Golden Yellow Mosaic Virus Research Articles

Single-stranded DNA genome in a whitefly-transmitted plant virus

Bean golden yellow mosaic virus (GYMV) DNA sedimented in sucrose density gradients and in an analytical ultracentrifuge as a single component. Values of s 20,w which depended upon ionic strength (i) and pH, were 16.0 (pH = 7.0, i = 0.1); 16.3 (pH = 7.0, i = 1.0); 9.0 (pH = 13, i = 0.1); and 12.0 (0.1 N NaOH, i = 1.0). GYMV-DNA banded in CsCl as a single component with a buoyant density of 1.7170 g/ml and exhibited hyperchromicity when heated between 20 and 70°. Hyperchromicity and a shift in the ultraviolet light absorption maximum were observed when the DNA was treated with formaldehyde (1.8%) at room temperature. Nuclease sensitivity tests showed that the DNA was susceptible to hydrolysis by DNase I and nuclease S 1 (specific for single-stranded DNA) but not to hydrolysis by RNase A or by 0.3 N NaOH. Molecular weight values calculated from sedimentation velocity and CsCl equilibrium data were in the range of 0.66 to 0.95 × 10 6 daltons GYMV thus contains DNA with the properties of a predominantly single-stranded molecule and represents the first reported single-stranded DNA virus from plants.

Infectious DNA from a whitefly-transmitted virus of Phaseolus vulgaris

GOLDEN yellow mosaic (bean golden mosaic) is a widespread disease of Phaseolus vulgaris in tropical and subtropical America1. The disease causes serious yield losses in several countries where beans are an important dietary staple2,3. The causal agent, long presumed to be a virus, also infects P. lunatus and Macroptilium lathyroides in the American tropics4,5. The pathogen is transmitted in nature and in the laboratory by the whitefly Bemisia tabaci Genn., and is also mechanically transmissible from the sap of infected plants3,5. An unusually small (18-nm diameter) nucleoprotein particle has been purified from diseased plants5,6, and shown conclusively to be the whitefly-transmitted virus causing the disease5. Electron microscopy of purified virus revealed predominately geminate aggregates of the 18-nm particles5,6. The virus must be aldehyde-fixed before negative staining because it is disruped by the heavy metal salts (ammonium molybdate, sodium phosphotungstate, or uranyl acetate) used as negative stains. Thus, it is not known whether the geminate aggregate is the infectious entity or an artefact of fixation5. Nonetheless, its unusually small size sets this virus apart from most other plant viruses. I describe here the extraction of infectious DNA from purified golden yellow mosaic virus (GYMV), a result that further separates this virus from other previously described plant viruses.