Research Projects

Begomoviruses are economically important group of plant viruses which infect large number of horticultural and ornamental crop species in tropical and sub tropic areas worldwide. Begomoviruses belong to the family Geminiviridae and are characterized by a single-stranded circular DNA genome of about 2.8 kb in a twin icosahedral capsid (Rojas et al., 2018). Begomoviruses are being transmitted by insect vector whitefly (Bemisia tabaci). Tomato leaf curl Gujarat virus (ToLCGV) is the predominant begomovirus species in India causing up to 100% crop losses (Chakraborty 2008). Management of ToLCGV is difficult due to ability of whitefly populations to reach high numbers and their ability to develop pesticide resistance (Polston and Lapidot 2007). Autophagy is a highly conserved process in eukaryotes responsible for degrading and recycling cytoplasmic contents, including damaged organelles, protein aggregates, and invading pathogens through double-membrane vesicle. Autophagy is a multi-step process which includes activation, nucleation, and elongation of phagophore, autophagosome maturation, fusion with lysosome (in animals) and vacuole (in plants), following degradation and recycling. Autophagy is regulated through different autophagy-related genes (ATGs). In plants, autophagy serves as a critical component of immunity, stress adaptation, and cellular homeostasis. Similarly, in insects such as the whitefly, autophagy contributes to responses against pathogens and environmental stresses. Plants and insect vectors have developed different strategies to fight against plant viruses. Emerging evidences have suggested that autophagy plays an important role in plants and whitefly against begomoviruses. Some reports have revealed that autophagy can suppress viral infections by degrading viral proteins in plants. On other hand, few reports have also shown that viruses can also subvert the autophagy to promote their own replication and persistence in the host plants. Only a few reports suggest that various viruses can upregulate the expression of different ATGs in whitefly. However, mechanism of activation of autophagy in both the host plant and its insect vector has not been investigated till date. This knowledge gap motivates us to conduct a detailed study on mechanism of autophagy activation following ToLCGV infection. Proposed work aims (i) to identify the host factor/s activates ToLCGV induced autophagy and, (ii) to recognize the viral protein/s that trigger autophagy. Further, functional characterization of autophagy activating host factor will be carried out and its role in regulating viral titre will also be investigated. Finally, begomovirus tolerant Nicotiana benthamiana plant will be engineered exploiting autophagy phenomenon. Previous studies have shown that autophagy provides tolerance to host plant and vector against DNA or RNA virus. However, none of the studies have explored the mechanism of autophagy activation triggered by virus. Here we hypothesize that specific begomovirus encoded protein might be targeted by specific plant and insect proteins which belong to the pre-autophagosomal structure (PAS) or upstream to the PAS. The research will employ advanced molecular biology techniques such as qRT-PCR and western blotting for differential gene expression. Interaction of host – virus and host-host proteins will be studied by Y2H and confirmed by CoIP and BiFC assays. Localization of proteins will be studied through confocal microscopy. Gene silencing in plants and whitefly will be done by TRV based VIGS and dsRNA feeding, respectively. Genetically engineered N. benthamiana plants will be developed through Agrobacterium mediated transformation. Identifying key autophagy activating components which restrict begomoviruses accumulation could be a new molecular targets for breeding virus-resistant crops. Proposed study will add the knowledge of autophagy activation machineries.