Antek Skotnicki

A tobamovirus of a green alga

Abstract A virus of the green alga Chara corallina has been found and its rod-shaped particles purified and characterized. These particles closely resemble those of tobacco mosaic virus and are serologically related to particles of two tobamoviruses, though they are 532 nm long.

Further studies on Chara corallina virus

Abstract The particles of Chara corallina virus (CCV) and those of tobamoviruses share many properties, but differ in some. CCV particles are tubular, 532 nm long, and 18 nm wide, and are helically constructed with a basic pitch of 2.75 nm; their isoelectric point is pH 3.4–3.7; their sedimentation coefficient (s 20 , w) is 230 S; they contain 5% RNA with a molecular weight of 3.6 × 10 6 daltons, and with a base ratio of G 24.5, A 28.0, C 20.0, U 27.5; their coat protein is similar in size to that of tobamoviruses (about 17.5 × 10 3 daltons). CCV is considered to be a tobamovirus. CCV may be transmitted experimentally to uninfected Chara corallina cells by injection of virus particles, and causes chlorosis and death in about 10–12 days. A classification of CCV and 68 other tobamovirus isolates, whose coat protein composition is known, showed that CCV is distant from all, but is most closely related to the cucurbit tobamoviruses.

In vitro Translation of Polyribosome-Associated RNAs from Tobamovirus-Infected Plants

RNAs associated with polyribosomes in plants infected with the U2 strain of tobacco mosaic virus (TMV) or with sunnhemp mosaic virus have been isolated. Most are about 0.35 X 10(6) daltons in weight. They translate efficiently in vitro to produce their respective coat proteins which were identified by their serological behavior and peptide composition. They also reassemble in vitro with coat protein. The coat protein of sunnhemp mosaic virus reassembles more quickly than that of TMV U2.

Detection of Fiji disease virus in infected sugarcane by nucleic acid hybridization

Clones of Fiji disease virus were obtained by cDNA synthesis from isolated viral genomic double-stranded RNA. Nick-translated probes made from a mixture of clones specifically detected Fiji disease virus in infected sugarcane galls, leaves and growing tips. This method for detection of Fiji disease virus is extremely sensitive, and can be used as a rapid screening procedure for the virus with very small tissue samples.

Mixed infection with two tobamoviruses: the formation of particles containing the coat protein messenger RNAs of either virus.

Plants mixedly infected with the U2 strain of tobacco mosaic virus (T2MV) and sunnhemp mosaic virus (SHMV) and grown at 35 degrees, yield particles of the same modal lengths (300 and 40 nm) as those found in plants singly infected with SHMV, but not in plants infected with T2MV, which yield only the long particles. At least some of the particles produced in mixedly infected plants contain coat proteins of both viruses. When RNAs from these particles are translated in vitro the coat proteins of both viruses are produced, although when a mixture of RNAs from particles of SHMV and T2MV, grown separately, are translated in vitro only SHMV protein is produced. These and other results suggest that the short particles produced in mixedly infected plants contain both coat protein messengers.

Translation in vitro of Artificially Produced Fragments of a Tobamovirus Genome

Particles of the U2 strain of tobacco mosaic virus (TMV) were partly disassembled by SDS, treated with RNases and then phenol, and yielded RNA molecules one quarter to half the size of the intact virus genome. These molecules, when translated in vitro, produced the coat protein of the virus. Reassembly experiments indicated that the active messenger molecules were those that most rapidly reassembled with coat protein; the rate of reassembly was greatly diminished by treatment with spleen phosphodiesterase. Particles of sunnhemp mosaic virus (the bean strain of TMV) resist disassembly by detergent much more than those of the U2 strain of TMV.

Particles produced during a mixed infection by two tobamoviruses contain coat proteins of both viruses.

Particles from plants mixedly infected with two tobamoviruses, whose particles differ in density, were all of a single, intermediate density, suggesting that they contain both coat proteins and that the proteins occur in the same proportion in all particles. Plants inoculated with the genome-containing particles of one of the tobamoviruses together with the noninfective, short, coat protein messenger-containing particles of the other yielded only particles with the density of the first;.there was no evidence of complementation.

On the Nature of the Difference in the Densities of the Particles of Two Tobamoviruses

Particles of sunnhemp mosaic virus (SHMV) are denser than those of the U2 strain of tobacco mosaic virus (T2MV) when their densities are estimated by equilibrium centrifugation in gradients of either cesium chloride or Metrizamide; in cesium chloride the densities are 1.318 and 1.307 g/ml, and in Metrizamide they are 1.249 and 1.240 g/ml. Experiments with particles reassembled from homologous or heterologous mixtures of the RNAs and coat proteins of the viruses show that the difference in their densities is determined by their coat proteins. The disassembled coat proteins of the two viruses have the same density, but polymerized SHMV protein is less dense than polymerized T2MV protein. Particles reassembled from homologous or heterologous mixtures of the RNAs and coat proteins of the viruses have the density of the nucleoprotein particles used as the source of protein. The density difference of the two virus nucleoproteins therefore reflects the different behavior of the two proteins on assembly with RNA.

Abstracts Of Contributed Papers — National Plant Pathology Conference, Sydney, May 1974

Effect of Soil Moisture on Decline of Pinus radiata