Rice Orange Leaf Phytoplasma Imp Protein Blocks G–M Interaction by Binding Glycoprotein G to Suppress Rice Stripe Mosaic Virus Infection

Plants frequently encounter multiple pathogens concurrently, yet the molecular bases of pathogen-pathogen interactions during mixed infections remain largely unresolved. Here we show that co-infection of rice by Rice orange leaf phytoplasma (ROLP) and Rice stripe mosaic virus (RSMV) markedly suppresses RSMV proliferation in both host plants and the insect vector. Electron microscopy and confocal imaging reveal that ROLP and RSMV co-inhabit individual rice phloem cells and undergo close membrane interaction, producing swollen RSMV virions with reduced infectivity. We further demonstrate that the ROLP membrane protein Imp interacts with the RSMV G envelope protein and competitively disrupts the G-M association essential for virion assembly. The Imp region encompassing residues 96-122 (Imp-α4) is necessary for this inhibition. Transgenic rice overexpressing Imp or Imp-α4 phenocopies these effects, displaying deformed virions and diminished viral load. These findings uncover a cross-kingdom antagonistic mechanism between two phylogenetically distant pathogens and offer conceptual directions for engineering durable antiviral resistance.