Identification of Soybean Genes Correlated with Rhizobial Nitrogen Fixation Activity

Abstract

Abstract Background and Aims Soybean (Glycine max L.) has the ability to establish a symbiotic relationship with rhizobia. However, little is known about the host plant genes that correlate with the nitrogen fixation activity of rhizobia. Methods Herein, soybean seeds were inoculated with two strains of wild-type soybean rhizobia with different nitrogen fixation activities and grown in the field until the R1 stage. Results Thereafter, the roots and nodules were subjected to RNA-Seq to detect the expression of soybean genes related to nitrogen fixation, followed by the analysis of the community structure of the soybean-nodulating rhizobia. GmNRT2.5, a high-affinity nitrate transporter gene, was correlated with nitrogen fixation activity. Real-time PCR analysis of the roots and nodules inoculated with a nod+/fix-(Δnif genes) mutant rhizobia showed that GmNRT2.5on chromosome 8 (Glyma.08G284000: GmNRT2.5 Chr8) was especiallycorrelated with nitrogen fixation activity. Conclusion GmNRT2.5Chr8 acts as a switching strategy between nitrogen fixation and acquisition from the soil. We also found that GmNRT2.5 Chr8 is a useful host gene that acts as an indicator of nitrogen fixation activity.