Differential Gene Expression Profiling in Soybean to Investigate the Relationship Between Nitrogen Fixation and Drought Stress

Drought is a major constraint in soybean (Glycine max) agriculture. Soybean plants obtain nitrogen through nitrogen fixation (N-fixation), a process that is sensitive to water deficit. Reliance on N-fixation as a source of nitrogen thus makes soybean plants vulnerable to nitrogen deficiency during periods of drought. Since soybean genotypes differ in N-fixation efficiency and in N-fixation sensitivity to drought, improving N-fixation tolerance to water deficit is an approach used in breeding programs to improve soybean crop performance. Identification of genes involved in the response of N-fixation to water deficit will provide candidate loci for marker development. We have used RNAseq to investigate the effects of water deficit on gene expression in high and low nitrogen fixing cultivars. We exposed two soybean cultivars to varying moisture level conditions (well-watered, moderate water stress and severe water stress) and extracted RNA from three tissues (leaves, roots, and root nodules) for sequencing using Illumina Hi-Seq (100 bp single-end reads). Reference-based transcript assembly followed by differential gene expression analysis will provide insights into the relationship between N-fixation and drought, and may provide candidate genes as sources of markers for use in crop improvement programs.