VIEW ARTICLE

Etiology

Identification of Single- and Double-Stranded RNAs Associated with Maize Stripe Virus. B. W. Falk, University of Florida, Agricultural Research and Education Center, Belle Glade 33430; J. H. Tsai, University of Florida, Agricultural Research and Education Center, Fort Lauderdale 33314. Phytopathology 74:909-915. Accepted for publication 29 February 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-909.

Purified nucleoprotein from maize stripe virus (MStpV)-infected plants formed a single band with a density of 1.27 g/cc in cesium sulfate equilibrium density gradients, but sedimented in rate-zonal sucrose density gradients as four major nucleoprotein components with sedimentation coefficients between ~70 and 187 S. The purified nucleoproteins from both the cesium sulfate and sucrose gradients were infectious. A complex mixture of both single- and double-stranded (ss- and ds-, respectively) RNAs was identified in all purified nucleoprotein preparations of MStpV when RNAs were extracted with SDS and phenol and analyzed by nondenaturing gel electrophoresis. However, electrophoresis of denatured RNAs showed five RNAs of ~3.01, 1.18, 0.81, 0.78, and 0.52 × 10⁶ relative mass (M_r). The ds-RNA species detected in purified nucleoprotein preparations coelectrophoresed with ds-RNAs extracted from MStpV-infected tissues, except that one small ds-RNA (~0.66 × 10⁶ M_r) was found in tissue extracts and not in nucleoprotein samples. The nucleoprotein ds-RNAs were estimated to be ~4.9, 2.58, 1.73, 1.67, and 0.87 × 10⁶ M_r under nondenaturing conditions. Denatured ss- and ds-RNAs separated by 2M LiCl fractionation had identical mobilities, suggesting that the ds-RNAs are complementary to the respective ss-RNAs. The sizes of the ss- and ds-RNAs in individual nucleoprotein components were proportional to the sedimentation coefficients. The nucleoprotein 0.52 × 10⁶ ss- and 0.87 × 10⁶ ds-RNAs were isolated from the slowest-sedimenting component (70S), while the 3.01 × 10⁶ ss- and 4.9 × 10⁶ ds-RNAs were isolated from the fastest-sedimenting component. Nondenaturing electrophoresis of RNAs isolated and electrophoresed immediately from purified individual nucleoprotein components showed mostly ss-RNAs, whereas SDS and phenol extraction yielded both ss- and ds-RNAs. The possibility that only ss-RNAs are encapsidated during virion assembly, and that ds-RNAs arise during RNA extraction is discussed.