Research Projects

Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite geminivirus known to cause devastating damage to the production of tomato, chilli, and cucurbits in the country. As the name suggests, first it was reported to infect only tomato plants but now it is reported to infect about 43 other plant species of different families. ToLCNDV induces severe symptoms including leaf curling (upward or downward), vein clearing, shortening of internodal distance, and abnormal leaf margins. Later, the infected plants appear severely stunted and display weakened fruit settings, leading to complete crop loss. A molecular investigation followed by breeding practices identified a few dominant and recessive alleles such as Ty-1,2,3,4,5 and 6 which can confer tolerance against ToLCNDV. Recently, we have identified resistance (R) gene SW5a that induces a strong immune response upon sensing viral effector AC4 in tomato. However, emerging strains of these deadly viruses have been reported from various parts of the world which can breach R-gene-mediated resistance. Few reports suggested the involvement of several components of RNAi response such as RDRs, DCLs, and AGOs in restricting geminiviral propagation. However, ToLCNDV also encodes several suppressors of RNAi such as AC2, AC4, and AV2 to counter this response. In conclusion, there are very few effective sources of resistance to geminiviruses, necessitating the identification and characterization of novel sources of resistance. To explore the molecular basis of resistance, a transcriptome study involving geminivirus tolerant and susceptible plant variety was carried out in our laboratory. Among several differentially regulated transcripts, we have identified a novel host factor geminivirus tolerance factor 1 (GTF1), significantly upregulated during geminivirus infection in a plant resistant to geminivirus. In-silico analysis of this uncharacterized gene showed its presence in tomato genome. Further, the gene was cloned from tomato to explore its role in viral pathogenesis. Transient ectopic expression of SlGTF1 showed a significant decrease in ToLCNDV titer whereas upon silencing of the gene viral titer was significantly increased (unpublished data), suggesting this uncharacterized protein's anti-viral role as an immune modulator. The present study will therefore elucidate the mechanism of SlGTF1 in immune modulation in tomato and the identification of host signalling processes. Understanding this molecular interplay will pave the way for a potential candidate gene that can be altered to enhance plant resistance. SlGTF1 is neither an R gene nor it can be placed in RNAi pathways or hormone signalling pathways, the major antiviral pathways identified so far in plants.