Plant Molecular Biology Laboratory, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067.
Abstracts of the papers presented at the 16th Annual Convention and International Symposium of Indian Virological Society on “Management of Vector-Borne Viruses” at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru-502324, Hyderabad, India, February 7–10, 2006.
Geminiviruses pose serious threats to almost every crop in the tropical and subtropical countries across the globe. Using the Mungbean yellow mosaic India virus (MYMIV-Bg) as a model system, we are deciphering the mechanism of replication of the single stranded viral DNA genome inside the nucleus of the infected plant cell. Two of the virus encoded proteins, namely, the replication initiator (Rep or AL1) and the replication enhancer protein (Ren or AL3) along with other unknown host factors help multiply the viral genome employing a series of orchestrated as well as complicated steps. Here we will report on the function of the viral Rep protein that plays the major role to initiate and propagate the rolling circle replication of the bipartite viral genomes. The data on DNA-protein interaction of Rep with the virus replication origins, various important domains of Rep, interaction of Rep with host factors such as proliferating cell nuclear antigen (PCNA), single stranded DNA binding protein RPA, etc will be presented to show how the replication fork is set up and moved along. In this connection, the surprise discovery was the helicase activity of the Rep protein. The various biochemical activities of Rep helicase will be highlighted. To carry out the replication function, Rep collaborates with multiple host factors. Rep interacts with PCNA, RPA-32 to replicate MYMIV-DNA ‘A’ component. In order to facilitate studies on host factors, we have also developed a yeast model of IMYMV-Bg DNA replication. Currently this model system is being dissected with regard to its mode and efficiency of operation. We have also engineered the viral DNA to develop a suitable RNAi vector to knock down the host genes of interest.
