Differential disease symptoms and full-length genome sequence analysis for three strains of Tobacco etch virus

摘要

Tobacco etch virus (TEV) strains HAT, Mex21, and N have been the focus of numerous studies to dissect a host resistance mechanism in Capsicum spp. Little is known, however, about their general pathogenicity and genomic sequence data are not available on the TEV strains Mex21 and N. Four Nicotiana spp. were evaluated after inoculation with each TEV strain. Nicotiana tabacum 'Kentucky 14' and N. clevelandii plants expressed varied systemic symptoms dependent on the TEV strain; however, disease severity increased from HAT (mild mosaic symptoms) to Mex21 (more severe mosaic symptoms with stunting) to N (severe chlorosis and stunting). Nicotiana tabacum 'Samsun' plants developed relatively milder symptoms and N. glutinosa plants remained symptomless, although they were systemically infected. The genome of each TEV strain was sequenced and shown to consist of 9,495 nucleotides and a polyprotein of 3,054 amino acids. Comparison of their nucleotide sequences relative to the original HAT sequence (GenBank Accession No. M11458) revealed 95, 92, and 92 % identity for HAT-AU (from Auburn University), Mex21, and N, respectively. HAT-AU had 91 % sequence identity with Mex21 and N, while Mex21 and N were more closely related with 98 % nucleotide sequence identity. Similarly, the amino acid sequence identities for the full-length polyprotein ranged from 95 % for HAT-AU when compared with N to a high of 98 % identity between Mex21 and N.