Maize Iranian mosaic virus shows a descending transcript accumulation order in plant and insect hosts

Maize Iranian mosaic virus (family Rhabdoviridae) improves biological traits of its vector Laodelphax striatellus

Plant viruses can alter the behavior or performance of their arthropod vectors, either indirectly (through effects of virus infection on the host plant) or directly (from virus acquisition by the vector). Given the diversity of plant viruses and their arthropod vectors, the effects for any specific system are not possible to predict. Here, we present experimental evidence that acquisition of maize Iranian mosaic virus (MIMV, genus Nucleorhabdovirus, family Rhabdoviridae) modifies the biological traits of its insect vector, the small brown planthopper (SBPH) Laodelphax striatellus. MIMV is an economically important virus of maize and several other grass species. It is transmitted by SBPHs in a persistent-propagative manner. We evaluated the effects of MIMV acquisition by SBPH on its life history when reared on healthy barley plants (Hordeum vulgare). We conclude that 1) MIMV acquisition by SBPHs increases female fecundity, duration of the nymph stage, adult longevity, and survival of SBPHs, (2) the mortality rate and female-to-male sex ratio are reduced in MIMV-infected planthoppers, and (3) MIMV infection increases the concentration of some biochemical components of the infected plants, including carbohydrates, some amino acids, and total protein, which might influence the life traits of its insect vector. The results indicate the potential of MIMV to improve the ecological fitness of its vector, SBPH, through direct or indirect effects, with the potential to increase the spread of the virus.

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

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.