M, Feng, T
• Format: Article
• Language: English
• ISSN: 0167-4412

The hypersensitive response (HR) is a form of cell death associated with plant resistance to pathogen infection. Harpin sub(pss), 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 harpin sub(pss)-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 coli was able to significantly increase active oxygen species (AOS) generation when mixed with harpin sub(pss) in tobacco suspension cells. It also showed enhanced HR when co-infiltrated with harpin sub(pss) in tobacco leaves. We used a transgenic tobacco suspension cells system that constitutively expresses the Pflp gene driven by the CaMV 35S promoter to study the function of PFLP in enhancing harpin sub(pss)-mediated hypersensitive cell death in vivo. In response to harpin sub(pss), suspension cells derived from Pflp transgenic 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 (LaCl sub(3)) were used to study the involvement of AOS in harpin sub(pss)-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 harpin sub(pss) 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.