Loss-of-Function of Two PD-Associated Proteins Confers Resistance to Rice Stripe Virus

Plant viruses usually exploit plasmodesmata (PDs) to achieve cellular infection in host plants. Although PD-associated proteins are commonly implicated in the regulation of PD pore size, a few limited cases demonstrate their roles as viral targets suitable for resistance breeding. Here we screened the importin α protein family of rice to identify the PD-associated members and explored their effects on the infection of rice stripe virus (RSV), one of the most notorious pathogens threatening rice yields. Both Importin α1b and α4 were found to be localised on the plasma membrane and PD. Only importin α4 knockout mutant rice exhibited resistance to RSV infection while the role of importin α1b in RSV infection was negligible. The absence of importin α4 enhanced callose deposition at PDs, which impeded viral intercellular movement. Flotillin 1 is another PD-associated protein in rice and was previously reported to facilitate RSV infection. When flotillin1 and importin α4 were simultaneously knocked out, the double-knockout mutant exhibited a synergically higher resistance level to RSV not only in the greenhouse but also in natural fields without affecting agronomic traits. This study proposed the potential of the two PD-associated proteins as targets for engineering virus resistance in future.