Molecular Virology Lab, National Botanical Research Institute, Lucknow-226 001, India.
Abstracts of the papers presented at the XVIII National Conference of Indian Virological Society at Post Graduate Institute of Medical Education and Research, Chandigarh, India, December 11–13, 2008.
Cotton leaf curl disease is an important disease of cotton. It is a complex disease induced by Cotton leaf curl virus (CLCuV), satellite β DNA and perhaps nanovirus component. Satellite molecule DNA β associated with CLCuD plays amajor role in symptom induction. To test this hypothesis, Nicotiana tabacum plants were transformed with Agrobacterium tumefaciens containing DNA construct pBI121-βC1 carrying βC1 gene. The T0 transgenic N. tabacum plants displayed abnormal phenotypes, including leaf distortion, upward leaf-curling and blistering of leaves. In addition, abnormal phenotypes such as interveinal protuberances or small interveinal tissue outgrowths could be observed on the undersides of some leaves of transgenic plants. The virus-like phenotype developed by βC1 transgenic plants were more severe than viral symptoms produced in non-transgenic tobacco plants co-infected with CLCuV and CLCuV β. DNA β acts as silencing suppressor, however the RNA silencing pathway targeted by the βC1 proteins remains to be elucidated. In the present study, expression of βC1 gene in tobacco elicited virus-like symptoms in the absence of helper virus suggesting that βC1 protein perhaps play a role in developmental regulation by interfering with miRNA pathways. It may also be speculated that βC1 protein probably affects the activity of the DICER-like proteins in plants during nuclear activities that function in silencing suppression. The other possibility is that this protein could either down regulate transcription of a host protein that acts in the PTGS pathway in the cytoplasm or could activate transcription of a host PTGS inhibitor.
