Vol.:(0123456789) 1 3 Archives of Virology https://doi.org/10.1007/s00705-017-3680-y ORIGINAL ARTICLE Maize Iranian mosaic virus shows a descending transcript accumulation order in plant and insect hosts Mozhgan Hortamani 1  · Amir Massah 1  · Keramat Izadpanah 2 Received: 21 September 2017 / Accepted: 5 December 2017 © Springer-Verlag GmbH Austria, part of Springer Nature 2017 Abstract Maize Iranian mosaic virus (MIMV) is a distinct member of the genus Nucleorhabdovirus. In this study, expression of all MIMV genes in maize for four weeks after inoculation and in inoculative planthoppers was examined using a quantitative RT-PCR (RT-qPCR) assay. Accumulation of MIMV P, gene 3, M, G and L transcripts relative to N transcripts was meas- ured and normalized to 18S rRNA in maize plants and to the ribosomal protein S13 gene (RPS13) in planthoppers using the comparative C T method. In plants, higher levels of MIMV N transcripts were found relative to other transcripts, while MIMV L transcripts were at the lowest levels. The highest accumulation of MIMV transcripts was found at 14 days post- inoculation (dpi). At 21 dpi, we found the lowest transcript levels for all genes, which increased again at 28 dpi, although in lower amounts than at 14 dpi. In Laodelphax striatellus, MIMV M, G and L transcripts accumulated at lower levels than other transcripts. The gene 3 transcript level was high in both plants and planthoppers. Our results showed that transcript accumulation for the MIMV genes was similar in both hosts and followed the pattern of sequential transcriptional attenua- tion from the 3ˊ to the 5ˊ end of the genome, similar to vertebrate rhabdoviruses. These results indicate that the regulation of virus gene transcription for this plant-infecting rhabdovirus is similar to that of some vertebrate-infecting rhabdoviruses. Introduction Maize Iranian mosaic virus (MIMV), a member of the genus Nucleorhabdovirus of the family Rhabdoviridae, causes eco- nomic losses in maize production in Iran [22]. The lack of a serological relationship between MIMV and maize mosaic virus (MMV, genus Nucleorhabdovirus) and diferences in the sizes of proteins, particle size, host range, natural vectors, and sequence suggest that MIMV is a distinct virus [12, 20, 29]. The virus is transmitted in a persistent-propagative manner by the planthoppers Laodelphax striatellus and Unkanodes tanasijevici [21]. Transovarial transmission in L. striatellus has been reported [30]. It has been proposed that rhabdovi- ruses evolved from an ancestral insect virus, because they are able to infect arthropods extensively without lethal efect, they undergo transovarial transmission in insects, and they are not transmitted through seed in plants [32]. The MIMV genome is an unsegmented negative-sense RNA that encodes six distinct genes in the order 3’-N-P-gene 3-M-G-L-5’, and as in other rhabdoviruses, each gene contains a coding region fanked by noncoding regions that are bordered by transcription initiation signals and transcription termination polyadenylation signals [29]. In rhabdoviruses, the nucleocapsid (N) protein encapsi- dates the genomic RNA and is a component of the polymerase complex and the viroplasm. The N protein of nucleorhabdovi- ruses has two amino acid sequence motifs that are related to nucleoplasmin-like nuclear localization signals (NLS) and are predicted to be required for its nuclear localization. The phosphoprotein (P) is another component of the polymerase complex and a part of viral nucleocapsid core. The P protein is suggested to have a role in the suppression of host antivi- ral defenses [27]. In addition, rice yellow stunt virus P6 also suppresses RNA silencing in systemic leaves [15]. The pro- tein encoded by the third gene in rhabdoviruses seems to act as movement protein and has a predicted structure similar to those of members of the 30 K superfamily of plant virus move- ment proteins [17, 26, 31, 38]. Among known rhabdoviruses, this protein is encoded only by plant rhabdoviruses. The matrix protein (M) condenses the nucleocapsid and associates with Handling Editor: Ralf Georg Dietzgen. * Amir Massah amassah@cc.iut.ac.ir 1 Department of Plant Protection, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran 2 Department of Plant Protection, College of Agriculture, Shiraz University, Shiraz 71441-65186, Iran