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Research Interests
- Molecular interaction between rice and Xanthomonas oryzae pv. Oryzae
- Metabolic engineering of fatty acid/lipid biosynthesis in Jatropha (Jatropha curcas L.) and generation of transgenic Jatropha deficient in curcin
Research Interest :
Molecular interaction between rice and Xanthomonas oryzae pv. Oryzae
Research areas
- Molecular plant-microbe interaction using rice and Xanthomonas oryzae pv. oryzae as model system
- Cloning of disease resistance (R) genes to bacterial blight from rice
- Identification of genes involved in disease resistance pathway(s)
- Engineering enhanced and broad-spectrum disease resistance to bacterial blight in rice
Bacterial blight (Figure 1), a disease affecting rice and caused by X. oryzae pv. oryzae (Figure 2), is a significant agronomic problem in many rice-growing regions. Use of resistant varieties is the most economic and effective method to control the disease. Race-specific interaction between rice and X. oryzae pv. oryzae is thought to follow the classical gene-for-gene concept, in which the plant resistance (R) gene can recognize or interact with an elicitor molecule encoded by an avirulence (Avr) gene from the pathogen. The recognition and interaction lead to activation of a cascade of defense responses and effectively inhibit pathogen invasion.
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through
hydathode. Photo was provided by J. Leach.
We recently cloned a bacterial blight R gene, Xa27, from rice. We found that the induction of Xa27 occurs only in the immediate vicinity of infected tissue upon inoculation with incompatible X. oryzae pv. oryzae strains. We then isolated the cognate Avr gene, AvrXa27, from the incompatible strain PXO99A by collaborating with Dr. White’s lab (http://www.oznet.ksu.edu/plantpath/whiteslab/welcome.htm). AvrXa27 encodes a typical nuclear localized type-III effector. We found that Xa27 expression induced by AvrXa27 triggered disease resistance to bacterial blight in rice. Our findings indicate that Xa27 mediates resistance by a previously unknown mechanism, and that specificity towards incompatible pathogens involves the differential expression of the R gene in the presence of the AvrXa27 effector (Figure 3).
We currently are employing approaches related to genetics, molecular and cellular biology to perform detailed functional analysis of Xa27 and AvrXa27, and to study their interaction in signal transduction pathway of rice disease resistance. The current research activities are
1. Subcellular localization of Xa27 and its biochemical function
2. Function of AvrXa27 in transcriptional regulation of Xa27
3. Relationship between Xa27-mediated disease resistance and SA-, JA- and Ethylene-mediated signal transduction pathways
PXO99A
Research Interest II:
Metabolic engineering of fatty acid/lipid biosynthesis in Jatropha (Jatropha curcas L.) and generation of transgenic Jatropha deficient in curcin
Jatropha is a small tropical, woody plant of the Euphorbiaceae family. Jatropha seeds contain as much as 40% of oil which is mainly stored in endosperm. The oil from Jatropha is a potential bioenergy source which can serve as substitute for diesel fuel. Therefore it is not surprising that several developing countries are now promoting Jatropha as the future biodiesel crop.
Results in the last decade have demonstrated the possibility to increase the yield of oil from oilseed crops through transgenesis. We firstly studied the development of seed, endosperm and oil bodies of Jatropha using transmission electron microscopy (TEM). This information on endosperm and oil development of Jatropha seeds greatly facilitated the study of gene expressions that are involved in biosynthesis of storage lipids. Through molecular and genomic approaches, we are isolating the key genes which are involved in de novo fatty acid/lipid biosynthesis. We aim to genetically engineer fatty acids (FA)/lipid biosynthesis in Jatropha seeds to increase oil yield and unsaturated FA in storage lipids.
In addition, we are exploring the generation of new Jatropha varieties which are deficient in curcin in the seeds through transgenic technology. Curcin is recognized as a toxic protein specifically expressed in Jatropha seeds. It is one of the several toxic components which prevent Jatropha seeds to be used as animal feed.
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