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Index >>Plant Viruses >> Bromovirus Group - Brome Mosaic Virus (BMV)

Bromovirus Group - Brome Mosaic Virus (BMV)

	Bromovirus Group - Brome Mosaic Virus (BMV) -The bromoviruses do not show appreciable heterogeneity on sucrose density gradient centrifugation. They, however, show heterogeneity when subjected to bouyant density centrifugation in CsCl solutions. The heterogeneity is associated with differences in nucleic acid content. Brome mosaic virus (BMV) Density gradient centrifugation does not show the multiparticulate nature of BMV. Four different RNA species have, however, been differentiated by their differences in bouyant densities in CsCl. RNA-1 (MW 1.5 x 106 daltons) is contained by the most dense particle. It contains the gene for temperature sensitivity and lesion formation.
RNA-2 CMW 1.0 x 106 daIt9ns) is contained by the least dense particle. Control of local and primary lesion alterations is located either on RNA-2 or RNA-3. RNA-3 (MW .0.85 x 106 daltons) contains the, cistron for capsid protein, plus a cistron for a second protein. RNA-4 (MW 0.32 X 106 daltons) is a monocistronic, messenger for capsid protein, but probably lacks the gene for replicase or a replicase recognition site. Elimination of anyone type reduces infectivity to a low level. RNA-4, although encapsidated, is not required for infectivity. Its elimination does not result in reduction of infectivity. Its genetic information is also contained in RNA-3. RNA-4 is probably not replicated, but may be formed as a specific nuclease product or component 3.
BMV, CCMY and BBMV are physically and/or genetically related small icosahedral viruses. The particles sediment at 4.1-4.8 106 daltons and contain 21-24% RNA. The protein shell is composed of 18R coat protein molecules clustered into 32 morphological units of 20 hexameres and 12 pentameres with T = 3. RNAs-1 to 3 are required to initiate BMV or CCMV infections. BBMV appears to require only RNA-l and RNA-2. Bancroft (1972) has obtained hybrid viruses from BMV RNA-l and 2 plus CCMV RNA-3. These hybrids possess some of the properties of both viruses. CCMV normally infects cowpea but not barley. BMV infects barley but not cowpea. The hybrid virus infects neither. It is restricted 10 hosts common to both viruses.

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