Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Functional Analysis Of The P0 Protein Of Sugarcane Yellow Leaf Virus: A Suppressor Of Posttranscriptional Gene Silencing

Henrik H Albert¹ , Tichaona Mangwende^{2, 4} , Ming-Li Wang² , T. Erik Mirkov³

¹  USDA ARS, 99-193 Aiea Hts Dr, Aiea, HI 96701, USA

²  Hawaii Agriculture Research Center, 99-193 Aiea Hts Dr, Aiea, HI 96701, USA

³  Texas A&M University Agricultural Experiment Station, 2415 East Highway 83, Weslaco, TX 78596, USA

⁴  present address Dept of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa

Sugarcane yellow leaf virus (SCYLV), the causal agent of sugarcane yellow leaf syndrome is a member of the family luteoviridae, and has recently been assigned to the genus Polerovirus. SCYLV has six major ORFs, all encoding proteins that are significantly similar to those of known functions in other poleroviruses except for the ORF0. The SCYLV ORF0 encodes a 30 kDa protein that shows little amino acid similarity to the P0 protein of other poleroviruses, which are themselves highly diverse. In three other tested poleroviruses (PLRV, BWYV and CABYV) P0 affects virus accumulation and is also a suppressor of posttranscriptional gene silencing (PTGS). Using agroinfiltration of Nicotiana benthamiana with GFP reporter constructs, P0, and previously characterized viral suppressors of PTGS, we previously showed that P0 of SCYLV is also a suppressor of local PTGS induced by a sense GFP (sGFP) construct. We now report that unlike the P0 of BWYV, PLRV and CABYV the SCYLV P0 effectively suppresses systemic PTGS induced by sGFP but not that induced by an inverted repeat GFP (irGFP) construct. Functional analysis with SCYLV P0 deletion constructs indicates the protein has multiple domains required for full supressor function. Leaf infiltration with SCYLV P0 results in severe necrosis in the infiltrated patch; deletions which abolish suppressor activity also abolish necrosis, suggesting these activities may be linked.