1Department of Plant Molecular Biology, University of Delhi South Campus, India.
2Department of Disease and Stress Biology, John Innes Centre, Norwich, United Kingdom.
Abstracts of Research Papers Presented during the National Symposium of Indian Virological Society at Unit of Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110 012, October 14–1.
Cassava, Manihot esculenta Crantz, is cultivated for its starch containing tuberous roots and represents an important source of dietary calories. Cassava mosaic disease (CMD) is widespread in Africa and the Indian subcontinent and represents one of the major constraints in the cultivation of this important crop.
Indian cassava mosaic virus (ICMV) is the only begomovirus thought to be the causal agent of CMD in India. As a first step towards assessing the variability of cassava infecting geminiviruses (CIGs) from India, full-length, biologically competent clones were obtained using PCR-based cloning strategy. Our study led to the identification of a second begomovirus, Sri Lankan cassava mosaic virus (SLCMV), a CIG reported only from Sri Lanka, associated with mosaic disease cassava plants. The infectious nature of the cloned components was demonstrated on both Nicotiana benthamiana and the original host cassava.
In order to gain an insight into the virus movement process, the behaviour of BC1, AV2 andAC4 was investigated by fluorescently tagging these proteins with the green fluorescent protein (GFP) and transiently expressing them in detached N. benthamiana leaves, following biolistic inoculation. Intracellular localization of the tagged reporter molecule in such bombarded leaves was observed using a fluorescence microscope. BC1 exhibited peripheral localization in bombarded cells; although in certain cases punctate, fluorescent specks could be seen in apposition to the cell wall. Deletion analysis of BC1 led to the identification of an intensely hydrophobic stretch of approximately hundred, centrally located amino acid residues responsible for peripheral targeting of the protein. No movement of the BC1 protein to the neighbouring cells could be observed. TheAV2 andAC4 displayed perinuclear as well as peripheral localization, reminiscent of the behaviour of BC1, although in the case of AV2 fluorescence could be seen to spread to the adjacent cells. The observations indicate a potential role of these proteins in aiding virus movement.
