GmRAC1 is a positive regulator symbiosis-promoting effects of the type III effector NopC and improves grain yield in soybean (PRJCA044488)

Type III effectors (T3Es) play a crucial role in the establishment of symbiotic interactions between leguminous plants and rhizobia. However, the molecular functions of most T3Es, as well as the regulatory and molecular mechanisms underlying their symbiotic effects on leguminous hosts, remain unclear. Here we describe a high conservation T3E Nodulation Outer Protein C (NopC) in Sinorhizobium fredii HH103, whose symbiotic promotion effect is influenced by GmRAC1, a ROP/RAC family GTPase in soybeans. GmRAC1 physically interacts with NopC and affects the expression of symbiosis-related genes GmNIN2s and GmENOD40. Silencing GmNIN2a and GmNIN2b results in NopC not promoting symbiosis. In additions, the promoter variation of GmRAC1 dictates the symbiotic contribution of NopC during symbiotic establishment and it was strongly selected in soybean breeding. More importantly, overexpression of GmRAC1 in DN50 increases 100-seed weight and yield. Thus, our findings identify GmRAC1 as a key regulator of NopC-mediated symbiosis promotion effect, and offers translational potential for enhancing symbiotic nitrogen fixation in molecular breeding of soybean.