Department of Microbiology and Cell Science University of Florida
Ph.D. (1999) Institute of Genetics, CAS, Beijing, China
Post-doctoral: (2000-2004) DCMB, Department of Biology, Duke University
Description of Research
General area: The signal transduction pathways in plant immunity
Like animals, plants have evolved active defense mechanisms to fight microbial infections. Following pathogen invasion, plants activate multiple signal transduction pathways to mount immunity against the pathogens. We study these signal transduction pathways and their activation mechanisms using the model plant Arabidopsis. Several projects are currently being carried out in the laboratory.
(1) Epigenetic regulation of plant immunity by the Elongator complex
Elongator is a six-subunit complex that has been shown to function in transcription elongation. We identified Elongator mutants (elp) in a genetic screen for suppressors of the npr1 mutant. NPR1 is a key regulator of salicylic acid (SA)-mediated defense responses. The npr1 mutant is completely defective in systemic acquired resistance (SAR), an inducible defense mechanism against a broad-spectrum of pathogens. We found that defense gene activation is delayed in the elp mutants (Defraia et al., 2010). The elp mutants are more susceptible to pathogen infection than wild type, demonstrating a positive role for Elongator in plant immunity. We are using chromatin immunoprecipitation (ChIP), bisulfite sequencing, and microarray to study the epigenetic regulation of defense gene expression by the Elongator complex.
(2) Regulation of plant immunity by extracellular pyridine nucleotides
Our laboratory found for the first time that extracellular NAD(P) activates SA/NPR1-dependent defense responses (Zhang et al., 2009). We are using genetic approaches to identify new components in the extracellular NAD(P)-mediated defense signaling pathway.
(3) Regulation of SA accumulation during pathogen infection
Plants synthesize multiple signal molecules to activate defense responses at and surrounding infection sites. One such signal molecule is SA. Although two mutants that are unable to accumulate SA upon pathogen infection have been identified, it is still not completely understood how SA accumulation is regulated. Our laboratory has developed a high-throughput method for isolation of SA metabolic mutants (Defraia et al., 2008; Marek et al., 2010). Using this method, we are screening for suppressors of npr1, a mutant that accumulates significantly higher levels of SA than wild type. These mutants will be valuable for dissecting the SA-mediated signaling pathway.
(4) Engineering SAR in crop plants
We apply the knowledge gained from the model plant Arabidopsis to agriculturally important crop plants such as citrus. We have transformed the SAR key regulator NPR1 into citrus and found that the transgenic plants exhibited increased resistance to citrus canker (Zhang et al., 2010). We are currently studying/engineering the SAR signaling pathway in citrus to increase resistance to canker and greening, two major diseases threatening Florida’s citrus industry.
- Wang, Y., An, C., Zhang, X., Yao, J., Zhang, Y., Sun, Y., Yu, F., Amador, D.M. and Mou, Z. (2013). The Arabidopsis Elongator complex subunit2 epigenetically regulates plant immune responses. Plant Cell 25, 762-776.
- Zhang, X., Wang, C., Zhang, Y., Sun, Y. and Mou, Z. (2012). The Arabidopsis Mediator complex subunit16 positively regulates salicylate-mediated systemic acquired resistance and jasmonate/ethylene-induced defense pathways. Plant Cell 24, 4294-4309.
- Zhang, X. and Mou, Z. (2012). Expression of the human NAD(P)-metabolizing ectoenzyme CD38 compromises systemic acquired resistance in Arabidopsis. Molecular Plant-Microbe Interactions 25, 1209-1218.
- An, C. and Mou, Z. (2012). Non-host defense response in a novel Arabidopsis-Xanthomonas citri subsp. Citri pathosystem. PLoS ONE 7(1): e31130.
- Defraia, T.C., Zhang X. and Mou, Z. (2010). Elongator subunit 2 is an accelerator of immune responses in Arabidopsis thaliana. Plant Journal 64, 511-523.
- Zhang, X., Francis, M.I., Dawson, W.O., Graham, J.H., Orbović, V., Triplett, E.W. and Mou, Z. (2010). Overexpression of the Arabidopsis NPR1 gene in citrus increases resistance to citrus canker. European Journal of Plant Pathology 128, 91-100.
- Zhang, X., Chen, S. and Mou, Z. (2010). Nuclear localization of NPR1 is required for regulation of salicylate tolerance, isochorismate synthase 1 expression and salicylate accumulation. Journal of Plant Physiology 167, 144-148.
- Xiong, Y., DeFraia, C., Williams, D., Zhang, X. and Mou, Z. (2009). Deficiency in a cytosolic ribose-5-phosphate isomerase results in chloroplast dysfunction, late flowering and premature cell death in Arabidopsis. Physiologia Plantarum 137, 249-263.
- Xiong, Y., DeFraia, C., Williams, D., Zhang, X. and Mou, Z. (2009). Characterization of Arabidopsis 6-phosphogluconolactonase T-DNA insertion mutants reveals an essential role of the oxidative section of the plastidic pentose phosphate pathway in plant growth and development. Plant & Cell Physiology 50, 1279-1291.
- Spoel, S.H.*, Mou, Z.*, Tada, Y., Spivey, N.D., Genschik, P. and Dong, X. (2009). Proteasome-mediated turnover of the transcription co-activator NPR1 plays dual roles in regulating plant immunity. Cell 137, 860-872. *authors with equal contributions.
- Zhang, X. and Mou, Z. (2009). Extracellular pyridine nucleotides induce PR gene expression and disease resistance in Arabidopsis. Plant Journal 57, 302-312.
- Defraia, T.C., Schmelz, E.A. and Mou, Z. (2008). A rapid biosensor-based method for quantification of free and glucose-conjugated salicylic acid. Plant Methods 4, 28.
- Tada, Y., Spoel, S.H., Pajerowska-Mukhtar, K., Mou, Z., Song, J. and Dong, X. (2008). S-nitrosylation and thioredoxins regulate conformational changes of NPR1 in establishing plant immunity. Science 321, 952-956.
- Zhang, X., Dai, Y., Xiong, Y., Defraia, C., Li, J., Dong, X. and Mou, Z. (2007). Overexpression of Arabidopsis MAP Kinase Kinase 7 leads to activation of plant basal and systemic acquired resistance. Plant Journal 52, 1066-1079.
- Dai, Y., Wang, H., Li, B., Huang, J., Liu, X., Zhou, Y., Mou, Z. and Li, J. (2006). Increased expression of MAP Kinase Kinase 7 causes deficiency in polar auxin transport and leads to plant architectural abnormality in Arabidopsis thaliana. Plant Cell 18, 308-320.
- Mou, Z., Fan, W. and Dong X. (2003). Inducers of plant systemic acquired resistance regulate NPR1 function through redox changes. Cell 113, 935-944.
- Mou, Z., Wang, X., Fu, Z., Dai, Y., Han, C., Ouyang, J., Bao, F., Hu, Y. and Li, J. (2002). Silencing of phosphoethanolamine N-methyltransferase results in temperature-sensitive male sterility and salt hypersensitivity in Arabidopsis. Plant Cell 14, 2031-2043.
- Mou, Z., He, Y., Dai, Y., Liu, X. and Li, J. (2000). Deficiency in fatty acid synthase leads to premature cell death and dramatic alterations in plant morphology. Plant Cell 12, 405-417.