title: Identification of amino acid residues of the coat protein of Sri Lankan cassava mosaic virus affecting symptom production and viral titer in Nicotiana benthamiana.
abstract: Sri Lankan cassava mosaic virus (SLCMV) is bipartite begomovirus infecting cassava in India and Sri Lanka. Interestingly, the DNA-A component of the SLCMV alone is able to infect Nicotiana benthamiana causing symptoms of upward leaf rolling and stunting. One of the differences between monopartite and bipartite begomoviruses is the requirement of Coat Protein (CP) for infectivity; CP being essential for the former, but dispensable in the latter. This investigation was aimed to determine the importance of CP in the infectivity of the bipartite SLCMV, behaving as a monopartite virus in N. benthamiana. We tested CP-null mutants, single amino acid replacement mutants and double, triple and quadruple combinations of the above in SLCMV DNA-A, for infectivity, symptom development and viral DNA accumulation in N. benthamiana. While CP-null mutants were non-infectious, a majority of the single amino acid replacement mutants and their combinations retained infectivity, some with attenuated symptoms and reduced viral titers. Some of the combined mutations restored the attenuated symptoms to wild type levels. Some of the mutations were predicted to cause changes in the secondary structure of the CP, which roughly correlated with the attenuation of symptoms and the reduction in viral titers.
authors.affiliation: University of Delhi South Campus, Department of Plant Molecular Biology, New Delhi 110021, India.
authors.forename: Vaishali
authors.initials: V
authors.lastname: Kelkar
authors.affiliation: University of Delhi South Campus, Department of Plant Molecular Biology, New Delhi 110021, India.
authors.forename: Akhilesh Kumar
authors.initials: AK
authors.lastname: Kushawaha
authors.affiliation: University of Delhi South Campus, Department of Plant Molecular Biology, New Delhi 110021, India. Electronic address: indranil58@yahoo.co.in.
authors.forename: Indranil
authors.initials: I
authors.lastname: Dasgupta
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000502:physiology; D053839:Begomovirus / Q000737:chemistry / Q000235:genetics / Q000472:pathogenicity*; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D010935:Plant Diseases / Q000821:virology*; D014026:Nicotiana / Q000821:virology*; D019562:Viral Load
chemical_list: D000596:Amino Acids; D036022:Capsid Proteins
keywords: Cassava; Coat protein; Infectivity; Mutations; Real time PCR; Symptoms; Tobacco; Viral titer