Different roles for RNA silencing and RNA processing components in virus recovery and virus-induced gene silencing in plants.
A major antiviral mechanism in plants is mediated by RNA silencing, which relies on the cleavage of viral dsRNA into virus-derived small interfering RNAs (vsiRNAs) by DICER-like enzymes. Members of the Argonaute (AGO) family of endonucleases then use these vsiRNA as guides to target viral RNA. This can result in a phenomenon known as recovery, whereby the plant silences viral gene expression and recovers from viral symptoms. Endogenous mRNAs can also be targeted by vsiRNAs in a phenomenon known as virus-induced gene silencing (VIGS). Although related to other RNA silencing mechanisms, it has not been established if recovery and VIGS are mediated by the same molecular mechanisms. We used tobacco rattle virus (TRV) carrying a fragment of the phytoene desaturase (PDS) gene (TRV-PDS) or expressing green fluorescent protein (TRV-GFP) as readouts for VIGS and recovery, respectively, in Arabidopsis ago mutants. Our results demonstrated roles for AGO2 and AGO4 in susceptibility to TRV, whereas VIGS of endogenous genes appeared to be largely mediated by AGO1. However, recovery appeared to be mediated by different components, as all the aforementioned mutants were able to recover from TRV-GFP inoculation. TRV RNAs from recovered plants associated less with ribosomes, suggesting that recovery involves translational repression of viral transcripts. Translationally repressed RNAs often accumulate in RNA processing bodies (PBs), where they are eventually processed by decapping enzymes. Consistent with this, we found that viral recovery induced increased PB formation and that a decapping mutant (DCP2) showed increased VIGS and virus RNA accumulation, indicating an important role for PBs in eliminating viral RNA.
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada.
Xiaofang
X
Ma
Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada.
Marie-Claude
MC
Nicole
Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada.
Louis-Valentin
LV
Meteignier
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China.
Ni
N
Hong
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China.
Guoping
G
Wang
Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada peter.moffett@usherbrooke.ca.
Peter
P
Moffett
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D060565:Argonaute Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000821:virology; D034622:RNA Interference; D012328:RNA Viruses / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism
D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D034741:RNA, Small Interfering; D012367:RNA, Viral; D049452:Green Fluorescent Proteins; D010088:Oxidoreductases; C022398:phytoene dehydrogenase
Arabidopsis; Argonaute; DCP2; RNA silencing; VIGS; decapping.; tobacco rattle virus