Localization of Poa semilatent virus cysteine-rich protein in peroxisomes is dispensable for its ability to suppress RNA silencing

1 A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia 2 M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Str., Moscow 117997, Russia 3 Institute of Plant Virology, Microbiology and Biosafety, Federal Biological Research Centre for Agriculture and Forestry, Messeweg 11/12, D-38104 Braunschweig, Germany Correspondence S. Yu. Morozov morozov{at}genebee.msu.su Subcellular localization of the Poa semilatent virus cysteine-rich b protein was studied by using different approaches. In infected tissue, b was detected mainly in the P30 fraction as monomers, dimers and oligomers. Green fluorescent protein-fused b was found to localize in punctate bodies in the cytoplasm. Colocalization with marker proteins demonstrated that these bodies represent peroxisomes. Immunoelectron microscopy revealed that b was localized in the peroxisomal matrix and that localization of b in peroxisomes required the C-terminal signal tripeptide SKL. An SKL-deletion mutant exhibited a diffuse localization, but retained the protein's ability to suppress RNA silencing, determine infection phenotype and support virus systemic spread. These data indicate that b functions are not associated with the protein's localization to peroxisomes.