Mei Phing Lee,3
Lila O. Vodkin,3
Steven J. Clough,3,5 and
1National Center for Soybean Biotechnology, Divisions of Plant Sciences and Biochemistry, University of Missouri, Columbia, MO 65211, U.S.A.; 2Department of Plant Science, Seoul National University, Seoul, The Republic of Korea; 3Department of Crop Sciences, University of Illinois, Urbana, IL 61801, U.S.A.; 4Computer Science Department, University of Missouri, Columbia, MO 65211, U.S.A.; 5United States Department of Agriculture-Agricultural Research Service, Urbana, IL 61801, U.S.A.
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Accepted 10 January 2008.
Legumes interact with nodulating bacteria that convert atmospheric nitrogen into ammonia for plant use. This nitrogen fixation takes place within root nodules that form after infection of root hairs by compatible rhizobia. Using cDNA microarrays, we monitored gene expression in soybean (Glycine max) inoculated with the nodulating bacterium Bradyrhizobium japonicum 4, 8, and 16 days after inoculation, timepoints that coincide with nodule development and the onset of nitrogen fixation. This experiment identified several thousand genes that were differentially expressed in response to B. japonicum inoculation. Expression of 27 genes was analyzed by quantitative reverse transcriptase-polymerase chain reaction, and their expression patterns mimicked the microarray results, confirming integrity of analyses. The microarray results suggest that B. japonicum reduces plant defense responses during nodule development. In addition, the data revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational, post-translational) that is likely essential for development of the symbiosis and adjustment to an altered nutritional status.
© 2008 The American Phytopathological Society