Research Interests:
Efforts in my laboratory are focused in two areas. We are interested in isolating and characterizing genes from plant pathogens that have potential usefulness in the genetic engineering of disease-resistant plants. Our major effort is directed at developing strategies for engineering resistance to a group of fungal plant pathogens (Cercospora species) which parasitize plants by producing a photoactivated, active-oxygen-producing toxin. We have developed several strategies to identify from the fungus, genes that encode resistance to the toxin. Isolated genes are being characterized for function and for their ability to impart resistance in transgenic plants. Efforts are also ongoing in the lab to isolate and characterize genes from bacteria that encode toxin degradation, as such genes may also be useful strategy for obtaining disease resistance. In addition, we are interested in active oxygen species, their varied roles in plant-pathogen interactions, and antioxidant defenses in plants. We are defining the role of pyridoxine (vitamin B6) in active oxygen resistance and the regulation of pyridoxine biosynthetic genes during plant biotic and abiotic stress responses using Arabidopsis and tobacco as models. We are also studying the possible importance of mannitol biosynthesis in protecting fungal plant pathogens against plant oxidative defenses.

For further information on specific projects on-going in the Daub Lab click here.

Recent Publications:

Gonzalez, E., Danehower, D., and Daub, M. E.  2007.  Vitamer levels, stress response, enzyme activity, and gene regulation of Arabidopsis lines mutant in the pyridoxine/pyridoxamine 5’-phosphate oxidase (PDX3) and the pyridoxal kinase (SOS4) genes involved in the vitamin B6 salvage pathway.  Plant Physiol. (In Press).

Herrero, S., Amnuaykanjanasin, A., and Daub, M. E.  2007.  Identification of genes differentially expressed in the phytopathogenic fungus Cercospora nicotianae between cercosporin toxin-resistant and -susceptible strains.  FEMS Microbiol. Lett.  275:326-337.

Chen, H., Lee, M. H., Daub, M. E., and Chung, K. R.  2007.  Molecular analysis of the cercosporin biosynthetic gene cluster in Cercospora nicotianae. Molec. Microbiol. 64:755-770.

Denslow, S. A., Rueschhoff, E. E., and Daub, M. E.  2007. Regulation of the Arabidopsis thaliana vitamin B6 biosynthesis genes by abiotic stress.  Plant Physiol. Biochem. 45:152-161.

Herrero, S. and Daub, M. E. 2007. Genetic manipulation of vitamin B6 biosynthesis in tobacco and fungi uncovers limitations to up-regulation of the pathway.  Plant Sci. 172:609-620.

Velez, H., Glassbrook, N. J., and Daub, M. E.  2007.  Mannitol metabolism in the phytopathogenic fungus Alternaria alternata.  Fungal Genet. Biol. 44:258-268.

Taylor, T. V., Mitchell, T. K., and Daub, M. E.  2006.  An oxidoreductase is involved in cercosporin degradation by the bacterium Xanthomonas campestris pv. zinniae.  Appl. Environ. Microbiol. 72:6070-6078.

Choquer, M., Dekkers, K. L., Chen, H. Q., Cao, L., Ueng, P. P., Daub, M. E., and Chung, K. R.  2005.  The CTB1 gene encoding a fungal polyketide synthase is required for cercosporin biosynthesis and fungal virulence of Cercospora nicotianae.  Molec. Plant Microbe Interact. 18:468-476.

Denslow, S. A., Walls, A. A., and Daub, M. E.  2005.  Regulation of biosynthetic genes and antioxidant properties of vitamin B6 vitamers during plant defense responses.  Physiol. Molec. Plant Pathol. 66:244-255.

Daub, M. E., Herrero, S., and Chung, K. R.  2005.  Photoactivated perylenequinone toxins in fungal pathogenesis of plants.  FEMS Microbiol. Lett. 252:197-206.

Wetzel, D.K., Ehrenshaft, M., Denslow, S. A., and Daub, M. E. 2004.  Functional complementation between the PDX1 vitamin B6 biosynthetic gene of Cercospora nicotianae and pdxJ of Escherichia coli. FEBS Lett. 564: 143-146.

Mitchell, T. K., Alejos-Gonzalez, F., Gracz, H. S., Danehower, D. A., Daub, M. E., and Chilton, W. S.  2003. Xanosporic acid, an intermediate in bacterial degradation of the fungal phototoxin cercosporin.  Phytochemistry 62:723-732.

Chung, K. R., Daub, M. E., Kuchler, K., and Schuller, C. 2003.  The CRG1 gene required for resistance to the singlet oxygen-generating cercosporin toxin in Cercospora nicotianae encodes a putative fungal transcription factor.  Biochem. Biophys. Res Commun. 302:302-310.  
           
Chung, K. R., Ehrenshaft, M., and Daub, M. E.  2003.  Expression of the cercosporin toxin resistance gene CRG1 as a dicistronic mRNA in the filamentous fungus Cercospora nicotianae.  Current Genet. 43:415-424.

Chung, K. R., Ehrenshaft, M., Wetzel, D. K., and Daub, M. E.  2003.  Cercosporin-deficient mutants by plasmid tagging in the asexual fungus Cercospora nicotianae.  Molec. Gen. Genomics 270:103-113.

Chung, K. R., Ehrenshaft, M., and Daub, M. E. 2002. Functional expression and cellular localization of cercosporin-resistance proteins fused with GFP in Cercospora nicotianae.  Curr. Genet. 41:159-168.

Mitchell, T. K., Chilton, W. S., and Daub, M. E. 2002.  Biodegradation of the polyketide toxin cercosporin.  Appl. Environ. Microbiol. 68:4173-4181.

Jennings, D. B., Daub, M. E., Pharr, D. M., and Williamson, J. D. 2002.  Constitutive expression of a celery mannitol dehydrogenase in tobacco enhances resistance to the mannitol-secreting fungal pathogen Alternaria alternata.  Plant J 32:41-49.

Bilski, P., Daub, M. E., and Chignell, C. F.  2002.  Direct detection of singlet oxygen via its phosphorescence from cellular and fungal cultures.  Methods Enzym. 352:41-52.
           
Herrero, S. Rufty, R.C., and Daub, M.E.  2001. Molecular determinants influencing the inheritance of transgenic virus resistance in segregating tobacco families transformed with the nucleocapsid gene of tomato spotted wilt virus.  Molec. Breeding 7:131-139.

Ehrenshaft, M., and Daub, M. E.  2001. Isolation of pdx2, a second novel gene in the pyridoxine biosynthetic pathway of eukaryotes, archaebacteria, and a subset of eubacteria.  J. Bact. 183:3383-3390.

Daub, M. E., Li, M., Bilski, P., and Chignell, C. F. 2000.  Dihydrocercosporin singlet oxygen production and subcellular localization: a possible defense against cercosporin phototoxicity in Cercospora.  Photochem. Photobiol. 71:135-140.

Bilski, P., Li, M. Y., Ehrenshaft, M., Daub, M. E., and Chignell, C. F.  2000. Vitamin B6 (pyridoxine) and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants.  Photochem. Photobiol. 71:129-134.

Herrero, S., Culbreath, A. K.,  Csinos, A. S., Pappu, H. R., Rufty, R. C., and Daub, M. E. 2000. Nucleocapsid gene-mediated transgenic resistance provides protection against tomato spotted wilt virus epidemics in the field.  Phytopathology 90:135-140.

Ehrenshaft, M., Daub, M. E., Bilski, P., Li, M. Y., Chignell, C. F., Jenns, A. E., and Chung, K. R.  2000.  A divergence in the biosynthetic pathway and a new role for vitamin B6.  pp. 17-22 In Biochemistry and Molecular Biology of Vitamin B6 and PQQ-dependent Proteins.  A. Iriarte, H. M. Kagan, and M. Martinez-Carrion, eds.  Birkhauser Verlag, Basel.

Daub, M. E. and Ehrenshaft, M.  2000.  The photoactivated Cercospora toxin cercosporin: contributions to plant disease and fundamental biology.  Annu. Rev. Phytopathol. 38:461-490.

Ehrenshaft, M., Chung, K. R., Jenns, A. E., and Daub, M. E.  1999.  Functional characterization of SOR1, a gene required for resistance to photosensitizing toxins in the fungus Cercospora nicotianae.  Current Genetics 34:478-485.
 
Chung, K. R., Jenns, A. E., Ehrenshaft, M., and Daub, M. E.  1999. A novel gene required for cercosporin toxin resistance in the fungus Cercospora nicotianae.  Mol. Gen. Genet. 262:382-389.

Ehrenshaft, M., Bilski, P., Li, M., Chignell, C. F., and Daub, M. E.  1999.  A highly conserved sequence is a novel gene involved in de novo vitamin B6 synthesis.  Proc. Natl. Acad. Sci. 96:9374-9378.

Sherman, J. M, Moyer, J. W., and Daub, M. E. 1998. A single high-efficiency regeneration and Agrobacterium-mediated transformation system for the genetic engineering of multiple chrysanthemum genotypes.  J. Am. Soc. Hort. Sci. 123:189-194

Sherman, J. M., Moyer, J. W., and Daub, M. E.  1998.  Tomato spotted wilt virus resistance in chrysanthemum expressing the virual nucleocapsid gene.  Plant Dis. 82 :407-414.

Ehrenshaft, M., Jenns, A. E., Chung, K. R., and Daub, M. E. 1998. SOR1, a gene required for photosensitizer and singlet oxygen resistance in Cercospora fungi is highly conserved in divergent organisms.  Mol. Cell 1:603-609.

Daub, M. E., Ehrenshaft, M., Jenns, A. E., and Chung, K. R.  1998.  Active oxygen in fungal pathogenesis of plants: the role of cercosporin in Cercospora diseases.  pp. 31-56 In J. T. Romeo, K. R. Downum, and R. Verpoorte, eds.  Phytochemical Signals and Plant-Microbe Interactions, Recent Advances in Phytochemistry, Vol 32, Plenum Press, NY.