M. Russo, A. De Stradis, D. Boscia, L. Rubino, M.G. Redinbaugh, J.J. Abt, G.P. Martelli
doi: 10.4454/jpp.v90i2.675
This paper reports the complete nucleotide sequence of the genome of Maize white line mosaic virus (MWLMV) and describes the ultrastructural features of infected maize cells. The viral genome is an RNA molecule 4293 nt in size with the same structural organization of members of the Aureusvirus and Tombusvirus genera. It comprises five ORFs flanked by non-coding regions at the 5’ (40 nts) and 3’ (225 nts) ends which encode, in the 5’-3’ direction, proteins with predicted Mr of 30,009 (prereadthrough), 89,140 (readthrough, replication-associated proteins), 35,080 (coat protein), 24,644 (movement protein), and 15,155 (silencing suppressor). Some of ultrastructural features of MWLMV-infected cells, e.g. lobate nuclei, localization of virus particles in tonoplast evaginations bulging into the vacuoles, plentiful occurence of virions and of aggregates of virus coat protein in the cytosol, intramitochondrial patches of electron-dense material, tallied with those reported for a number of members of the family Tombusviridae. However, differences were observed with the cytopathology of the aureusvirus Johnsongrass chlorotic streak mosaic virus (JCSMV) which is the viral species more closely related to MWLMV from the molecular point of view. MWLMV was serologically unrelated to JCSMV, Pothos latent virus (PoLV), the type species of the Aureusvirus genus, and Maize necrotic streak virus (MNeSV), another maize pathogen with similar biological properties, belonging in the family Tombusviridae. In a phylogenetic tree constructed with whole genome sequences, MWLMV clustered with all members of the genus Aureusvirus. Thus, properties and phylogenetic relationships place MWLMV in the genus Aureusvirus. However, molecular differences with all sequenced species of this genus, the lack of serological relationship with PoLV and JCSMV, and the different cytopathology elicited in infected tissues, suggest that MWLMV be regarded as a separate species.