Development of Transgenic Papaya through Agrobacterium-Mediated Transformation

Recent development of oral vaccines (Review)

Oral immunization can elicit an effective immune response and immune tolerance to specific antigens. When compared with the traditional injection route, delivering antigens via the gastrointestinal mucosa offers superior immune effects and compliance, as well as simplicity and convenience, making it a more optimal route for immunization. At present, various oral vaccine delivery systems exist. Certain modified bacteria, such as Salmonella, Escherichia coli and particularly Lactobacillus, are considered promising carriers for oral vaccines. These carriers can significantly enhance immunization efficiency by actively replicating in the intestinal tract following oral administration. The present review provided a discussion of the main mechanisms of oral immunity and the research progress made in the field of oral vaccines. Additionally, it introduced the advantages and disadvantages of the currently more commonly administered injectable COVID-19 vaccines, alongside the latest advancements in this area. Furthermore, recent developments in oral vaccines are summarized, and their potential benefits and side effects are discussed.

DsRNA-mediated protection against two isolates of Papaya ringspot virus through topical application of dsRNA in papaya

Papaya ringspot virus (PRSV) infections in papaya result in heavy yield losses, severely affecting the papaya industry worldwide, and hence warranting for effective control measures. In the past, transgenic papaya cultivars were developed that overexpressed parts of the PRSV genome and exhibited high levels of virus resistance. In the present study, a non-transgenic approach was employed, in which in vitro produced dsRNA molecules derived from a PRSV isolate from South India (PRSV-Tirupati) was tested for dsRNA-mediated protection against two isolates of PRSV through topical application of the dsRNA on papaya. The results showed that the dsRNA molecules from both the coat protein (CP) and helper component-proteinase (HC-Pro) genes of the PRSV-Tirupati isolate conferred 100 % resistance against PRSV-Tirupati infection. Further, the same dsRNA molecules were highly effective against the PRSV-Delhi isolate on the papaya cv. Pusa Nanha, conferring a resistance of 94 % and 81 %, respectively. Systemic papaya leaves of the dsRNA-treated plants were virus-free at 14 days post-inoculation, confirming the robustness of this non-transgenic virus control strategy. In contrast, the control TMV dsRNA did not protect against the PRSV infection. This study on the topical application of dsRNA opened up a new avenue for the control of papaya ringspot disease worldwide.

Gene technology for papaya ringspot virus disease management

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.