The Agrobacterium tumefaciens Ti Plasmid Virulence Gene virE2 Reduces Sri Lankan Cassava Mosaic Virus Infection in Transgenic Nicotiana benthamiana Plants

Cassava mosaic disease is a major constraint to cassava cultivation worldwide. In India, the disease is caused by Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV). The Agrobacterium Ti plasmid virulence gene virE2, encoding a nuclear-localized, single-stranded DNA binding protein, was introduced into Nicotiana benthamiana to develop tolerance against SLCMV. Leaf discs of transgenic N. benthamiana plants, harboring the virE2 gene, complemented a virE2 mutation in A. tumefaciens and produced tumours. Three tested virE2 transgenic plants displayed reduction in disease symptoms upon agroinoculation with SLCMV DNA A and DNA B partial dimers. A pronounced reduction in viral DNA accumulation was observed in all three virE2 transgenic plants. Thus, virE2 is an effective candidate gene to develop tolerance against the cassava mosaic disease and possibly other DNA virus diseases.