Studies on the Infection and the Multiplication of Plant Viruses

V. Changes of soluble proteins and iso-enzymes in tobacco leaf infected with cucumber mosaic virus

Abstract

Changes of isozymes and soluble proteins in tobacco leaf inoculated with cucumber mosaic virus (ordinary strain) are reported. Isozymes and soluble proteins from tobacco leaf at the 4th hr's and 5th day's infection were separated by polyacrylamide gel electrophoresis.
These changes were inconspicuous at the 4th hr's infection, but clearly demonstrated at the 5th day. In infected leaf but not in healthy leaf, proteins, having high molecular weight, were separated on 4.75% gel, remaining their origin unsolved. Peroxidase isozymes pattern did not change by infection, but a few bands of them were activated by the prolonged times of infection. The same tendency was observed by ageing in healthy control leaf. Similar results were obtained in polyphenoloxidase. Total activities of peroxidase and polyphenoloxidase in infected leaf were higher than those in the control. The number of glutamate dehydrogenase isozymes and isocitrate and isocitrate dehydrogenase isozymes decreased by infection. However, activities of glutamate dehydrogenase isozymes in infected leaf were higher than those in the control, and this tendency was reversed in the case of isocitrate dehydrogenase isozymes. Generally, activities of glucose-6-phosphate dehydrogenase isozymes became weak at the 5th day's infection, although some bands showed stronger reaction in infected leaf than in the control. 6-Phosphogluconate dehydrogenase isozymes showed the same tendency as glucose-6-phosphate dehydrogenase isozymes, nevertheless a new band appeared both in infected and control leaf by ageing. The number of acid phosphatase isozymes decreased by infection, but their activities in infected leaf were slightly higher than in the control. Malate dehydrogenase isozymes pattern did not change, but their activities lowered by infection. In infected leaf one band of them remained comparatively high activity even at the 5th day.
These results seem to indicate that changes of the isozymes herein reported are caused by the abnormally physiological state of host plants, including ageing, which may be induced by infection.