Allergenicity Assessment of the Papaya Ringspot Virus Coat Protein Expressed in Transgenic Rainbow Papaya
The virus-resistant, transgenic commercial papaya Rainbow and SunUp (Carica papaya L.) have been consumed locally in Hawaii and elsewhere in the mainland United States and Canada since their release to planters in Hawaii in 1998. These papaya are derived from transgenic papaya line 55-1 and carry the coat protein (CP) gene of papaya ringspot virus (PRSV). The PRSV CP was evaluated for potential allergenicity, an important component in assessing the safety of food derived from transgenic plants. The transgene PRSV CP sequence of Rainbow papaya did not exhibit greater than 35% amino acid sequence homology to known allergens, nor did it have a stretch of eight amino acids found in known allergens which are known common bioinformatic methods used for assessing similarity to allergen proteins. PRSV CP was also tested for stability in simulated gastric fluid and simulated intestinal fluid and under various heat treatments. The results showed that PRSV CP was degraded under conditions for which allergenic proteins relative to nonallergens are purported to be stable. The potential human intake of transgene-derived PRSV CP was assessed by measuring CP levels in Rainbow and SunUp along with estimating the fruit consumption rates and was compared to potential intake estimates of PRSV CP from naturally infected nontransgenic papaya. Following accepted allergenicity assessment criteria, our results show that the transgene-derived PRSV CP does not pose a risk of food allergy.
Available from: Decai Tuo
- "PRSV-resistant transgenic papayas engineered with the CP or NIb gene have been commercialized in Hawaii and China, respectively, representing the first commercialized transgenic fruit crop (Gonsalves, 1998; Gonsalves et al., 2008; Ye and Li, 2010). However, these commercialized transgenic papayas resistant to PRSV, like SHEN, W. et al.: RESISTANCE OF PAPAYAS TO PRSV MEDIATED BY ihpRNA EXPRESSED IN BACTERIA other genetically modified organisms, are disputed regarding their potential risks to human health and the environment, although their safety has been assessed (Fermín et al., 2011; Lin et al., 2013; Tecson Mendoza, et al., 2008). PRSV resistance in commercialized transgenic papaya in Hawaii relies on RNA-mediated mechanisms or post-transcriptional gene silencing (PTGS), not CP protein-mediated resistance (Tennant et al., 2001; Souza et al., 2005; Tripathi et al., 2008). "
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ABSTRACT: RNA-mediated virus resistance based on natural antiviral RNA silencing has been exploited as a powerful tool for engineering virus resistance in plants. In this study, a conserved 3'-region (positions 9839-10117, 279 nt) of the capsid protein (CP) gene of papaya ringspot virus (PRSV), designated CP279, was used to generate an intron-containing hairpin RNA (ihpRNA) construct by one-step, zero-background ligation-independent cloning (OZ-LIC). The RNaseIII-deficient Escherichia coli strain M-JM109lacY was identified as the best choice for producing large quantities of specific ihpRNA-CP279. Resistance analyses and ELISA data verified that most papaya plants mechanically co-inoculated with TRIzol-extracted ihpRNA-CP279 and PRSV were resistant to PRSV, and resistance was maintained throughout the test period (>2 months post-inoculation). In contrast, a 1-2 day interval between sequential inoculation of PRSV and ihpRNA-CP279 did not result in complete protection against PRSV infection, but delayed the appearance of viral symptoms by 3 to 4 days. These findings indicate that direct mechanical inoculation of papaya plants with bacterially-expressed ihpRNA-CP279 targeting the PRSV CP gene can interfere with virus infection. This work lays a foundation for developing a non-transgenic approach to control PRSV by directly spraying plants with ihpRNA or crude bacterial extract preparations.
Available from: PubMed Central
- "Yeh and Gonsalves  reported that there were no ill effects after the consumption of PRSV-resistant transgenic papaya. Fermín et al.  observed that transgene derived PRSV CP did not pose any risk of food allergies. Transgenic papaya fruit can be recognised as an equivalent substitution for traditional papaya in food safety . "
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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.
Available from: Kazunari Kondo
- "Hawaiian non-GM (Sunset) and two cultivars of 55-1 (SunUp and Rainbow) were purchased from a trade agency via the Hawaii Papaya Industry Association. SunUp is a homozygote generated by transforming the non-transgenic inbred cultivar Sunset, whereas Rainbow is a first filial generation (F 1 ) hybrid from a cross between SunUp and non-transgenic Kapoho (Fermín et al., 2011). Thirtyeight commodities from eight types of processed papaya products (canned papaya, pickled papaya, dried fruit, papaya-leaf tea, jam, puree, juice, frozen dessert) were purchased online (Supplementary Table 1). "
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ABSTRACT: Genetically modified (GM) papaya (Carica papaya L.) line 55-1 (55-1), which is resistant to papaya ringspot virus infection, has been marketed internationally. Many countries have mandatory labeling regulations for GM foods, and there is a need for specific methods for detecting 55-1. Here, an event- and construct-specific real-time polymerase chain reaction (PCR) method was developed for detecting 55-1 in papaya products. Quantitative detection was possible for fresh papaya fruit up to dilutions of 0.001% and 0.01% (weight per weight [w/w]) for homozygous SunUp and heterozygous Rainbow cultivars, respectively, in non-GM papaya. The limit of detection and quantification was as low as 250 copies of the haploid genome according to a standard reference plasmid. The method was applicable to qualitative detection of 55-1 in eight types of processed products (canned papaya, pickled papaya, dried fruit, papaya-leaf tea, jam, puree, juice, and frozen dessert) containing papaya as a main ingredient.
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