Daiki Murayama

Purification and electron microscopy of potato leafroll virus.

A procedure for purification of potato leafroll virus (PLRV) from its plant host was improved. An extract from diseased Physalis floridana plants was emulsified with an n-butanol-chloroform mixture. The virus in the aqueous phase was concentrated by centrifugation, the pellet was resuspended in 0.01 M phosphate buffer and subjected to emulsification with fluorocarbon (Daifron S-3). The virus, concentrated by additional centrifugation from the aqueous phase, was fractionated in a sucrose density-gradient column. When the final preparation was suspended in 0.01 M phosphate buffer at pH 6.0 and negatively stained by 2% PTA at pH 5.5, the resulting suspension contained uniform particles 25 mμ in diameter (side by side) and with more or less hexagonal profiles. High infectivity was associated with the zone containing these particles. Preparations obtained from healthy plants and virus-free aphids by the same purification procedure did not contain these particles. Examination of ultrathin sections of the infected P. floridana and Datura stramonium plants by electron microscopy indicated that the virus occurred in some of the phloem cells. When PLRV particles were measured in crystalline array in ultrathin sections the size obtained (23 mμ diameters) agreed approximately with that of the purified virus particles.

ON THE INTERFERENCE OF INACTIVATED PLANT VIRUSES

TMVに紫外線照射および加熱処理を行ない, 感染性および抗原性を調べ, 不活化TMVの活性TMVの感染性に対する干渉作用について実験を行なつた.(1) TMVの感染性は紫外線照射 (64×103μW/cm2) によつて喪失したが, 抗原性をも消失させるにはさらに大量の照射が必要であつた. 活性TMVに多量の照射不活化TMVを混じてN. glutinosaに接種すると生ずる壊死斑点数が減少した. すなわち照射不活化TMVは活性TMVの感染性に干渉し, この干渉作用は照射不活化TMVの量を増加しあるいは濃度を高めるにつれて増大した.(2) 照射不活化TMVを予めN. glutinosaの葉面に接種し, 1日後に活性TMVを接種した場合には照射不活化ウイルスの干渉作用が認められたが, 3日以上の間隔をおいた場合には明かな干渉作用が認められなかつた.(3) 以上の干渉作用はいづれも抗原性を有する照射不活化TMVによつて認められたが抗原性を喪失した不活化TMVでは認められなかつた.(4) 加熱処理ではTMVの感染性と抗原性とはほぼ同時に消失した. 抗原性が認められなかつた90°および95℃., 10分処理の不活化TMVは干渉能を示さなかつたが, 僅かに感染性と抗原性とを有していた85℃., 10分処理TMVではそれが認められた.