Fig 7. A model illustrates how NbMIP1s, autophagy, and the UPR regulate RSV infection.

First, the ribonucleoprotein complex (RNP) of RSV enters a plant cell through PD. RSV infection elicits the UPR. Then, the autophagy pathway is activated by the UPR to promote the degradation of RSV NSvc4. As a counter-response, NSvc4 hijacks NbMIP1 family proteins (or OsDjA5 in rice) which are also upregulated by UPR, to protect NSvc4 itself from autophagic degradation. The stabilized NSvc4 binds the genome of RSV and facilitate it going through the PD to the next cell. However, the exact mechanisms about how NSvc4 is transported to autophagosomes and how NbMIP1s protect NSvc4 from autophagic degradation need further investigation. ER, endoplasmic reticulum; PM, plasma membrane; PD, plasmodesma.