Dual RNA-Seq Analysis Pinpoints a Balanced Regulation Between Symbiosis and Immunity in - Symbiotic Nodules

Legume-rhizobial symbiosis initiates the formation of root nodules, within which rhizobia reside and differentiate into bacteroids to convert nitrogen into ammonium, facilitating plant growth. This process raises a fundamental question: how is plant immunity modulated within nodules when exposed to a substantial number of foreign bacteria? In , a mutation in the () gene exclusively results in the formation of necrotic nodules combined with activated immunity, underscoring the critical role of in suppressing immunity within nodules. In this study, we employed a dual RNA-seq transcriptomic technology to comprehensively analyze gene expression from both hosts and symbionts in the mutant nodules at different developmental stages (6 dpi and 10 dpi). We identified 89 differentially expressed genes (DEGs) related to symbiotic nitrogen fixation and 89 DEGs from associated with immunity in the nodules. Concurrently, we identified 27 rhizobial DEGs in the and genes of . Furthermore, we identified 56 DEGs from that are related to stress responses to ROS and NO. Our analyses of nitrogen fixation-defective plant mutants with overactivated defenses suggest that the host employs plant immunity to regulate the substantial bacterial colonization in nodules. These findings shed light on the role of in inhibiting the plant's immune response to maintain numerous rhizobial endosymbiosis in nodules.