in vitro. Molecular Plant Pathology On-Line 1997/0123ueda

Molecular Plant Pathology On-Line [http://www.bspp.org.uk/mppol/1997/0123ueda]

The rice dwarf phytoreovirus structural protein P7 possesses non-specific nucleic acids binding activity in vitro

S Ueda, I Uyeda.

Laboratory of Plant Virology and Mycology, Department of Agrobiology and Bioresources, Faculty of Agriculture, Hokkaido University, Sapporo 060, Japan

Corresponding Author:

I Uyeda, Laboratory of Plant Virology and Mycology, Department of Agrobiology and Bioresources, Faculty of Agriculture, Hokkaido University, Sapporo 060, Japan

email: Uyeda@res.agr.hokudai.ac.jp

Accepted: 23 January 1997

Abstract:

Interactions between structural proteins and genomic dsRNAs of purified rice dwarf phytoreovirus (RDV) were analysed by centrifugations in CsCl and cesium trifluoroacetate (CsTFA). In the presence of a high concentration of MgCl2, most of P8 was dissociated from the purified particles and core particles were obtained by ultracentrifugation in histidine-MgCl2 solution. By CsTFA density gradient centrifugation, core particles were separated into open core particles, protein-free genomic dsRNAs, and P7-dsRNA complexes (P7-dsRNA) according to densities. Open core particles were free from genomic dsRNAs. Transcriptional activities in vitro were not detected in open core particles and P7-dsRNA, although open core particles retained about 12% of the activity of purified virus. P7 was tested for nucleic acids binding activity by a Northwestern blotting assay using various nucleic acid probes. Intact P7 possessed activity that binds not only the RDV dsRNA or ssRNA but also rice ragged stunt virus dsRNA and ssRNA, and lambdaDNA fragments. Although CsTFA centrifugation released P7 from the core particles, open core particles still retained some P7. Under the electron microscope, open core particles retained the spike-like structure. Antiserum to P7 failed to react with the surface structure of the open core particles suggesting that it is located inside the particles.

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