A persistent amalgavirus suppresses jasmonate-mediated defense and increases susceptibility of pepper to tobamovirus infection

This is the authors' abstract. We don't add key points for this paper.

Chili pepper ( Capsicum annuum L.) is an economically important crop in China but its production is increasingly threatened by viral diseases. In this study, Capsicum annuum amalgavirus 1 (CaAV1), a seed-transmitted and asymptomatic virus previously reported in the United States, was identified in Dezhou and Linyi cities, Shandong Province, China, through transcriptome sequencing followed by RT-PCR validation. Seeds collected from CaAV1-positive field plants showed a virus detection rate of 63% (26/41). When these seeds were sown, 59% (49/83) of the resulting progeny plants tested positive for CaAV1 in leaf tissues, indicating a high rate of seed-associated transmission. Although CaAV1 infection did not cause visible phenotypic changes, transcriptome analysis revealed significant downregulation of genes associated with jasmonate (JA) signaling, which was consistent with metabolomic data showing reduced endogenous JA levels. Because JA plays a central role in antiviral defense, we hypothesized that this JA-compromised state may facilitate infection by other viruses. Indeed, co-infection assays with tomato brown rugose fruit virus (ToBRFV; Tobamovirus fructirugosum ) and pepper mild mottle virus (PMMoV; Tobamovirus capsici ) showed that CaAV1+ plants had significantly higher viral RNA accumulation, elevated coat protein levels, and more severe disease symptoms compared with controls. These results indicate that CaAV1 establishes an asymptomatic yet biologically active infection that suppresses JA and enhances host susceptibility to secondary viral infection.