A study of tubes produced in plants infected with a strain of turnip yellow mosaic virus.

Abstract

Abstract Electron microscopic examination of crude specimens made from plants infected with a necrotic strain of turnip yellow mosaic virus showed that infection led to the production of tubes as well as virus particles. These tubes, which usually appeared to occur in coaxial groups, were between 110 and 250 mμ wide and up to several microns long. With the aid of magnesium bentonite and differential centrifugation, almost pure preparations of the tubes could be made from the sap of infected plants. Such preparations contained mainly protein and were serologically related to the virus. Optical diffractometry and photographic integration techniques applied to electron micrographs of the tubes, revealed that they were made up of hexagonally packed, hexagonal rosettes, comparable in size to the hexamer morphological subunits of the virus. Strong evidence of a clockwise skew on the rosettes was obtained. The orientation of the hexagonal lattice was not the same on all tubes, but the variation was limited, the short axes of the hexagons comprising the lattice always lying within 15 degrees of the tube axis. Moreover, optical diffractometry of shadowed carbon replicas of the tubes revealed that in all but a small minority, the long-running rows of hexagons of the lattice formed right-handed helices. Cones, structurally related to the tubes, were occasionally found. There was no evidence that tubes were produced in plants infected with three other strains of turnip yellow mosaic virus, but a small number of tubes about 55 mμ in width were seen in specimens made from pumpkins infected with wild cucumber mosaic virus.