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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #363887
Research Project: Improved Winter Wheat Disease Resistance and Quality through Molecular Biology, Genetics, and Breeding

Location: Wheat, Sorghum and Forage Research

Title: P1 binds to dsRNAs without size and sequence specificity and a GW motif is crucial for suppression of RNA silencing

Author
item GUPTA, ADARSH - University Of Nebraska
item Tatineni, Satyanarayana - Ts

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2019
Publication Date: 5/24/2019
Publication URL: https://handle.nal.usda.gov/10113/6530005
Citation: Gupta, A.K., Tatineni, S. 2019. P1 binds to dsRNAs without size and sequence specificity and a GW motif is crucial for suppression of RNA silencing. Viruses. 11(5):472. https://doi.org/10.3390/v11050472.
DOI: https://doi.org/10.3390/v11050472

Interpretive Summary: Wheat streak mosaic virus (WSMV) is the most economically important virus infecting wheat in the Great Plains USA. Virus-encoded suppressors of RNA silencing play a pivotal role in combating the host defense systems. Studying suppressors of RNA silencing and unraveling their molecular mechanisms are important not only to understand their diversity, regulation and evolution but also to develop and fine-tune approaches for developing new disease management approaches. WSMV suppresses RNA silencing with the P1 protein to combat host defense mechanisms. This research found that the P1 protein suppresses the host RNA silencing at multiple levels by protecting virus-specific RNAs from degradation. The WSMV P1 protein can be used to unravel the mechanisms of host RNA silencing in wheat, and provide a novel route to attain consistent high-level expression since many biotechnological applications are impaired by the host RNA silencing.

Technical Abstract: Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae) is an economically important virus infecting wheat in the Great Plains region of the USA. Previously, we reported that the P1 protein of WSMV acts as a viral suppressor of RNA silencing. In this study, we delineated the minimal region of WSMV P1 and examined its mechanisms in suppression of RNA silencing. We found that the 25 N-terminal amino acids are dispensable, while deletion of a single amino acid at the C-terminal region completely abolished the RNA silencing suppression activity of P1. Electrophoretic mobility shift assays with in vitro expressed P1 revealed that the P1 protein formed complexes with green fluorescent protein-derived 180-nt dsRNA and 21 and 24-nt ds-siRNAs, and WSMV coat protein-specific 600-nt dsRNA. These data suggest that the P1 protein of WSMV binds to dsRNAs in a size- and sequence-independent manner. Additionally, in vitro dicing assay with human Dicer revealed that the P1 protein efficiently protects dsRNAs from processing by Dicer into siRNAs, by forming complexes with dsRNA. Sequence comparison of P1-like proteins from select potyvirid species reveled that WSMV P1 harbors a GW motif in a domain that could be involved in Argonaute-binding at the C-terminal region. Disruption of GW motif in WSMV P1 through W303A mutation resulted in loss of silencing suppression function and enhancement of pathogenicity, and abolished WSMV viability. These data suggest that the mechanisms of suppression of RNA silencing of P1 proteins of potyvirid species appear to be broadly conserved in the family Potyviridae.