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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #387256

Research Project: Molecular Identification, Characterization, and Biology of Foreign and Emerging Viral and Bacterial Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: Coat protein expression strategy of maize rayado fino virus and evidence for requirement of CP1 for leafhopper transmission

item MLOTSHWA, SIZOLWENKOSI - The Ohio State University
item KHATRI, NITIKA - The Ohio State University
item Willie, Kristen
item XU, JUNHUAN - The Ohio State University
item Todd, Jane
item HONG, HONG HANH - The Ohio State University
item Stewart, Lucy

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2022
Publication Date: 5/1/2022
Citation: Mlotshwa, S., Khatri, N., Willie, K.J., Xu, J., Todd, J.C., Hong, H., Stewart, L.R. 2022. Coat protein expression strategy of maize rayado fino virus and evidence for requirement of CP1 for leafhopper transmission. Virology. 507:96-106.

Interpretive Summary: A leafhopper-transmitted corn-infecting virus, maize rayado fino virus (MRFV) impacts production in the southern United States and in Central and South America. Spherical virus particles of MRFV are composed of two carboxy-coterminal coat proteins, one with an N-terminal extension compared to the other, which encapsidate the +ssRNA genome of MRFV in a 1:3 ratio. However, how the two different but overlapping coat proteins are expressed from MRFV, and whether both are essential to the virus infection cycle, was not experimentally determined for MRFV, although similar research was previously conducted for the related oat blue dwarf virus (OBDV). A series of MRFV mutants were designed to disrupt various possible expression modes of MRFV coat proteins 1 and 2 and tested for infection outcomes. Mutations in MRFV that disrupted CP2 expression rendered virus nonviable for whole plant infection, similar to reduced viability of similar mutants of OBDV previously tested in single cells. In contrast to OBDV, expression of CP1 in MRFV by polyprotein release was minimal. Experimental results provided evidence that CP1 is also required for leafhopper transmission of the virus, providing the first experimental information on transmission determination for this group of viruses. Together, these data demonstrate similarities and differences in coat protein expression for MRFV and related viruses, and elucidate key components of the virus lifecycle that may be useful for plant protection from MRFV and for biotechnological applications of MRFV capsid proteins.

Technical Abstract: Marafiviruses, including maize rayado fino virus (MRFV) and oat blue dwarf virus (OBDV), encode two carboxy co-terminal coat proteins, CP1 and CP2, which encapsidate the genome to form icosahedral virions. While CP2 expression is expected to be solely driven from subgenomic RNA under a marafibox promoter sequence, the larger CP1 with an in-frame N-terminal extension relative to CP2 could potentially be expressed either by proteolytic release from the MRFV polyprotein or from subgenomic RNA translation. We examined MRFV CP expression strategy with a series of mutations in the putative polyprotein cleavage site, subgenomic promoter, and CP start codons. In contrast to OBDV, polyprotein expression of CP1 for MRFV was negligible. Mutants depleted in CP1 exhibited systemic infection and formation of virus-like particles, but not leafhopper transmission. CP2 appeared to be essential, as mutants blocking its expression failed to establish system infection.