ORF43 of maize rayado fino virus is dispensable for systemic infection of maize and transmission by leafhoppers

Abstract

Maize rayado fino virus (MRFV) possesses an open reading frame (ORF43) predicted to encode a 43 kDa protein (p43) that has been postulated to be a viral movement protein. Using a clone of MRFV (pMRFV-US) from which infectious RNA can be produced, point mutations were introduced to either prevent initiation from three potential AUG initiation codons near the 5'-end of ORF43 or prematurely terminate translation of ORF43. Inoculation of maize seed via vascular puncture inoculation (VPI) resulted in plants exhibiting symptoms typical of MRFV infection for all mutants tested. Furthermore, corn leafhoppers (Dalbulus maidis) transmitted the virus mutants to healthy plants at a frequency similar to that for wild-type MRFV-US. Viral RNA recovered from plants infected with mutants both prior to and after leafhopper transmission retained mutations blocking ORF43 expression. The results indicate that ORF43 of MRFV is dispensable for both systemic infection of maize and transmission by leafhoppers.

Engineering Maize rayado fino virus for virus‐induced gene silencing

“…Notably, a second small overlapping open reading frame not found in OBDV is found in the 3' end in Citrus sudden death-associated virus, another member of the genus (Maccheroni et al, 2005). Similarly, a second small overlapping open reading frame absent in OBDV is found in the 5' end in MRFV, in which it encodes a P43 protein of unknown function that is not required for systemic movement or leafhopper transmission (Edwards, Weiland, Todd, Stewart, & Lu, 2016). Characterization of newly reported marafivirus species may shed more insights into the extent of the diversity of genome expression strategies within the Marafivirus genus.…”

Transcriptome of the Maize Leafhopper ( Dalbulus maidis ) and Its Transcriptional Response to Maize Rayado Fino Virus (MRFV), Which It Transmits in a Persistent, Propagative Manner

“…MRFV genomic RNA can serve as mRNA for viral replication proteins required for viral RNA replication and is sufficient to launch infection in inoculated plants ( 2 , 3 ). Translation of viral proteins requires host ribosomes (reviewed in reference 4 ).…”

“…MRFV is transmitted by D. maidis in a persistent, propagative manner. After leafhopper acquisition of MRFV, a latent period of at least 1 week must elapse before leafhoppers become capable of transmitting the virus to new plants ( 2 , 3 ). During the latent period, MRFV is thought to replicate within the insect and cross several molecular and/or physical barriers before it can be transmitted to plants, similar to other persistent, propagatively transmitted viruses (see review [ 4 ]).…”

“…From the transcriptome, we identified genes in D. maidis which are likely to be involved in insect immune responses, including components of Toll, Imd, Jak/Stat, other immune signaling pathways, the prophenoloxidase-activating system, the melanization pathway ( 9 , 27 ), and RNAi-associated genes and pathways. Further, we examined the transcriptome response of D. maidis to feeding on MRFV-infected maize, which the leafhopper persistently and propagatively transmits, shortly after exposure (4 h) and in response to active virus replication at the end of the latent period (7 days) (see references 2 , 3 , and 28 ). Genes highly regulated in response to MRFV exposure were identified and compared with those identified in other hopper vector-virus systems.…”

Identification and full genome analysis of the first putative virus of sea buckthorn (Hippophae rhamnoidesL.)

“…It is a proline-, serine-, and threonine-rich protein, and was shown to be dispensable for the ability to infect maize and leafhopper transmissibility in the MRFV translation mutant experiments. Moreover, unambiguous evidence that the MRFV ORF43 is expressed in vivo is lacking [95]. The absence of MP gene could be the result of marafivirus phloem limitation [38].…”