- Volume 69, Issue 4, 1988

The grey tremor mouse is an autosomal recessive mutant characterized by a phenotype of unusual pigmentation, neurological abnormalities and early death. These mice have a spongiform encephalopathy similar to scrapie and Creutzfeldt-Jakob disease. Although the disease is clearly heritable, the grey tremor mouse spongiform pathology has also been transmitted by inoculation of genetically normal mice with diseased brain homogenates. The possibility that a scrapie-like agent is involved has been proposed. We examined brain homogenates from grey tremor mice, scrapie-affected mice and normal mice for the presence of the mouse scrapie agent protein (MoSp33–37) and its normal cellular homologue. All untreated homogenates contained one or both isoforms of this protein as detected on immunoblots. Grey tremor mouse brain homogenates, when protease-treated, showed no evidence of MoSp33–37. A purification method for MoSp33–37 concentrated it in samples from scrapie-affected mice, but this protein was not detected in grey tremor or normal mice. These results suggest that it is unlikely that the scrapie agent is involved in grey tremor disease.

A head-to-tail dimer of cloned DNA from a Swedish isolate of wheat dwarf virus (WDV) was integrated between the T-DNA border sequences of a broad host range binary vector and transferred into cells of wheat seedlings using an Agrobacterium-mediated delivery system. Two-thirds of the inoculated plants developed a systemic infection. Extracts of infected leaves were shown to contain the virus double-stranded (supercoiled, open circular and linear) and single-stranded DNA forms of unit genome length and the virus capsid polypeptide. The results demonstrate the infectivity of a previously sequenced clone of WDV DNA.

Phaseolus vulgaris ‘Top Crop’ plants inoculated with a mixture of cloned tandem (head to tail) dimers of each component of bean golden mosaic virus (BGMV) developed yellow mosaic symptoms identical to those induced by inoculation with BGMV particles or BGMV ssDNA. Progeny virus particles isolated from plants infected with such cloned DNAs resembled BGMV particles by electron microscopy, reacted with anti-BGMV serum and contained circular unit-length ssDNA. Southern blot analysis of DNA extracted from plants infected with cloned DNA dimers detected virus-specific ssDNA and dsDNA species similar to those found in cells infected following inoculation with BGMV particles.