Functional Analysis Of The P15 Protein Encoded By Garlic Virus X ORF6

Garlic belongs to the genus Allium in Lilicancene.Under natural circumstances,garlic is infected by a compound of viruses,including potexviruses,carlaviruses and Allexivirus.Garlic virus X(GarVX)is one of the most important pathogens causing garlic virus disease,belonging to the genus Allexivirus.GarVX is a single-stranded positive-sense RNA virus,consisting of 8106 nucleotides and has six open reading frames(Open Reading Frame,ORF),the ORF6 encoded 15 kDa(p15)protein is predicted to be a cysteine-rich protein(CRP).It has been reported that plant-virus-encoded CRPs are the determinants of viral pathogens,and that many CRPs have a silencing suppression activity,but the specific function of p15 is unknown.In this study,to investigate the function of p15 protein encoded by GarVX ORF6,green fluorescent expression vector of p15 protein was constructed and observed underconfocal microscopy.The p15 protein is localized in the periphery,nucleus and nucleolus of cells.Potato virus X(PVX)mediated overexpression of p15 protein(PVX-p15)caused dwarf,malformation of leaves and increased accumulation of PVX compared with PVX-GFP,which suggest that p15 is a viral pathogenic factor of PVX-p15.In addition,by using Agrobacterium infiltration on 16 c plants(GFP transgenic line)and turnip crinkle virus(TCV)movement complementation assay,it is demonstrated that p15 has weak RNA silencing suppression activity.Removal of the nuclear localization signal(NLS)constructed mutant(p15m)did not localize in the nucleus,reducing its pathogenicity,but the ability of RNA silencing suppression is not affected.In summary,the preliminary function of GarVX p15 is investigated in these experiments,and it was clarified that GFP fused p15 was distributed in the cytoplasm,nucleus and nucleolus.Expression of p15 from PVX shows that p15 is a virulence factor for reconstructed PVX-p15.Moreover,it is demonstrated that p15 possesses weak RNA silencing suppressor activity.Removal of an amino acid motif resembling a nuclear localization signal(NLS)prevents p15 from accumulating in the nucleus but do not abolish its silencing suppression activity.Studying the function of GarVX p15 helps to understand the pathogenic mechanism of this genus virus.