Small heat shock and J-domain proteins direct defense against areca palm velarivirus 1 by degrading coat protein via autophagy.

Both autophagy and heat shock proteins (HSPs) play dual roles in viral infections, yet their coordination in antiviral defense remains unclear. Here, we show that a cytosolic small heat shock protein (AcsHSP) and a type II J-domain protein (AcDNAJB13) from areca palm interact with the coat protein (CP) of areca palm velarivirus 1 (APV1) independently of HSP70 chaperones. Their closest Nicotiana benthamiana homologs also bind CP. Both APV1 infection and CP expression induces the transcription of sHSP and DNAJB13, which in turn inhibits CP accumulation. Silencing of these genes enhances APV1 infection and CP accumulation, while overexpression of AcsHSP reduces viral accumulation. Mechanistically, CP is degraded via autophagy. Both AcsHSP and AcDNAJB13 interact with the autophagosome marker ATG8f1. However, AcsHSP strengthens CP-ATG8f1 binding, whereas AcDNAJB13 weakens it. These findings reveal distinct yet complementary mechanisms by which sHSP and DNAJB13 coordinate with autophagy to restrict viral infection.