Multiple domains of the tobacco mosaic virus p126 protein can independently suppress local and systemic RNA silencing.
Small RNA-mediated RNA silencing is a widespread antiviral mechanism in plants and other organisms. Many viruses encode suppressors of RNA silencing for counter-defense. The p126 protein encoded by Tobacco mosaic virus (TMV) has been reported to be a suppressor of RNA silencing but the mechanism of its function remains unclear. This protein is unique among the known plant viral silencing suppressors because of its large size and multiple domains. Here, we report that the methyltransferase, helicase, and nonconserved region II (NONII) of p126 each has silencing-suppressor function. The silencing-suppression activities of methyltransferase and helicase can be uncoupled from their enzyme activities. Specific amino acids in NONII previously shown to be crucial for viral accumulation and symptom development are also crucial for silencing suppression. These results suggest that some viral proteins have evolved to possess modular structural domains that can independently interfere with host silencing, and that this may be an effective mechanism of increasing the robustness of a virus.
Department of Plant Pathology and Microbiology, College of Bioresources and Agriculture, National Taiwan University, Taipei, Taiwan.
Li-Ya
LY
Wang
Shih-Shun
SS
Lin
Ting-Hsuan
TH
Hung
Tsai-Kun
TK
Li
Nai-Chun
NC
Lin
Tang-Long
TL
Shen
D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004252:DNA Mutational Analysis; D005786:Gene Expression Regulation / Q000235:genetics; D049452:Green Fluorescent Proteins; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000821:virology*; D018515:Plant Leaves / Q000821:virology; D017434:Protein Structure, Tertiary; D034622:RNA Interference / Q000276:immunology; D014026:Nicotiana / Q000235:genetics / Q000821:virology*; D014027:Tobacco Mosaic Virus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
C071899:130k protein, Tobacco mosaic virus; D014764:Viral Proteins; D049452:Green Fluorescent Proteins; D008780:Methyltransferases; D004265:DNA Helicases