Plantain Virus X: a New Potexvirus from Plantago lanceolata

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Abstract
Plantain virus X (PlVX), a previously undescribed potexvirus, is common in P. lanceolata in Great Britain [UK]. PlVX infected 22 spp. from 6 families, out of 48 spp. from 10 families tested. Nicotiana .times. 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.degree. C but not 70.degree. C. Infectivity in dried leaf material of N. .times. edwardsonii was retained for at least 26 mo. and a purified preparation was infective after freezing for at least 3 mo. In negatively stained preparations PlVX has flexuous particles of 570-580 by about 12 nm, with clearly visible cross-banding. The pitch of the particles was 3.4 nm, with a true repeat of 5 turns and probably 8 4/5 subunits/turn. Purification of PlVX 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[sodium dodecyl sulfate]-polyacrylamide gel electrophoresis, and had an apparent MW of 28,858-26,000 depending on the method of analysis. PlVX coat protein migrated more slowly in slab-gel electrophoresis than did the coat proteins of 6 other potexviruses. A single nucleic acid species of about 2.1 .times. 106 MW was detected by polyacrylamide gel electrophoresis. No serological relationship to PlVX was detected in tests with the coat proteins of 6, and the antisera to 7, other potexviruses. All of the properties described are consistent with PlVX being a distinct member of the potexvirus group.