Summary: RNA processing and decay pathways have important impacts on RNA viruses, particularly animal‐infecting bunyaviruses, which utilize a cap‐snatching mechanism to translate their mRNAs. However, their effects on plant‐infecting bunyaviruses have not been investigated. The roles of mRNA degradation and non‐sense‐mediated decay components, including DECAPPING 2 (DCP2), EXORIBONUCLEASE 4 (XRN4), ASYMMETRIC LEAVES2 (AS2) and UP‐FRAMESHIFT 1 (UPF1) were investigated in infection of Arabidopsis thaliana by several RNA viruses, including the bunyavirus, tomato spotted wilt virus (TSWV). TSWV infection on mutants with decreased or increased RNA decapping ability resulted in increased and decreased susceptibility, respectively. By contrast, these mutations had the opposite, or no, effect on RNA viruses that use different mRNA capping strategies. Consistent with this, the RNA capping efficiency of TSWV mRNA was higher in a dcp2 mutant. Furthermore, the TSWV N protein partially colocalized with RNA processing body (PB) components and altering decapping activity by heat shock or coinfection with another virus resulted in corresponding changes in TSWV accumulation. The present results indicate that TSWV infection in plants depends on its ability to snatch caps from mRNAs destined for decapping in PBs and that genetic or environmental alteration of RNA processing dynamics can affect infection outcomes.

Although the canonical function of viral coat protein (CP) is to encapsidate the viral genome, they have come to be recognized as multifunctional proteins, involved in almost every stage of the viral infection cycle. However, CP functions of Apple stem pitting virus (ASPV) has not been comprehensively documented. This study aimed to characterize the functions of ASPV CP and any functional diversification caused by sequence diversity of six ASPV CP variants and studied their biological, serological, pathogenic and viral suppressor of RNA silencing (VSR) functions. Six ASPV CP variants that have previously been shown to belong to different subgroups were selected here to study their diversity functions. Agrobacterium mediated infiltration (Agroinfiltration) was used to express YFP-ASPV-CPs in Nicotiana. benthamiana and infect Nicotiana. occidental with PVX-ASPV-CPs in. Confocal microscopy was used to detect YFP-ASPV-CPs florescence. CPs expressed in Escherichia coli BL21 (DE3) were induced by IPTG. In this study, we showed that recombinant CPs expressed in Escherichia coli BL21 (DE3) had different levels of serological reactivity to three anti-ASPV antibodies used to detect ASPV. Furthermore, fusion CPs with YFP (YFP-CPs) expressed in N. benthamiana cells differed in their ability to form aggregates. We also showed that ASPV isolates that harbour these CPs induced different biological symptoms on its herbaceous host N. occidentalis. At the same time, we found that all six CPs when expressed in PVX vector showed similar VSR activity and produced similar symptoms in N. occidentalis, despite their differences in amino acids. Different ASPV isolates induced different symptoms in N. occidentalis, however, ASPV CP variants expressed in PVX vector showed the same symptoms in N. occidentalis plants. Also, we showed that ASPV CP variants has the same level of VSR activity, but they have different abilities to aggregate in N. benthamiana.

We report here the identification of a dsRNA virus, obtained from Fusarium solani strain Newher-7, tentatively named F. solani partitivirus 3 (FsPV3). It consists of four dsRNA segments (dsRNA1–4) with lengths of 1961, 1900, 1830 and 1830 bp, respectively. Sequence analysis showed that dsRNA1 encodes an RNA-dependent RNA polymerase (RdRp), dsRNA2 encodes a capsid protein (CP), dsRNA3 encodes a hypothetical protein of unknown function and dsRNA4 encodes two hypothetical proteins of unknown function. Amino acid sequence comparisons showed that the RdRp of FsPV3 is most similar to that of Hulunbuir Parti tick virus 1. In contrast, the CP of FsPV3, as well as the hypothetical protein encoded by ORF3 of dsRNA3, was most similar to cognate proteins encoded by Colletotrichum-associated partitivirus 2. However, the two hypothetical proteins encoded by dsRNA4 showed no significant similarity to the available sequences in the National Center for Biotechnology Information database and encoded no apparent conserved domains. Phylogenetic analysis of the RdRp and CP showed that FsPV3 clustered together with other species in the genus Alphapartitivirus. Given that proteins encoded by FsPV3 are not sufficiently highly homologous to a single known virus and that it encodes two novel proteins, we suggest that FsPV3 should be regarded as a new member of the genus Alphapartitivirus in the family Partitiviridae. This is the first report of FsPV3 infecting F. solani.

Trifoliate orange (Poncirus trifoliata L) is a thorny tree of the Rue family, which is extensively used as citrus rootstock in China. In January 2021, several leaf yellowing, declining, and wilting...

A major antiviral mechanism in plants is mediated by RNA silencing through the action of DICER-like (DCL) proteins, which cleave dsRNA into discrete small RNA fragments, and ARGONAUTE (AGO) proteins, which use the small RNAs to target single-stranded RNA. RNA silencing can also be amplified through the action of RNA-dependent RNA polymerases (RDRs), which use single stranded RNA to generate dsRNA that in turn is targeted by DCL proteins. As a counter-defense, plant viruses encode viral suppressors of RNA silencing (VSRs) that target different components in the RNA silencing pathway. The tomato Ty-1 gene confers resistance to the DNA virus tomato yellow leaf curl virus (TYLCV) and has been reported to encode an RDRγ protein. However, the molecular mechanisms by which Ty-1 controls TYLCV infection, including whether Ty-1 is involved in RNA silencing, are unknown. Here, by using a transient expression assay, we have confirmed that Ty-1 shows antiviral activity against TYLCV in Nicotiana benthamiana. Also, in transient expression-based silencing assays, Ty-1 augmented systemic transgene silencing in GFP transgenic N. benthamiana plants. Furthermore, co-expression of Ty-1 or other RDRγ proteins from N. benthamiana or Arabidopsis with various proteins resulted in lower protein expression. These results are consistent with a model wherein Ty-1-mediated resistance to TYLCV is due, at least in part, to an increase in RNA silencing activity.