Submitted to: International Conference on Legume Genomics and Genetics
Publication Type: Abstract Only
Publication Acceptance Date: 6/30/2002
Publication Date: N/A
Technical Abstract: Microarray analysis was used to examine genetic responses associated with nodulation in soybeans. The roots of five day old seedlings were inoculated with Bradyrhizobium japonicum and were harvested at 0, 3, 6, 12, 24, 48, and 72 hours after inoculation. Harvested roots were immediately frozen in liquid nitrogen and treated for RNA extraction in Trizol reagent. RNA from inoculated and mock-inoculated controls was pooled from approximately five plants for each time point and labeled with either dUTP-Cy**2 or dUTP-Cy**5 using reverse transcriptase. All samples were reverse labeled hybridized on cDNA microarrays representing 4,089 different soybean ESTs from a seven day old soybean, uninoculated root cDNA library. Our analysis revealed that only about 0.5 percent of the genes spotted were affected by inoculation indicating that early events in nodulation did not trigger a massive response from genes involved in normal root development and function. However, the arrays did identify an increased expression of a couple of genes homologous to pathogenicity-related proteins and of ENOD36A, a gene that had previously been implicated in nodulation.