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Zongrang Liu, Ralph Scorza, Jean-Michel Hily, Simon W. Scott, and Delano James

silencing mechanism ( Baulcombe, 1996b ). During the silencing process, the dsRNAs (formed from aberrant transcripts in transgenic plants, RNA transcripts that produce hairpins through inverted repeats, or RNA virus replicate intermediates) are degraded into

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Rodrigo A. Valverde and James F. Fontenot

Abbreviation: dsRNA, double-stranded ribonucleic acid. 1 Assistant Professor. 2 Professor, Dept. of Horticulture. Approved for publication by the Director of the Louisiana Agricultural Experiment Station as manuscript no. 90-38-4020. We thank B

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S.T. Nameth and S.L. Cheng

Double-stranded ribonucleic acid (dsRNA) analysis of apparently healthy red mulberry (Morus rubra L.) yielded four distinct dsRNA banding profiles. dsRNA type 1 contained three dsRNA bands with approximate molecular weights (MWs) of 12.0, 1.0, and 0.9 × 106, respectively. dsRNA type 2 contained two dsRNA bands with MWs of 1.0 and 0.9 × 106. dsRNA type 3 contained four dsRNA bands with MWs of 1.0, 0.9, 0.89, and 0.88 × 106. dsRNA type 4 contained three dsRNA bands with MWs of 1.0, 0.88, and 0.87 × 106. No virus particles were associated with any of the samples analyzed. All four types of dsRNA were resistant to DNase I and RNase A in high salt and susceptible to RNase A in low salt. Mulberry dsRNAs were somewhat similar to endogenous dsRNAs (edsRNA) associated with other hosts. This is the first report of edsRNA associated with a deciduous tree.

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G.E. Holcomb and R.A. Valverde

Salvia uliginosa Benth. plants, in an experimental planting of Salvia species, exhibited virus-like symptoms of chlorotic line patterns and ringspots. The suspect virus was mechanically transmitted to several experimental hosts and was identified as cucumber mosaic cucumovirus (CMV) based on dsRNA gel patterns, positive reaction with CMV antiserum, and particle morphology as observed by transmission electron microscopy.

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M-C Sanchez-Cuevas and S.G.P. Nameth

Double petunia plants expressing virus-like symptoms were collected in greenhouses and garden centers throughout Ohio in Spring 1997 and 1998 in an effort to determine the frequency and distribution of petunia viruses present in the state. Direct antibody-sandwich and indirect enzyme-linked immunosorbent assay (ELISA) were conducted with commercial antisera made against 13 viruses, a potyvirus kit capable of detecting 80 different potyviruses, and our antiserum raised against a tobamo-like virus inducing severe mosaic in double petunia. Viral-associated double-stranded ribonucleic acid (dsRNA) analysis and light microscopy for detection of inclusion bodies were also carried out. ELISA, dsRNA analysis, and light microscopy revealed the presence of tobacco mosaic tobamovirus, an unknown tobamo-like petunia virus, tomato ringspot nepovirus, tobacco streak ilarvirus, and tobacco ringspot nepovirus. Tomato aspermy cucumovirus, tomato spotted wilt tospovirus, impatiens necrotic spot tospovirus, alfalfa mosaic virus, cucumber mosaic cucumovirus, potato virus X potexvirus, and chrysanthemum B carlavirus were not detected. No potyviruses were identified. A number of plants with virus-like symptoms tested negative for all viruses.

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J.R. Fisher and S.T. Nameth

Ajuga reptans L. is an herbaceous ornamental mint grown in borders or as a groundcover, and is commonly propagated vegetatively and by seed. Three hundred and fifty-six A. reptans samples were obtained from growers in Washington, Michigan, Iowa, and Ohio, and screened for alfalfa mosaic virus (AMV), tobacco streak ilarvirus (TSV), cucumber mosaic cucumovirus (CMV), tomato aspermy cucumovirus (TAV), tomato spotted wilt tospovirus (TSWV), impatiens necrotic spot tospovirus (INSV), tobacco mosaic tobamovirus (TMV), potato virus × potexvirus (PVX), and 80 potyviruses, using direct antibody sandwich (DAS) and indirect enzyme-linked immunosorbent assay (ELISA). Viral-associated double-stranded ribonucleic acid (dsRNA) analysis was used to detect an apparent satellite (sat) RNA, and northern hybridization using a digoxigenin (DIG) labeled (S) CARNA-5 cDNA probe was used to confirm the identity of the apparent satRNA. No incidences of TAV, TMV, TSWV, INSV, PVX, or potyviruses were detected. CMV was detected in 11%, AMV in 22.2%, TSV in 3.7%, and mixed infections of CMV and AMV in 1.1% of the samples. SatRNA was detected in 36 A. reptans `Royalty', two `Rainbow', and two `Burgundy Glow' samples by dsRNA analysis, and confirmed by hybridization in 29 `Royalty' and one `Burgundy Glow' samples. Sixteen A. reptans `Royalty' seedlings grown from seed harvested from CMV-infected plants were tested by ELISA for CMV, AMV, and TSV. All were positive for CMV, and two were positive for a mixed infection of CMV and AMV. SatRNA was detected in all 16 seedlings by RT-PCR.

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Elysia K. Krieger, Edwards Allen, Larry A. Gilbertson, James K. Roberts, William Hiatt, and Rick A. Sanders

Hiatt (2005) , these plants contain T-DNAs linked at the left borders. While this configuration results in inverted PG repeats, the promoter orientation would not be expected to generate a dsRNA precursor. Previous reports show using a single copy of

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Jean-Michel Hily, Michel Ravelonandro, Vern Damsteegt, Carole Bassett, Cesar Petri, Zongrang Liu, and Ralph Scorza

), which is derived from double-stranded RNA (dsRNA), which seems to play a central role in triggering sequence-specific RNA degradation. These siRNAs, corresponding to both sense and antisense strands, guide a multisubunit ribonuclease, the RNA

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Robert J. Griesbach, Ronald M. Beck, John Hammond, and John R. Stommel

1 methylates the 2′-OH of the 3′-terminal nucleotide. The miRNA then forms an imperfect double-stranded RNA (dsRNA) that is transported out of the nucleus by the Exporetin-5 protein (HST). The dsRNA is rapidly unwound in the cytoplasm and is

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Madhurababu Kunta, J.V. da Graça, and Mani Skaria

were harvested during the summer months when growth conditions are optimum for viroids ( Roistacher, 1991 ). Preparation of nucleic acid extracts with viroid RNA targets. The method used for extraction of dsRNAs from plant tissue was an