• Fellow, Indian National Science Academy, New Delhi
• Fellow, Indian Academy of Sciences, Bangalore
• Fellow, National Academy of Sciences India, Allahabad
• Member, Editorial Board, Journal of Biosciences
• Member, Editorial Board, Virus Disease
• Visiting Professorship, Northwest University of Agriculture and Forestry, China
• J. C. Bose Fellowship.

Plant viruses have historically attracted the attention of researchers because of the diseases they cause in plants and the role they play in determining crop yields in most regions of the tropics. More recently, plant viruses have emerged as models to understand intracellular trafficking and tools to develop gene expression and gene silencing platforms. Plant viral genomes, because of their small size are interesting cases of rapid adaptation and co-evolution with their hosts under changing agricultural scenario. Genes encoded by plant viruses often are masters of multi-tasking and their interactions with their host defence systems are broadening our understanding of their evolution. With these broad perspectives in mind, our group has been active in studying plant viruses.

Transgenic virus resistance: Working with viruses causing the tungro disease of rice, our group has developed transgenic rice plants showing resistance against Indian isolates of Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV), using RNAi technology. The above resistance has now been diversified to several rice varieties popular in the eastern and southern regions of our country by marker-assisted backcross breeding, in collaboration with scientists in Tamil Nadu and West Bengal. Working with the highly infectious Tomato leaf curl New Delhi virus, a virus rapidly spreading to new regions of the World and to new plant hosts, we have developed a novel form of resistance, based on trans-acting siRNAs.

Viral variability:Although rice tungro viruses have been reported from the entire South and South-east Asian region, our group has shown RTBV to be more variable than RTSV. Working with viruses infecting cassava, citrus, mentha and okra (bhendi), our group has revealed new information on their variability and genetic relationship with similar viruses in India and abroad. We have developed infectious clones of viruses infecting cassava (Sri Lankan cassava mosaic virus, SLCMV), which is being used to investigate its gene functions and interactions with the host plants. We have also looked at the role of whitefly vectors in transmission of SLCMV and the importance of amino acid residues of the viral coat protein in determining the symptoms.

Viral promoters:We found new and interesting gene expression control elements embedded in the promoter of an Indian isolate of RTBV. We went on to show their functional significance in controlling heterologous gene expression. This has led to an international patent on its use (US Patent no. 07728122, Eurasian patent no. 013229) awarded jointly to Department of Biotechnology, Government of India and University of Delhi for its use. The promoter has been commercialized with the help of Biotech Consortium India Limited. Subsequently, we have also shown the existence of negative control elements in the RTBV promoter.

VIGS:To use viruses as tools for gene silencing, we have developed RTBV into a VIGS vector and demonstrated its effectiveness in silencing genes of rice, with a view to strengthen functional genomic initiatives for monocots. This has been awarded an Indian patent (No. 278167). For more information click here

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• Agroinoculation of rice