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

Subcellular localization of the Poa semilatent virus cysteine-rich γb protein was studied by using different approaches. In infected tissue, γb was detected mainly in the P30 fraction as monomers, dimers and oligomers. Green fluorescent protein-fused γb was found to localize in punctate bodies in the cytoplasm. Colocalization with marker proteins demonstrated that these bodies represent peroxisomes. Immunoelectron microscopy revealed that γb was localized in the peroxisomal matrix and that localization of γb 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 γb functions are not associated with the protein's localization to peroxisomes. © 2005 SGM.