Ethylene plays critical roles in plant development and biotic stress response, but the mechanism of ethylene in host antiviral response remains unclear. Here, we report that Rice dwarf virus (RDV) triggers ethylene production by stimulating the activity of S-adenosyl-L-methionine synthetase (SAMS), a key component of the ethylene synthesis pathway, resulting in elevated susceptibility to RDV. RDV-encoded Pns11 protein specifically interacted with OsSAMS1 to enhance its enzymatic activity, leading to higher ethylene levels in both RDV-infected and Pns11-overexpressing rice. Consistent with a counter-defense role for ethylene, Pns11-overexpressing rice, as well as those overexpressing OsSAMS1, were substantially more susceptible to RDV infection, and a similar effect was observed in rice plants treated with an ethylene precursor. Conversely, OsSAMS1-knockout mutants, as well as an osein2 mutant defective in ethylene signaling, resisted RDV infection more robustly. Our findings uncover a novel mechanism which RDV manipulates ethylene biosynthesis in the host plants to achieve efficient infection.

RNA silencing has evolved as a widespread antiviral strategy in many eukaryotic organisms. Antiviral RNA silencing is mediated by virus-derived small RNAs (vsiRNAs), created by the cleavage of double-stranded viral RNA substrates by Dicer (Dcr) in animals or Dicer-like (DCL) proteins in plants. However, little is known about how the RNA silencing mechanisms of different hosts respond to the same virus infection. We performed high-throughput small RNA sequencing in Nephotettix cincticeps and Oryza sativa infected with Rice dwarf phytoreovirus and analyzed the distinct accumulation of vsiRNAs in these two hosts. The results suggested a potential branch in the evolution of antiviral RNA silencing of insect and plant hosts. The rice vsiRNAs were predominantly 21 and 22 nucleotides (nt) long, suggesting that OsDCL4 and OsDCL2 are involved in their production, whereas 21-nt vsiRNAs dominated in leafhopper, suggesting the involvement of a Dcr-2 homolog. Furthermore, we identified ~50-fold more vsiRNAs in rice than in leafhoppers, which might be partially attributable to the activity of RNA-dependent RNA polymerase 6 (RDR6) in rice and the lack of RDR genes in leafhoppers. Our data established a basis for further comparative studies on the evolution of RNA silencing-based interactions between a virus and its hosts, across kingdoms.

Therapeutic Human papillomavirus (HPVs) vaccines are designed to enhance the immunogenicity of HPV and promote the elimination of tumor cells effectively. Mounting evidence implies that tumor-resident microbiomes may influence therapeutic outcomes through immune modulation. In this study, we evaluated whether the intratumoral microbiota affects the efficacy of the therapeutic HPV vaccine. We analyzed RNA sequencing data from tumor tissues of C57BL/6N female mice treated with a DNA vaccine incorporating HPV16 E6/E7 antigens fused with the chemokine CCL11. Microbial community data were acquired using the PathSeq bioinformatics pipeline. Alpha diversity was estimated using the Shannon index and the number of observed taxonomic features, while beta diversity was assessed via principal coordinate analysis (PCoA) based on Bray–Curtis distance. Linear discriminant analysis Effect Size (LEfSe) analysis was performed to identify differentially abundant microbial taxa. Immune cell infiltration was characterized using the xCell deconvolution method. The analysis revealed significant divergence in both the alpha- and beta-diversity metrics of intratumoral microbiota, associated with treatment responsiveness. Vaccinated groups exhibited enriched abundances of the phyla Proteobacteria, together with a concomitant reduction in Firmicutes and Actinobacteria, and were associated with a positive response to cancer immunotherapy. Additionally, intratumoral microbiome composition and diversity correlated with the increased infiltration of CD8⁺ T cells, natural killer T (NKT) cells, and myeloid cells. This study identifies intratumoral microbiota remodeling as a key feature of therapeutic HPV vaccine response. The observed coordination between bacterial signatures and immune cell infiltration is associative and raises the hypothesis that intratumoral bacteria may modulate, rather than drive, antitumor immunity. These findings support the development of intratumoral microbiota profiling and highlight the potential for microbiota-targeted strategies to enhance cancer immunotherapy efficacy.