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Another virus trick to counterattack host RNA silencing defense

Date:2014-02-13 Hits:394

In plants, RNA silencing plays a key role in antiviral defense. Accordingly, most, if not all, plant viruses have evolved to encode viral suppressors of RNA silencing that target different steps of RNA silencing pathway to counteract host defense. Recently, a collaborative effort made by Dr.  Li Zhenghe and Dr. Zhou Xueping ’s group in Institute of Biotechnology of CAB has uncovered a novel mechanism by which a plant DNA virus suppresses RNA silencing defense. In this study, Tomato yellow leaf curl China virus (TYLCCNV), a member of Geminiviridae family, was shown to significantly upregulate a host calmodulin-like protein (rgs-CaM), which is a plant endogenous suppressor of RNA silencing. Genetic evidence showed that rgs-CaM is required for TYLCCNV to suppress post-transcriptional gene silencing and to cause robust infection. Further, induction of rgs-CaM suppressed the production of secondary siRNAs, likely through repressing RNA-DEPENDENT RNA POLYMERASE 6 (RDR6) expression. RDR6 was further shown to confer RNA silencing-based defense against and host range restriction on geminivirus infection. These findings thus reveal a distinct mechanism for virus to suppress PTGS through usurpation of a host endogenous suppressor of RNA silencing, and highlight an essential role for RDR6 in RNA silencing defense response against geminivirus infection.
This work was recently published in Feb 06, 2014 online issue of PLoS Pathogens ( This study was supported by grants from the Major Program of National Natural Science Foundation of China (31390422) and China National Science Funds for Excellent Young Scientists (31222004), National Basic Research Program (973) of China (2014CB138400), etc.