Office: 226 Schweitzer Hall
117 Schweitzer Hall
University of Missouri
Columbia, MO 65211
|BS||University of Wisconsin||Madison, Wis.||Biochemistry|
|PhD||University of Wisconsin||Madison, Wis.||Biochemistry|
Biochemical regulation of Bradyrhizobium japonicum during symbiotic development.
Biochemical and genetic regulation of the metabolic processes that are required for symbiotic nitrogen fixation is the focus of this research program. Rhizobium-leguminous plant symbioses are unique associations in which both the bacteria and the plant undergo complex metabolic and morphological changes. My laboratory is attempting to identify these processes and to elucidate the mechanisms by which these changes are controlled. The primary goal is to determine which factors, genetic and/or biochemical, limit nitrogen fixation and thus plant growth and development. After these limitations are defined, the appropriate generic alterations will then be attempted to enhance plant productivity.
A recent focus of the laboratory has been the elucidation of malate metabolism by the symbiotic form of B. japonicum which are referred to as bacteroids and the role of alanine excretion by bacteroids. Malate is the primary compound provided to the bacterorid by the plant and is believed to be metabolized via the citric acid cycle, but we have shown that neither α-ketoglutarate dehydrogenase nor isocitrate dehydrogenase are required for symbiotic nitrogen fixation. Thus, the pathway of malate metabolism to provide energy for reduction of atmospheric dinitrogen remains to be determined. Recently, we have shown that alanine, not ammonium, is the principle nitrogen compound provided to the plant by the bacteroid. The metabolism of B. japonicum is being characterized via DNA microarray and proteomic analysis.
Jeon JM, Lee HI, Donati AJ, So JS, Emerich DW, Chang WS. Whole-genome expression profiling of Bradyrhizobium japonicum in response to hydrogen peroxide. Mol Plant Microbe Interact. 2011 Dec;24(12):1472-81. doi: 10.1094/MPMI-03-11-0072.
Sarma A.D., Oehrle N.W., Emerich D.W. Plant protein isolation and stabilization for enhanced resolution of two-dimensional polyacrylamide gel electrophoresis. Anal. Biochem. 379 (2): 192-5 (2008).
Oehrle N.W., Sarma A.D., Waters J.K., Emerich D.W. Proteomic analysis of soybean nodule cytosol. Phytochemistry. 69 (13): 2426-38 (2008).
Chang W.S., Franck W.L., Cytryn E., Jeong S., Joshi T., Emerich D.W., Sadowsky M.J., Xu D., Stacey G. An oligonucleotide microarray resource for transcriptional profiling of Bradyrhizobium japonicum. Mol. Plant Microbe Interact. 20 (10): 1298-307 (2007).
N.W. Oehrle, L.S. Green, D.B. Karr and D.W. Emerich. The HFC/HCFC breakdown product of trifluoroacetic acid (TFA) and its effects on the symbiosis between Bradyrhizobium japonicum and soybean (Glycine max). Soil Biol. Biochem. 36:333-342 (2004).
D.B. Karr, N.W. Oehrle and D.W. Emerich. Recovery of nitrogenase from aerobically isolated soybean nodule bacteroids. Plant and Soil. 257:27-33 (2003).
L.S. Green, J. K. Waters, S. Ko, and D.W. Emerich. Comparative analysis of the Bradyrhizobium japonicum sucA region. Can. J. Microbiol. 49:237-243 (2003).