- Volume 54, Issue 1, 1981

After infection of Sac(-) cells with the murine coronavirus JHM the synthesis of seven major and two minor RNA species was induced. These RNAs were polyadenylated and single-stranded. Their mol. wt. were estimated by electrophoresis in agarose gels containing methylmercury hydroxide. The values for the major species were 6.67 × 106 for RNA of genome size (RNA 1), 3.42 × 106 for RNA 2, 2.76 × 106 for RNA 3, 1.35 × 106 for RNA 4, 1.19 × 106 for RNA 5, 0.93 × 106 for RNA 6 and 0.62 × 106 for RNA 7. The minor species have a size of 4.7 × 106 (RNA a) and 1.5 × 106 (RNA b). The same number of species were found by electrophoresis after denaturation with glyoxal-dimethyl sulphoxide. No gross difference in number of RNAs and the amount of each species was found between total cytoplasmic RNA, polyadenylated cytoplasmic RNA and RNA extracted from pelleted polysomes.

Plantain virus X (PIVX), a previously undescribed potexvirus, is common in Plantago lanceolata in Great Britain. PIVX infected 22 species from six families, out of 48 species from 10 families tested. Nicotiana × edwardsonii was a useful diagnostic host, although no suitable host is known for lesion assays. Sap from infected N. clevelandii was infective after 10 min at 60 °C, but not 70 °C. Infectivity in dried leaf material of N. × edwardsonii was retained for at least 26 months, and a purified preparation was infective after freezing for at least 3 months.

In negatively stained preparations PIVX has flexuous particles of 570 to 580 by about 12 nm, with clearly visible cross-banding. The pitch of the particles was 3.4 nm, with a true repeat of five turns and probably 8 subunits per turn.

Purification of PIVX from N. clevelandii leaves yielded up to about 30 mg pure unaggregated virus/kg of leaf. Purified virus sedimented as a single component with a sedimentation coefficient ( ) of 119S. The buoyant density in CsCl was 1.31 g/ml, and in Cs2SO4 was 1.259 g/ml. Purified virus contained a single coat protein species which did not migrate anomalously in SDS-polyacrylamide gel electrophoresis, and had an apparent mol. wt. of 28858 to 26000 depending on the method of analysis. PIVX coat protein migrated more slowly in slab-gel electrophoresis than did the coat proteins of six other potexviruses. A single nucleic acid species of about 2.1 × 106 mol. wt. was detected by polyacrylamide gel electrophoresis. No serological relationship to PIVX was detected in tests with the coat proteins of six, and the antisera to seven, other potexviruses. All of the properties described are consistent with PIVX being a distinct member of the potexvirus group.