Research interests MOLECULAR UNDERSTANDING OF PLANT-PATHOGEN INTERACTION
The plant cell death induced by an incompatible pathogen or by a pathogen released elicitor is recognized as a rapid, localized tissue collapse, termed hypersensitive response (HR). It has been known that HR is one of the most common events for a disease resistant host or non-host plant challenged by a pathogen. To reveal the molecular mechanism of HR may help us to understand how plants can be immune to pathogens. The long-term goal of our team is to explore the molecular mechanism of pathogen-mediated plant HR. We have identified and characterized two plant proteins, PFLP (Plant ferredoxin-like protein) and HRAP (HR assisting protein) in healthy plant leaves, which can interfere the activation of the HR caused by harpin (a proteineous elicitor secreted from bacterial pathogen) or a bacterial pathogen Pseudomonas syringae pv. syringae. Biological roles of PFLP and HRAP in HR have being studied in tobacco, tomato, broccoli, orchid and Arabidopsis plants.
1.
PFLP (Plant Ferredoxin-Like Protein)
PFLP is a ferredoxin (Fd)-like protein isolated from sweet pepper. It is a soluble protein with low molecular mass (11 kDa) and involving in the metabolism of photosynthesis, nitrate reduction, lipid synthesis and carbon synthesis. We are currently analyzing the role of PFLP play in the plant defense mechanism. In our study, it was demonstrated that plant endogenous amount of Fd was varied when host plant inoculated with different pathogen (figure 1). Incompatible pathogen Pseudomonas syringae pv. syringae (Pss) induces accumulation of Fd in host plant. However, the compatible pathogen Erwinia carotovora subsp. carotovora (Ecc) could reduce Fd amount in host plant. On the other hand, increasing amount of Fd by over expressing pflp gene in transgenic plant cause plant tolerant to inoculation of bacterial pathogen Pss and Ecc. This PFLP-mediated resistance raised by over expressing pflp gene in transgenic plant was due to induce active oxygen species (AOS) and hypersensitive cell death (HCD) in host plant. According to these findings, over-expressing pflp gene transgenic plants were obtained. We had obtained disease resistance plants, including transgenic rice against bacterial leaf blight, transgenic broccoli against bacterial soft rot, transgenic tomato against bacterial wilt and soft rot (Fig. 2) and transgenic calla lily against bacterial soft rot (Fig. 3). And this new finding will provide a new strategy for selecting disease resistance cultivars of different crops. In order to straighten out the predicaments of banana productivity in Africa, Academia Sinica was contracted with Africa Agriculture Technology Foundation (AATF) of the gene at August 11, 2006. And the gene was humanity authorized to control the wilt disease and improve the productivity of banana.
Fig. 1 The quantity of Fd-I was increased after the bacterial suspension of Pss (incompatible pathogen) was infiltrated into tobacco leaves (A), but Fd-I was decreased after the bacterial suspensions of Ecc (compatible pathogen) was infiltrated into tobacco leaves (B). The total protein of the infiltrated area was extracted and analysed by Western blotting with antiserum against PFLP. Leaves treated with phosphate buffer are indicated as Mock.
Fig. 2 The ferredoxin transgenic tomato line (24-18-7) showed more resistance against bacterial soft rot (A) and bacterial wilt (B) pathogens than wild type plant (Cln1558a).
Fig. 3 The 8 week old (a) and 4 week old (b) ferredoxin transgenic calla lily lines (Fa7 and Fa24) showed more resistance against bacterial soft rot pathogen than wild type plant.
2.
HRAP (Hypersensitive Response Assisting Protein)
The HRAP is a cationic hypersensitive response-assisting protein from sweet pepper, and this protein was found to be able to intensify the harpinPss-mediated HR in harpinPss-insensitive plants. However, it has no appreciable similarity to any known sequences. Sequence comparisons of HRAP showed it to contain a typical signal peptide leading to secretion into extracellular matrices. HRAP could dissociate harpinPss multimeric forms into dimeric and monomeric forms that could trigger a stronger HR necrosis in sweet pepper. We also found the expression of hrap gene was only induced by inoculation of non-compatible pathogens in sweet pepper. Constitutive expression of hrap gene in transgenic tobacco plant could enhance resistance against virulent bacterial pathogens, including Pseudomonas sp., Xanthomonas sp., and Erwinia sp. The applications of hrap gene need to be explored in our further study.
Hsiang-En Huang, Chien-An Liu, Mei-Jiuan Lee, C-George Kuo, Huei-Mei Chen, Mang-Jye Ger, Yu-Chih Tsai, Yen-Ru Chen, Ming-Kun Lin, and T-Y Feng 2007. Resistance enhancement of transgenic tomato to bacterial pathogens by the heterologous expression of sweet pepper ferredoxin-I protein (PFLP). Phytopathology 97:900-906.
Yip MK,Huang HE,Ger MJ, Chen CY, Chiu SH, Tsai YC, Lin CI and TY. Feng. 2007. Production of soft rot resistant cally lily by expressing a ferredoxin-like protein gene (pflp) in transgenic plants. Plant Cell Report 26:449-457.
Huang HE,Ger MJ, Chen CY, Pandey AK, Yip MK, Chou HW and TY. Feng. 2007. Dosease resisitance to bacterial pathogen effected by the qunatity of ferredoxin-I protein in plants. Molecular Plant pathology 8:129-137.
Tang, K.X., Sun, X.F., Hu, Q.N., Wu, A.Z., Lin, C.H., Lin, H.-J., Twyman, R.M., Christou, P., and Feng, T.-Y.(2001).
Trangenic rice plants expressing the ferredoxin-like proein (AP1) from sweet pepper show enhanced resistance to Xanthomonas oryzae pv. oryzae. Plant Sci. 160, 1035-1042.
Podile, A.R., Lin, H.J., Stainforth, V., Sripriya, P., Chen, L.-F.O., and Feng, T.-Y.(2001).
Conditional expression of harpinpss causes yeast cell death that shares features of cell death pathway with harpinpss-mediated hypersensitive response (HR). Physiol. Mol. Plant Pathol. 58, 267-276.
Dayakar, B.V., Lin, H.-J., Chen, C.-H., Ger, M.-J., Lee, B.-H., Pai, C.-H., Chow, D., Huang, H.-E., Hwang, S.-Y., Chung, M.-C., and Feng, T.-Y.(2003).
Ferredoxin from sweet pepper (Capsicum annuum L.) intensifying harpinpss-mediated hypersensitive response shows an enhanced production of active oxygen species (AOS). Plant Mol. Biol. 51, 913-924.
Ger, M.-J., Chen, C.-H., Hwang, S.-Y., Huang, H.-E., Podile, A.R., Dayakar, B.V., and Feng, T.-Y.(2003).
Constitutive expression of hrap gene in transgenic tobacco plant enhances resistance against virulent bacterial pathogens by induction of a hypersensitive response. Mol. Plant-Microbe Interact. 15, 764-773.
Liau, C.-H., Lu, J.-C., Prasad, V., Hsiao, H.-H., You, S.-J., Lee, J.-T., Yang, N.-S., Huang, H.-E., Feng, T.-Y., Chen, W.-H., and Chan, M.-T.(2003).
The sweet pepper ferredoxin-like protein (pflp) conferred resistance against soft rot disease in Oncidium orchid. Transgenic Res. 12, 329-336
You, S.-J., Liau, C.-H., Huang, H.-E., Feng, T.-Y., Prasad, V., Hsiao, H.-H., Lu, J.-C., and Chan, M.-T.(2003).
Sweet pepper ferredoxin-like protein (pflp) gene as a novel selection marker for orchid transformation. Planta 217, 60-65.
Huang, H.-E., Ger, M.-J., Yip, M.-K., Chen, C.-Y., Pandeya, A.-K., and Feng, T.-Y.(2004).
A hypersensitive response was induced by virulent bacteria in transgenic tobacco plants overexpressing a plant ferredoxin-like protein (PFLP). Physiol. Mol. Plant Pathol. 64, 103-110.
Pandey, A.-K., Ger, M.-J., Huang, H.-E., Yip, M.-K., Zeng, J., and Feng, T.-Y.(2005).
Expression of the hypersensitive response-assisting protein in Arabidopsis results in harpin-dependent hypersensitive cell death in response to Erwinia carotovora. Plant Mol. Biol. 59, 771-780.
Huang, H.-E., Ger, M.-J., Chen, C.-Y., Yip, M.-K., Chung, M.-C., and Feng, T.-Y.(2006).
Plant ferredoxin-like protein (PFLP) exhibits an anti-microbial ability against soft-rot pathogen Erwinia carotovora subsp. carotovora in vitro and in vivo. Plant Sci. 171, 17-23.
Huang, H.-E., Ger, M.-J., Chen, C.-Y., Pandey, A.-K., Yip, M.-K., Chou, H.-W., and Feng, T.-Y.(2007).
Disease resistance to bacterial pathogens affected by the amount of ferredoxin-I protein in plants. Mol. Plant Pathol. 8, 129-137.
Huang, H.-E., Liu, C.-A., Lee, M.-J., Kuo, C.-G., Chen, H.-M., Ger, M.-J., Tsai, Y.-C., Chen, Y.-R., Lin, M.-K., and Feng, T.-Y.(2007).
Resistance enhancement of transgenic tomato to bacterial pathogens by the heterologous expression of sweet pepper ferredoxin-I protein. Phytopathol. 97, 900-906.
Yip, M.-K., Huang, H.-E., Ger, M.-J., Chiu, S.-H., Tsai, Y.-C., Lin, C.-I., and Feng, T.-Y. (2007).
Production of soft rot resistant calla lily by expressing a ferredoxin-like protein gene (pflp) in transgenic plants. . Plant Cell Rep. 26, 449-457.
Patents
Lin, H.-J., and FENG, T.-Y. (1999. Oct.).
The use of a ferredoxin-like gene to protect plants against bacterial diseases. (USA patent) patent no. 5968804
Lin, H.-J., and FENG, T.-Y.(2001. Oct 2.).
The use of a ferredoxin-like gene to protect plants against bacterial diseases. (USA patent) patent no. 6297360.
