Systematic Screening of Host Interactors for Soybean Mosaic Virus Proteins Identifies Four Soybean (Glycine max) Antiviral Factors

Soybean mosaic virus (SMV) establishes successful infection through the coordinated action of multiple viral proteins, yet how these components are collectively engaged in host processes remains unclear. Using 10 SMV-encoded proteins as baits, we screened a soybean(Glycine max) cDNA library using the yeast two-hybrid (Y2H) method and obtained 200 positive clones corresponding to 147 nonredundant candidate host proteins. Integrative analyses indicated that these interacting proteins were mainly associated with host processes related to photosynthesis and energy metabolism, as well as protein quality control (PQC), and that their promoters were enriched in light- and stress-responsive elements. Photosynthesis-related genes were more strongly perturbed in the susceptible cultivar, whereas PQC-module genes showed overall downregulation in both resistant and susceptible cultivars upon SMV infection. Y2H, Bimolecular Fluorescence Complementation (BiFC), and transient expression assays identified four soybean resistance factors that interact with SMV proteins. These factors delayed systemic spread and continued to restrict viral proliferation after systemic infection was established. Notably, SMV accumulation partially rebounded when viral proteins were co-expressed with GmSTOP1, GmHrBP1, or GmGIP2, while co-expression of GmSiPPase and NIa-Pro further inhibited viral proliferation. In summary, this study maps the host-targeting profile of SMV across multiple viral components and provides clues to the SMV–soybean interaction network and antiviral gene resources in soybean.