Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
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Wild larkspur, Delphinium glaucum S. Watson, grows throughout most of Alaska along roadsides and in forests and is planted as an ornamental. Leaves containing distinct vein-clearing and chlorotic mosaic symptoms were first noticed on several D. glaucum plants during 2000 at the Georgeson Botanical Garden in Fairbanks, AK. Although affected plants continued to produce normal flowers, by 2008, the plants developed overall stunting. Initially, virus presence was determined by a general differential centrifugation extraction and concentration protocol followed by examination of the partially purified virus and leaf sap by electron microscopy. Filamentous particles approximately 725 nm long were observed. Virion protein extractions analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a putative coat protein (CP) of ~35 kDa. Potyvirus identity (family Potyviridae) was confirmed with universal potyvirus antiserum in western blots and ELISA assays (Agdia, Inc., Elkhart, IN). Exotic larkspur plants, D. elatum L., growing next to diseased D. glaucum plants, did not exhibit symptoms nor were they positive for potyvirus when tested serologically as described previously. Total RNA was extracted from potyvirus-infected leaves and used in reverse transcriptase-PCR assays that specifically targeted potyviruses (2,4) to generate genomic segments for identification and sequence analysis. Fragments representing portions of the helper component protease gene, HC-Pro (~700 bp), the cylindrical inclusion gene, CI (~700 bp), and the 3'-end (~1.7 kbp) were purified, cloned, sequenced, and deposited in GenBank (Accession Nos. FJ349329, FJ349328, and FJ349327, respectively). The sequenced 3'-end (1,674 nt) revealed a partial nuclear inclusion protein gene, NIb (1 to 630 nt), a CP gene (631 to 1,443 nt), and a 3'-untranslated region (1,447 to 1,674 nt) attached to a poly (A) tail. Blast searches in GenBank for percent identities of the nucleotide and amino acid comparisons resulted in highest similarities in conserved regions among members in the genus Potyvirus. For example, the highest CI, CP, and HP amino acid identities (0 gaps) were 67% with Potato virus A (Accession No. AF543709), 74% with Araujia mosaic virus (Accession No. EF710625), and 65% with Potato virus A (Accession No. AJ131403), respectively. However, none of the identities were sufficient for inclusion with an existing potyvirus species, whereby the CP amino acid sequence identity must be at least 80% (1). Mechanical transmission of purified virus to Chenopodium amaranticolor, C. quinoa, D. elatum, D. glaucum, and Nicotiana benthamiana seedlings was unsuccessful. We conclude that the isolated virus is a new species in the genus Potyvirus and propose the name Delphinium vein-clearing virus (DeVCV). To our knowledge, this is the first report of a virus isolated from D. glaucum and is representative of the growing number of viruses found in native plants (3). The distribution of DeVCV-infected larkspur is not known in managed or natural ecosystems. Identification of new viruses from native plants is important, in that, the host plant may act as a virus reservoir for transmission to other ornamental and crop plants. References: (1) P. H. Berger et al. Family Potyviridae. Page 819 in: Virus Taxonomy-8th Report of the ICTV. C. M. Fauquet et al., eds. Elsevier Academic Press, San Diego, CA, 2005. (2) J. Chen et al. Arch. Virol. 146:757, 2001. (3) I. Cooper and A. C. Jones. Adv. Virus Res. 67:1, 2006. (4) C. Ha et al. Arch. Virol. 153:25, 2008.
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PMID:Identification and Molecular Characterization of a Potyvirus Isolated from Native Larkspur (Delphinium glaucum) in Alaska. 3076 48

Papaya rinsgpot virus type P (PRSV), a member of the genus Potyvirus in the family Potyviridae, is primarily transmitted by aphids in a nonpersistent manner (2). The virus is geographically widespread but has a narrow host range within the plant families Caricaceae, Chenopodiaceae, and Cucurbitaceae (2). The first reported epidemic of PRSV in Jamaica was during the late 1980s (1). Since then, the virus has spread across the island and is recognized as a potential problem for continued production of papaya (Carica papaya L.). In the summers of 1999 and 2000, prominent vein clearing symptoms were observed on leaves of a common weed, cerasee (Momordica charantia L.), in papaya orchards of western Jamaica. This weed, a climbing annual in the Cucurbitaceae family used in a variety of local herbal preparations, was found to be growing on fences or the ground along the periphery of the orchards. Leaf samples were collected and tested for PRSV by double-antibody sandwich (DAS)-ELISA with polyclonal antibodies (Agdia Inc, Elkhart, IN). In addition, crude sap extracts from 12 cerasee leaf samples that were diluted 1:20 were mechanically inoculated onto six plants each of cerasee and papaya. Within 2 weeks, vein clearing symptoms were observed on cerasee and symptoms (vein clearing followed by mosaic development and leaf distortions) typical of PRSV infection were obtained on papaya (2). All original leaf samples and inoculated plants tested positive in DAS-ELISA. In subsequent vector transmission tests, 10 healthy cerasee or papaya seedlings were inoculated with aphids (Aphis gossypii) that were previously permitted to feed on PRSV-infected papaya or cerasee. High rates of virus transmission were achieved in three tests from cerasee to papaya (77 to 83%), papaya to cerasee (90 to 93%), and cerasee to cerasee (60 to 70%). Total RNA from papaya samples was subjected to reverse transcriptase-PCR using primers to the capsid protein gene (3). A single fragment of the expected size (approximately 996 bp) was amplified and sequenced and showed high nucleotide identity (90.3 to 91.4%) with previously reported PRSV type P from Jamaica (GenBank Accession No. DQ104823), Cuba (GenBank Accession No. DQ089482), Florida (GenBank Accession No. AF196839), Brazil (GenBank Accession No. AF344650), and Hawaii (GenBank Accession No. S46722). To our knowledge, this is the first report of the natural occurrence of PRSV on a weed host in Jamaica. Because of its widespread distribution and potential of serving as a reservoir of PRSV, cerasee may play a role in the epidemiology of PRSV. References: (1) M. Chin et al. Jam. J. Sci. Technol. 14:58, 2003. (2) D. Purcifull et al. No 292 in: Descriptions of Plant Viruses. CMI/AAB, Surrey, England, 1984. (3) J. Slightom. Gene 100:251, 1991.
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PMID:Momordica charantia is a Weed Host Reservoir for Papaya ringspot virus Type P in Jamaica. 3078 Jul 59


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