P25 and P37 proteins encoded by firespike leafroll-associated virus are viral suppressors of RNA silencing

Abstract

Firespike leafroll-associated virus (FLRaV) is a major pathogen associated with firespike (Odontonema tubaeforme) leafroll disease. Phylogenetic analysis showed that FLRaV possesses typical traits of subgroup II members of ampeloviruses, but encodes two additional proteins, P25 and P37. Here, we determined the microfilament localization of P25 protein. Posttranscriptional gene silencing (PTGS) assay showed that both FLRaV P25 and P37 were able to suppress the local and systemic PTGS and FLRaV P25 was capable of suppressing the green fluorescent protein (GFP) gene silencing triggered by both sense RNA-induced PTGS (S-PTGS) and inverted repeat RNA-induced PTGS (IR-PTGS). In contrast, FLRaV P37 was only able to inhibit the GFP silencing triggered by the S-PTGS but not the IR-PTGS. In the transcriptional gene silencing (TGS) assay, only FLRaV P25 was found to be able to reverse established TGS-mediated silencing of GFP in 16-TGS plants. We also found that FLRaV P25 could aggravate the disease symptom and viral titer of potato virus X in N. benthamiana. These results suggest that FLRaV P25 and P37 may have crucial roles in overcoming host RNA silencing, which provides key insights into our understanding of the molecular mechanisms underlying FLRaV infection.

Identification of RNA silencing suppressor encoded by citrus chlorotic dwarf-associated virus

“…In this study, the potential RSS abilities of six proteins encoded by CCDaV were screened by co-agroinfiltration with pART27-eGFP in 16c plants; CCDaV-V2 exhibited the ability to suppress local and systemic RNA silencing. V2 could not suppress intercellular movement of RNA silencing, indicating that the ability of V2 to suppress PTGS is not through direct binding of siRNAs ( Wang et al, 2022 ). Some studies also showed that V2 encoded by MMDaV, along with p25 and p37 encoded by firespike leafroll-associated virus (FLRaV), could suppress local RNA silencing and long-distance movement of the silencing signal in 16c plants, while not affecting short-distance movement of the silencing signal ( Yang et al, 2018 ; Wang et al, 2022 ).…”

“…V2 could not suppress intercellular movement of RNA silencing, indicating that the ability of V2 to suppress PTGS is not through direct binding of siRNAs ( Wang et al, 2022 ). Some studies also showed that V2 encoded by MMDaV, along with p25 and p37 encoded by firespike leafroll-associated virus (FLRaV), could suppress local RNA silencing and long-distance movement of the silencing signal in 16c plants, while not affecting short-distance movement of the silencing signal ( Yang et al, 2018 ; Wang et al, 2022 ). These results are similar to the results of the present study, and this finding enriches our understanding of the functions of proteins encoded by geminiviruses.…”

Identification and Molecular Characterization of a Novel Carlavirus Infecting Chrysanthemum morifolium in China

“…After confirmation by sequencing, the constructed plasmids and empty vector were individually transferred into the Agrobacterium tumefaciens strain GV3101 by electroporation, as described previously [47,48]. The Agrobacteriummediated inoculation of N. benthamiana was performed as described previously [49,50]. Simultaneously, the PVX-based vector expressing a green fluorescent protein (GFP) (PVX:GFP) was used as a vector control.…”

“…Further amino acid sequence alignment of CRPs showed that CiCV1-CN CRP had a conserved Carlavirus nucleic acid binding domain (IPR002568, 8-92 aa) (Figure 4b). Furthermore, CiCV1-CN CRP was also predicted to have an arginine-rich NLS motif ( 47 RRRR 50 ) and a ZF motif ( 57 CX2CX12CX4C 78 )…”

A newly isolated cotton-infecting Polerovirus with cryptic pathogenicity encodes a weak suppressor of RNA silencing

“…However, silencing of GFP induced this way can be suppressed by the simultaneous expression of VSRs (Voinnet et al, 1999). This method has been used to identify VSRs among virus-encoded proteins for decades (Brigneti et al, 1998;Voinnet et al, 1999;Qu et al, 2003;Cui et al, 2005;Li et al, 2014;Dong et al, 2016;Sinha et al, 2021;Wang et al, 2022). Green fluorescence was observed under a long wavelength (365 nm) using a hand-held UV lamp raised 6 inches above the plants at four days post infiltration (dpi) in the dark room.…”