Plant potassium channel β -subunits confer antiviral defense via disrupting potyviral 6K2-mediated vesicle maturation and trafficking

Potyviruses constitute the largest known group of plant RNA viruses. Their 6K2 protein is an integral membrane protein that induces the formation of vesicular structures, which support viral RNA replication and act as vehicles for intracellular movement. While multiple host proteins are known to regulate either viral replication or movement, it remains largely unclear whether and how a single host protein can coordinately modulate both processes. Here, we identify NbKNB1, a Nicotiana benthamiana homolog of the plant potassium channel β-subunit. Genetic assays demonstrate that NbKNB1 confers antiviral activity against turnip mosaic virus (TuMV). NbKNB1 localizes predominantly to the plasma membrane in healthy cells, but relocalizes to 6K2-induced viral replication complexes during TuMV infection. Biochemical analyses show that NbKNB1 directly interacts with 6K2, disrupting 6K2 self-association and impairing the maturation of 6K2-tagged vesicles. NbKNB1 also competes with the viral cylindrical inclusion (CI) protein for 6K2 binding, thereby inhibiting TuMV cell-to-cell movement. A 6K2-binding-deficient mutant, NbKNB1Δ270-279, fails to restrict both viral replication and intercellular movement, confirming that direct interaction with 6K2 is required for NbKNB1-mediated suppression of TuMV infection. Moreover, NbKNB1 and its maize homolog ZmKZB1 also reduce infection by other potyviruses. Collectively, these findings reveal a novel antiviral strategy in which plant potassium channel β-subunit homologs target the viral 6K2 protein to counteract potyvirus infection, and provide a promising target for antiviral breeding.