Amino acid sequence motifs essential for P0-mediated suppression of RNA silencing in an isolate of potato leafroll virus from Inner Mongolia.
Polerovirus P0 suppressors of host gene silencing contain a consensus F-box-like motif with Leu/Pro (L/P) requirements for suppressor activity. The Inner Mongolian Potato leafroll virus (PLRV) P0 protein (P0(PL-IM)) has an unusual F-box-like motif that contains a Trp/Gly (W/G) sequence and an additional GW/WG-like motif (G139/W140/G141) that is lacking in other P0 proteins. We used Agrobacterium infiltration-mediated RNA silencing assays to establish that P0(PL-IM) has a strong suppressor activity. Mutagenesis experiments demonstrated that the P0(PL-IM) F-box-like motif encompasses amino acids 76-LPRHLHYECLEWGLLCG THP-95, and that the suppressor activity is abolished by L76A, W87A, or G88A substitution. The suppressor activity is also weakened substantially by mutations within the G139/W140/G141 region and is eliminated by a mutation (F220R) in a C-terminal conserved sequence of P0(PL-IM). As has been observed with other P0 proteins, P0(PL-IM) suppression is correlated with reduced accumulation of the host AGO1-silencing complex protein. However, P0(PL-IM) fails to bind SKP1, which functions in a proteasome pathway that may be involved in AGO1 degradation. These results suggest that P0(PL-IM) may suppress RNA silencing by using an alternative pathway to target AGO1 for degradation. Our results help improve our understanding of the molecular mechanisms involved in PLRV infection.
Tao
T
Zhuo
Yuan-Yuan
YY
Li
Hai-Ying
HY
Xiang
Zhan-Yu
ZY
Wu
Xian-Bin
XB
Wang
Ying
Y
Wang
Yong-Liang
YL
Zhang
Da-Wei
DW
Li
Jia-Lin
JL
Yu
Cheng-Gui
CG
Han
D000595:Amino Acid Sequence; D060565:Argonaute Proteins; D002681:China; D017124:Conserved Sequence; D044782:F-Box Motifs; D018506:Gene Expression Regulation, Plant; D052679:Luteoviridae / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000821:virology*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000821:virology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism*; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D011198:Solanum tuberosum / Q000821:virology*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
D060565:Argonaute Proteins; D010940:Plant Proteins; D034741:RNA, Small Interfering; D044786:S-Phase Kinase-Associated Proteins; D014764:Viral Proteins