Gene expression and population polymorphism of maize Iranian mosaic virus in Zea mays, and intracellular localization and interactions of viral N, P, and M proteins in Nicotiana benthamiana

Abstract

Maize Iranian mosaic virus (MIMV; Mononegavirales, Rhabdoviridae, Nucleorhabdovirus) infects maize and several other poaceous plants. MIMV encodes six proteins, i.e., nucleocapsid protein (N), polymerase cofactor phosphoprotein (P), putative movement protein (P3), matrix protein (M), glycoprotein (G), and large RNA-dependent RNA polymerase (L). In the present study, MIMV gene expression and genetic polymorphism of an MIMV population in maize were determined. N, P, P3, and M protein genes were more highly expressed than the 5' terminal G and L genes. Twelve single nucleotide polymorphisms were identified across the genome within a MIMV population in maize from RNA-Seq read data pooled from three infected plants indicating genomic variations of potential importance to evolution of the virus. MIMV N, P, and M proteins that are known to be involved in rhabdovirus replication and transcription were characterized as to their intracellular localization and interactions. N protein accumulated exclusively in the nucleus and interacted with itself and with P protein. P protein accumulated in both the nucleus and cell periphery and interacted with itself, N and M proteins in the nucleus. M protein was localized in the cell periphery and on endomembranes, and interacted with P protein in the nucleus. MIMV proteins show a distinctive combination of intracellular localizations and interactions.

Keywords: Maize rhabdovirus; Population polymorphism; Protein–protein interactions; Viral gene expression.