1Plant Molecular Biology, International Centre for Genetic Engineering Biotechnology, New Delhi-110067, India.
2Plant breeding and biotechnology laboratory, Department of Botany, University of Dhaka, Bangladesh.
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.
Most plant viruses are initiators and targets of host defence mechanism, viz., RNA silencing. During the course of evolution as a means of counter-defence strategy most of the viruses have been found to encode proteins that suppress this adaptive host defense. Both RNA viruses as well DNA viruses have been found to encode suppressor molecules. The suppressors from different viruses generally vary in their sequence as well mechanism of action. Potent phytopathogen, Mungbean yellow mosaic India virus (MYMIV), encodes AC2 protein (also known as AL2, C2 and transcriptional activator protein) that has been shown to suppress RNA silencing. On agroinfiltration of AC2 in the GFP silenced line, reversion of silencing and expression of GFP has been observed under U.V. This reversion was concomitant with an increase in the GFP mRNA level and decrease in GFP siRNA level. Data would be presented to show that the AC2 exerts its suppression effect both at the initiation as well at the systemic spread of silencing. AC2 is a 136 amino acid long protein that served as a transcriptional activator in yeast monohybrid assay. However, the transactivation property is lost on truncation of the acid blob (deletion of 110–136 aa) located at the C-terminal of the protein. The functional characterization of a viral suppressor is extremely valuable as the suppressors can serve as a tool to elucidate the intricacies of RNA silencing pathway, to construct transgenic as better biofermenter and more significantly in devising the viral control strategies.
