Properties of the products of UTP incorporation by cell-free extracts of leaves infected with bromegrass mosaic virus or with broadbean mottle virus

Abstract

After deproteinization with phenol and detergent, the product of UTP- 3H incorporation by a particulate fraction prepared from barley leaves infected with bromegrass mosaic virus displayed properties consistent with those of a double-stranded RNA. The major part of the label incorporated in the product was resistant to pancreatic ribonuclease (RNase) (5 μg/ml) in 1 × SSC, but was made acid-soluble by treatment with RNase in 0.1 × SSC. Similar results were obtained with the deproteinized product of UTP- 3H incorporation by extracts from broadbean leaves infected with broadbean mottle virus. When the deproteinized product synthesized by extracts from bromegrass mosaic virus-infected leaves was heated in 1 × SSC at increasing temperatures, a sharp transition from RNase resistance to RNase sensitivity was observed, with a T m of 99–100°. With both bromegrass mosaic virus and broadbean mottle virus, the particle-bound product of UTP- 3H incorporation was double-stranded in its native state, as suggested by RNase resistance in 1 × SSC and RNase sensitivity in 0.05 × SSC, respectively, of the radioactive product associated with the particulate leaf fraction. The native products of UTP- 3H incorporation were sensitive to RNase in 0.05 × SSC without any pretreatment of the leaf extracts.