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Cytology and Histology

Ultrastructure of Extracted Carnation Etched Ring Virus Inclusion Bodies Treated with Proteolytic Enzymes and DNase. R. H. Lawson, Agricultural Research Service, U.S. Dept. of Agriculture, Beltsville, MD 20705; S. S. Hearon, Agricultural Research Service, U.S. Dept. of Agriculture, Beltsville, MD 20705. Phytopathology 67:1217-1226. Accepted for publication 1 May 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1217.

Carnation etched ring virus (CERV) inclusion bodies were extracted from infected leaves of Saponaria vaccaria ‘Pink Beauty’ and treated with proteolytic enzymes. The effect of the enzymes on inclusions in ultrathin sections was compared to the alteration produced in the ultrastructure of inclusions that were exposed to enzymes and subsequently fixed and embedded. Ultrathin sections of extracted inclusions embedded in glycol methacrylate (GMA) were more susceptible to Protease VIII and trypsin when fixed in formalin than in glutaraldehyde or acrolein. Enzymatic treatment removed the matrix before digesting the virions. The time required for digestion decreased as the concentrations of the enzymes increased. Formalin-fixed inclusions embedded in GMA were unaltered after treatment with deoxyribonuclease. Pelleted inclusions and inclusions in suspension that were treated with protease and then fixed in glutaraldehyde and embedded in Epon showed digestion of the matrix before the virions were morphologically altered. Protease digestion occurred more uniformly and rapidly with suspended inclusions than with those that had been pelleted prior to treatment. The greater susceptibility of the inclusion matrix to proteolytic enzyme digestion compared to the virions may indicate a difference in the proteins of the matrix and virions.