Comparative reactions of recombinant papaya ringspot viruses with chimeric coat protein (CP) genes and wild-type viruses on CP-transgenic papaya. J Gen Virol

Cornell University, Итак, New York, United States
Journal of General Virology (Impact Factor: 3.18). 12/2001; 82(Pt 11):2827-36. DOI: 10.1099/0022-1317-82-11-2827
Source: PubMed


Transgenic papaya cultivars SunUp and Rainbow express the coat protein (CP) gene of the mild mutant of papaya ringspot virus (PRSV) HA. Both cultivars are resistant to PRSV HA and other Hawaii isolates through homology-dependent resistance via post-transcriptional gene silencing. However, Rainbow, which is hemizygous for the CP gene, is susceptible to PRSV isolates from outside Hawaii, while the CP-homozygous SunUp is resistant to most isolates but susceptible to the YK isolate from Taiwan. To investigate the role of CP sequence similarity in overcoming the resistance of Rainbow, PRSV HA recombinants with various CP segments of the YK isolate were constructed and evaluated on Rainbow, SunUp and non-transgenic papaya. Non-transgenic papaya were severely infected by all recombinants, but Rainbow plants developed a variety of symptoms. On Rainbow, a recombinant with the entire CP gene of YK caused severe symptoms, while recombinants with only partial YK CP sequences produced a range of milder symptoms. Interestingly, a recombinant with a YK segment from the 5' region of the CP gene caused very mild, transient symptoms, whereas recombinants with YK segments from the middle and 3' parts of the CP gene caused prominent and lasting symptoms. SunUp was resistant to all but two recombinants, which contained the entire CP gene or the central and 3'-end regions of the CP gene and the 3' non-coding region of YK, and the resulting symptoms were mild. It is concluded that the position of the heterologous sequences in the recombinants influences their pathogenicity on Rainbow.

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Available from: Fuh-Jyh (F.-J.) Jan, May 30, 2014
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    • "Pathogen derived resistance is governed either by protein-mediated or RNA-mediated methods. An alternative strategy using RNA-mediated gene silencing with transgenic plants expressing viral genes has been developed [57]. Resistance levels of PRSV differ with environmental factors and plant development stages despite of the success with this approach. "
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    ABSTRACT: Papaya (Carica papaya) is severely damaged by the papaya ringspot virus (PRSV). This review focuses on the development of PRSV resistant transgenic papaya through gene technology. The genetic diversity of PRSV depends upon geographical distribution and the influence of PRSV disease management on a sequence of PRSV isolates. The concept of pathogen-derived resistance has been employed for the development of transgenic papaya, using a coat protein-mediated, RNA-silencing mechanism and replicase gene-mediated transformation for effective PRSV disease management. The development of PRSV-resistant papaya via post-transcriptional gene silencing is a promising technology for PRSV disease management. PRSV-resistant transgenic papaya is environmentally safe and has no harmful effects on human health. Recent studies have revealed that the success of adoption of transgenic papaya depends upon the application, it being a commercially viable product, bio-safety regulatory issues, trade regulations, and the wider social acceptance of the technology. This review discusses the genome and the genetic diversity of PRSV, host range determinants, molecular diagnosis, disease management strategies, the development of transgenic papaya, environmental issues, issues in the adoption of transgenic papaya, and future directions for research.
    Full-text · Article · Mar 2014 · The Scientific World Journal
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    • "The development of a system to produce infectious viral transcripts from recombinant PRSV in vitro (Chiang and Yeh, 1997) has provided a unique opportunity to begin to identify viral-encoded gene segments involved in various viral functions, including pathogenicity, host range and vector transmission (Chen et al ., 2001b; Lee et al ., 2001), as well as to probe the mechanisms involved in induced virus resistance caused by crossprotection and transgene-induced post-transcriptional gene silencing (Chiang et al ., 2001; You et al ., 2005). The results of bioassay studies with in vitro transcripts of recombinant PRSV-W with its CP gene replaced with that of a CP gene from PRSV-P demonstrated that the CP gene is not a determinant for infection of papaya (Chen et al ., 2001b). "
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    ABSTRACT: TAXONOMY: Papaya ringspot virus (PRSV) is an aphid-transmitted plant virus belonging to the genus Potyvirus, family Potyviridae, with a positive sense RNA genome. PRSV isolates belong to either one of two major strains, P or W. The P strains infect both papaya and cucurbits whereas the W strains infect only cucurbits. GEOGRAPHICAL DISTRIBUTION: PRSV-P is found in all major papaya-growing areas. PHYSICAL PROPERTIES: Virions are filamentous, non-enveloped and flexuous measuring 760-800 x 12 nm. Virus particles contain 94.5% protein and 5.5% nucleic acid. The protein component consists of the virus coat protein (CP), which has a molecular weight of about 36 kDa as estimated by Western blot analysis. Density of the sedimenting component in purified PRSV preparations is 1.32 g/cm(3) in CsCl. GENOME: The PRSV genome consists of a unipartite linear single-stranded positive sense RNA of 10 326 nucleotides with a 5' terminus, genome-linked protein, VPg. TRANSMISSION: The virus is naturally transmitted via aphids in a non-persistent manner. Both the CP and helper component (HC-Pro) are required for vector transmission. This virus can also be transmitted mechanically, and is typically not seed-transmitted. HOSTS: PRSV has a limited number of hosts belonging to the families Caricaceae, Chenopodiaceae and Cucurbitaceae. Propagation hosts are: Carica papaya, Cucurbita pepo and Cucumis metuliferus cv. accession 2459. Local lesion assay hosts are: Chenopodium quinoa and Chenopodium amaranticolor. CONTROL: Two transgenic papaya varieties, Rainbow and SunUp, with engineered resistance to PRSV have been commercially grown in Hawaii since 1998. Besides transgenic resistance, tolerant varieties, cross-protection and other cultural practices such as isolation and rogueing of infected plants are used to manage the disease. VIRUS CODE: VIRUS ACCESSION NUMBER: 57010045. USEFUL LINK:
    Full-text · Article · Jun 2008 · Molecular Plant Pathology
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    • "With a discovery that some geographically distant PRSV viruses are able to overcome the coat protein mediated resistance in papaya, it was originally suggested, that the resistance to the PRSV is strain specific and it must therefore be targeted to strains from the same geographical region (Tennant et al. 1994). More recent reports have shown however, that the sequence divergence of the virus from the transgene does not always correlate with the ability to overcome PRSV resistance (Chiang et al. 2001). An involvement of silencing suppressor seems to be more likely the main factor involved in breaking of PRSV transgenic resistance (Tripathi et al. 2004). "
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    ABSTRACT: Transgenic papayas carrying the papaya ringspot virus coat protein gene were inoculated with Papaya ringspot virus. Infection was monitored by evaluating symptoms and by reverse transcription polymerase chain reaction (RT-PCR). Among eight tested transgenic lines, clone G2 was found highly resistant to virus infection during 3 years of testing. Further analysis of this clone revealed complex multicopy transgene insertion with aberrant copies. The suspected post transcriptional gene silencing was confirmed by siRNA detection. While the R0 generation of G2 transgenic papaya was found to be fully resistant to the infection, Papaya ringspot virus was able to break this resistance in subsequent generations by suppressing post-transcriptional gene silencing (PTGS).
    Full-text · Article · Aug 2007 · Biologia Plantarum
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