Controlling Geminiviruses before Transmission: Prospects

Endosymbionts as hidden players in tripartite pathosystem of interactions and potential candidates for sustainable viral disease management

The convoluted relationships between plants, viruses, and arthropod vectors housing bacterial endosymbionts are pivotal in the spread of harmful plant viral diseases. Endosymbionts play key roles in: manipulating host responses, influencing insect resistance to pesticides, shaping insect evolution, and bolstering virus acquisition, retention, and transmission. This interplay presents an innovative approach for developing sustainable strategies to manage plant diseases. Recent progress in targeting specific endosymbionts through genetic modifications, biotechnological advancements, and RNA interference shows potential for curbing viral spread and disease progression. Additionally, employing synthetic biology techniques like CRISPR/Cas9 to engineer endosymbionts and disrupt crucial interactions necessary for viral transmission in arthropod vectors holds promise for effective control measures. In this review, these obligate and facultative bacterial cruxes have been discussed to elaborate on their mechanistic involvement in the regulation and/or inhibition of tripartite pathways of interactions. Furthermore, we provide an in-depth understanding of endosymbionts' synergistic and antagonistic effects on: insect biology, plant immunity, and virus acquisition and transmission. Finally, we point out open questions for future research and provide research directions concerning the deployment of genetically engineered symbionts to affect plant-virus-vector interactions for sustainable disease management. By addressing existing knowledge gaps and charting future research paths, a deeper comprehension of the role of endosymbionts in plant-virus-vector interactions can pave the way for innovative and successful disease management strategies. The exploration of antiviral therapies, paratransgenesis, and pathogen-blocking tactics using engineered endosymbionts introduces pioneering solutions for lessening the impact of plant viral diseases and green pest management.

The rising threat of geminiviruses: molecular insights into the disease mechanism and mitigation strategies

BACKGROUND

Geminiviruses are among the most threatening emerging plant viruses, accountable for a huge loss to agricultural production worldwide. These viruses have been responsible for some serious outbreaks during the last few decades across different parts of the world. Sincere efforts have been made to regulate the disease incidence by incorporating a multi-dimensional approach, and this process has been facilitated greatly by the advent of molecular techniques. But, the mixed infection due to the polyphagous nature of vectors results in viral recombination followed by the emergence of novel viral strains which thus renders the existing mitigation strategies ineffective. Hence, a multifaceted insight into the molecular mechanism of the disease is really needed to understand the regulatory points; much has been done in this direction during the last few years. The present review aims to explore all the latest developments made so far and to organize the information in a comprehensive manner so that some novel hypotheses for controlling the disease may be generated.

METHODS AND RESULTS

Starting with the background information, diverse genera of geminiviruses are listed along with their pathological and economic impacts. A comprehensive and detailed mechanism of infection is elaborated to study the interactions between vector, host, and virus at different stages in the life cycle of geminiviruses. Finally, an effort isalso made to analyze the progress made at the molecular level for the development of various mitigation strategies and suggest more effective and better approaches for controlling the disease.

CONCLUSION

The study has provided a thorough understanding of molecular mechanism of geminivirus infection.

Pervasive Endosymbiont Arsenophonus Plays a Key Role in the Transmission of Cotton Leaf Curl Virus Vectored by Asia II-1 Genetic Group of Bemisia tabaci

Insects often coevolved with their mutualistic partners such as gut endosymbionts, which play a key in the physiology of host. Studies on such interactions between Bemisia tabaci and its primary and secondary endosymbionts have gained importance due to their indispensable roles in the biology of this insect. Present study reports the predominance of two secondary endosymbionts, Arsenophonus and Cardinium in the Asia II-1 genetic group of whitefly and elucidates their role in the transmission of its vectored Cotton leaf curl virus. Selective elimination of endosymbionts was optimized using serial concentration of ampicillin, chloramphenicol, kanamycin, tetracycline, and rifampicin administered to viruliferous whiteflies through sucrose diet. Primary endosymbiont, Portiera was unresponsive to all the antibiotics, however, rifampicin and tetracycline at 90 μg/ml selectively eliminated Arsenophonus from the whitefly. Elimination of Arsenophonus resulted in significant decrease in virus titer from viruliferous whitefly, further the CLCuV transmission efficiency of these whiteflies was significantly reduced compared to the control flies. Secondary endosymbiont, Cardinium could not be eliminated completely even with higher concentrations of antibiotics. Based on the findings, Arsenophonus plays a key role in the retention and transmission of CLCuV in the Asia II-1 genetic group of B. tabaci, while the role of Cardinium could not be established due to its unresponsiveness to antibiotics.