My laboratory studies the molecular mechanisms underlying bacteria-plant interactions.  Specially, we are interested in elucidating the strategies employed by bacteria to facilitate the establishment and maintenance of the symbiotic relationship with plant hosts.

Our main focus is to characterize a specialized protein secretion system in plant-associating bacteria - the type III secretion system. Type III secretion system is a key pathogenicity determinant in gram negative bacterial pathogens responsible for some of the most devastating diseases on animals and plants.  This needle-like type III secretion apparatus spans the cell membranes of the pathogens and the hosts, and injects multiple proteins, called the type III secreted effectors (T3SEs), directly into the host cell cytoplasm. T3SEs directly interact with their host substrates and contribute to disease development.  During the arms race between pathogens and plants, plant evolved resistance (R) genes that recognize specific T3SEs and trigger defense responses.  This effector-triggered immunity (ETI) could be evaded by the pathogens in order to regain the ability to cause diseases.

       My laboratory aims to understand the functionality of T3SEs in pathogenic bacteria, mainly the plant pathogen Pseudomonas syringae, during their interactions with plant hosts.  A combination of comparative genomic, functional genomic, genetic, biochemical and bioinformatic approaches are employed. Novel knowledge obtained from our research will contribute to the development of sustainable control strategies against bacterial diseases.

1.  Zhou, H., Morgan, R.L., Guttman, D.S. and Ma, W. 2009. Allelic variants of the Pseudomonas syringae type III effector HopZ1 are differentially recognized by plant resistance systems. Mol. Plant-Microbe Interact. 22: 176-189.

2.  Ma, W. and Guttman, D.S. 2008. Evolution of prokaryotic and eukaryotic virulence effectors.  Curr. Opin. Plant Biol. Doi:10.1016/j.pbi.2008.05.001.

3.  Lewis, J.D., Abada, W., Ma, W., Guttman, D.S. and Desveaux, D. 2008. The HopZ family of Pseudomonas syringae type III effectors require myristoylation for virulence and avirulence functions in Arabidopsis. J. Bacteriol. 190: 2880-2891.

4.  Ma, W., Dong, F.F.T, Stavrinides, J. and Guttman, D.S. 2006. Type III effector diversification via both pathoadaptation and horizontal transfer in response to a coevolutionary arms race. PLoS Genetics. 2(12): e209.DOI.

5.  Stavrinides, J.*, Ma, W.* and Guttman, D.S. 2006. Terminal reassortment drives the quantum evolution of type III effectors in bacterial pathogens. PLoS Pathog. 2(10): e104.DOI. (* co-first author)

6.  Ma, W., Charles, T.C. and Glick, B.R. 2004. Expression of an exogenous 1-aminocyclopropane-1-carboxylate deaminase gene in Sinorhizobium meliloti increases its ability to nodulate alfalfa. Appl. Environ. Micriobiol. 70: 5891-5897.

7.  Ma, W., Guinel, F.C. and Glick, B.R. 2003. Rhizobium leguminosarum bv. viciae 1-aminocyclopropane-1-carboxylate deaminase promotes nodulation of pea plants. Appl. Environ. Microbiol. 69: 4396-4402.

8.  Ma, W., Sebestianova, S., Sebestian, J., Burd, G.I., Guinel, F.C. and Glick, B.R. 2003. Prevalence of 1-aminocyclopropane-1-carboxylate deaminase in Rhizobia spp.. Antonie van Leeuwenhoek 83: 285-291.

9.  Ma, W., Penrose, D.M. and Glick, B.R. 2002. The effect of ethylene on the nodulation of legumes. Can. J. Microbiol. 48: 947-954.

10. Ma, W., Zalec, K. and Glick, B.R. 2001. Biological activity and colonization pattern of the bioluminescence labeled plant growth-promoting bacterium Kluyvera ascorbata SUD165/26. FEMS Microbiol Ecol. 35: 137-144.

11. Zhang, J., Ma, W. and Tan, H. 2002. Cloning, expression and characterization of a gene encoding nitroalkane-oxidizing enzyme from Streptomyces ansochromogenes. Eur. J. Biochem. 269: 6302-6307.

12. Glick, B.R., Penrose, D.M. and Ma, W. 2001. Bacterial promotion of plant growth. Biotechnol. Adv. 19: 135-138.

13. Tan, H., Yang, H., Tian Y, Ma, W., and Liu, G.  1998.  Structure and function of saw1- a gene related to differentiation of Streptomyces ansochromogenes.  Acta Microbiologica Sinica, 38(6): 435-440.