Soluble Antigens from Barley Leaves Infected with Barley Stripe Mosaic Virus

Soluble leaf proteins from barley plants (Hordeum vulgare L., var. Yokozuna) infected with barley stripe mosaic virus (BSMV) were separated electrophoretically in 5% polyacrylamide gel. After infection, fresh weight and fraction I protein in chloroplasts of infected leaves decreased considerably in comparison with healthy controls. After symptom appearance, new bands appeared in the gel column which migrated more slowly than fraction I protein. They were characterized as soluble antigens, because of their positive reaction with BSMV antiserum and their nonsedimentable character upon ultracentrifugation. Co-electrophoresis of the soluble antigens and BSMV protein suggested that the soluble antigens were various aggregates of viral protein.The soluble antigens were detected not only from the inoculated leaves (leaf one) but also from systemically infected leaves (leaf two). During symptom development, the amount of the soluble antigens in leaf two continued to increase, but in leaf one it reached a maximum 4 days after inoculation and then decreased. Possible role of the soluble antigens in virus synthesis is discussed.