Non-structural protein 1 from avian influenza virus H9N2 is an efficient RNA silencing suppressor with characteristics that differ from those of Tomato bushy stunt virus p19
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Non-structural protein 1 (NS1) of influenza A virus is a multifunctional dimeric protein that contains a conserved N-terminal RNA binding domain. Studies have shown that NS1 suppresses RNA silencing and the NS1 proteins encoded by different influenza A virus strains exhibit differential RNA silencing suppression activities. In this study, we showed that the NS1 protein from avian influenza virus (AIV) H9N2 suppressed systemic RNA silencing induced by sense RNA or dsRNA. It resulted in more severe Potato virus X symptom, but could not reverse established systemic green fluorescent protein silencing in Nicotiana benthamiana. In addition, its systemic silencing suppression activity was much weaker than that of p19. The local silencing suppression activity of AIV H9N2 NS1 was most powerful at 7 dpi and was even stronger than that of p19. And the inhibition ability to RNA silencing of NS1 is stronger than that of p19 in human cells. Collectively, these results indicate that AIV H9N2 NS1 is an effective RNA silencing suppressor that likely targets downstream step(s) of dsRNA formation at an early stage in RNA silencing. Although NS1 and p19 both bind siRNA, their suppression mechanisms seem to differ because of differences in their suppression activities at various times post-infiltration and because p19 can reverse established systemic RNA silencing, but NS1 cannot.
KeywordsAvian influenza virus RNA silencing suppressor NS1 H9N2 p19
We thank Prof. David Baulcombe for providing N. benthamiana 16c seeds and the p19 gene and Prof. Zhizhong Cui for providing the avian influenza virus H9N2 strain. And thanks are due to Dr. Zizhang Zhou and Dr. Haifang Li for the assistance in animal experiments. This work was supported by grants from the Natural Science Foundation of Shandong Province [ZR2015CM018] and National Natural Science Foundation of China [31272113 and 31300730].
RY and XJ performed the main experiments and edited the paper; CZ participated in experimental design; JX, WL, YX, and LG were involved in executing the study; HL guided the execution of the study and revised the paper.
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Conflict of interest
The authors declare no conflict of interest.
Human and animal consent
The research described in the paper does not use any human or animal subjects.