VIEW ARTICLE

Physiology and Biochemistry

The Effect of pH and Some Selected Chemicals on the Temperature-Reversible Aggregation of Carnation Ringspot Virus. J. H. Tremaine, Research scientist, Research Station, Agriculture Canada, 6660 N. W. Marine Drive, Vancouver, B.C., Canada, V6T 1X2; W. P. Ronald, technician, Research Station, Agriculture Canada, 6660 N.W. Marine Drive, Vancouver, B.C., Canada, V6T 1X2. Phytopathology 75:467-471. Accepted for publication 6 October 1984. Copyright 1985. Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-75-467.

Two strains of carnation ringspot virus, CRSV-R and CRSV-N aggregate and disaggregate in a temperature-reversible manner. The temperature of solutions of these viruses (0.8 mg/ml) was raised from 25 C to 60- 80 C at a constant rate of 0.25 C/min while the absorbance at 340 nm was recorded. Then the temperature was lowered to 25 C and denaturation was monitored by observing precipitation and testing serological activity by gel diffusion. The aggregation temperature in 0.1 M tris acetate buffers in the pH 4.0 to 8.0 range was lowest at pH 5.0 for CRSV-R (50 C) and at pH 6.0 for CRSV-N (51 C). The effects of increasing concentrations of chemicals were studied with CRSV-R at pH 5.0 and 7.0. The greatest reductions in aggregation temperature without denaturation occurred with 100 mM EDTA (12 C at pH 5.0 and 24 C at pH 7.0) and with 100 mM ethyleneglycol-bis-(β -amino-ethyl ether)-N,N', N'-tetraacetic acid (EGTA) (8 C at pH 5.0 and 16 C at pH 7.0). Sucrose, at 1,000 mM, raised the aggregation temperature into the 70- 80 C range, but virus denaturation occurred at these temperatures in the presence or absence of sucrose. Denaturation occurred at 50- 60 C with KCNS, acetamide, thiourea, and guanidine at pH 7.0 and with guanidine and uranyl acetate at pH 5.0. Small decreases in aggregation temperature without denaturation occurred with increasing concentrations of NaCl, acetamide, urea, Triton X-100, Tween-20, and alginic acid. SDS at concentrations ranging from 0.1 to 4 mM at pH 5 had little effect on the aggregation temperature and virus dissociation occurred at higher SDS concentrations.