title: Cucumber mosaic virus suppressor 2b binds to AGO4-related small RNAs and impairs AGO4 activities.
abstract: Cucumber mosaic virus suppressor 2b (CMV2b) is a nuclear viral suppressor that interferes with local and systemic silencing and inhibits AGO1 slicer activity. CMV2b-mediated transgene hypomethylation and its localization in Cajal bodies suggests a role of CMV2b in RNA-directed DNA methylation (RdDM). However, its direct involvement in RdDM, or its binding with small RNAs (sRNAs) in vivo is not yet established. Here, we show that CMV2b binds both microRNAs (miRNAs) and small interfering RNAs (siRNAs) in vivo. sRNA sequencing data from the CMV2b immunocomplex revealed its preferential binding with 24-nt repeat-associated siRNAs. We provide evidence that CMV2b also has direct interaction with the AGO4 protein by recognizing its PAZ and PIWI domains. Subsequent analysis of AGO4 functions revealed that CMV2b reduced AGO4 slicer activity and the methylation of several loci, accompanied by the augmented accumulation of 24-nt siRNAs in Arabidopsis inflorescences. Intriguingly, CMV2b also regulated an AGO4-related epiallele independently of its catalytic potential, which further reinforces the repressive effects of CMV2b on AGO4 activity. Collectively, our results demonstrate that CMV2b can counteract AGO4-related functions. We propose that by adopting novel counter-host defense strategies against AGO1 and AGO4 proteins, CMV creates a favorable cellular niche for its proliferation.
authors: State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors: Sadia
authors: S
authors: Hamera
authors: Xiaoguang
authors: X
authors: Song
authors: Lei
authors: L
authors: Su
authors: Xiaoying
authors: X
authors: Chen
authors: Rongxiang
authors: R
authors: Fang
mesh_terms: D000241:Adenosine / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism / Q000821:virology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D060565:Argonaute Proteins / Q000378:metabolism*; D017799:Cucumovirus / Q000502:physiology*; D019175:DNA Methylation; D054884:Host-Pathogen Interactions; D035683:MicroRNAs / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000821:virology; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C471209:AGO4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D035683:MicroRNAs; D034741:RNA, Small Interfering; D014764:Viral Proteins; D000241:Adenosine