Studies on the movement protein encoded by plant virus genome as a determination factor of host range.

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The present study was undertaken to investigate the movement protein encoded by plant virus genome as a determination factor of host range. Using apple chlorotic leaf spot virus (ACLSV) and apple stem grooving virus (ASGV), following results were obtained.1. A putative movement protin of Mr50kDa encoded by the ORF2 of ACLSV (P-209) genome was expressed in Escherichia coli using an expression vector and wasthern used to produce an antiserum.2. Immunoblot analysis using an antiserum raised against the 50kDa protein showedd that the ORF2 protein of ACLSV was detected in both cell wall and cell membrane fractions prepared from intected Chenopodium quinoatissues.3. The ORF2 protein from infected tissues had a Mr52kDa, larger than that of full-length ORF2 protein (50kDa) expressed in E.coli. Incubation of the 52kDa protein with alkaline phosphatase resulted in a decrease in its apparenet mol. wt. from 52kDa to 50kDa, strongly suggested that the ORF2 protein of ACLSV is phoshorylated in infected plant tissues.4. Immunogold labelling of tissue sections of ACLSV-infected C.quionoaplants showed that the ORF2 protein was found associated with cell wall.5. The amino acid sequence of the ORF2 protein of ACLSV (MO-5), defective strain on long distance movement was determined. The ORF2 protein of MO-5 consistes of 460 amino acis (Mr50.4kDa) and shows 80.8% similarity with that of P-209. Immunoblot analysis indicated that the ORF2 protein was detected in cell wall and soluble fraction prepared from infected C.quinoatissues.6. The amino acid sequence of the movement protein of ASGV (V-3) isolated from Japanese pear was determined. The sequence comparisons of the movement protein among ASGV isolated revealed that the movement proteins were highly conserved among isolated (94.7-99.7%).