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Title: The Bean pod mottle virus RNA2-encoded 58-kilodalton protein P58 is required in cis for RNA2 accumulation

item LIN, JUNYAN - The Ohio State University
item GIO, JIANGBO - The Ohio State University
item FINER, JOHN - The Ohio State University
item DORRANCE, ANNE - The Ohio State University
item Redinbaugh, Margaret
item QU, FENG - The Ohio State University

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2014
Publication Date: 3/1/2014
Citation: Lin, J., Gio, J., Finer, J., Dorrance, A., Redinbaugh, M.G., Qu, F. 2014. The Bean pod mottle virus RNA2-encoded 58-kilodalton protein P58 is required in cis for RNA2 accumulation. Journal of Virology. 88(6):3213-3222.

Interpretive Summary: Bean pod mottle virus (BPMV) is one of the most important pathogens of the U.S. soybean crop, and soybeans with strong natural resistance for controlling the virus disease have yet to be identified. In addition, we still do not understand how the virus replicates in the plant, further hindering the development of knowledge-based control measures. BPMV is an RNA virus, who's genomic RNA is divided into two segments, RNA1 and RNA2. In this study, we examined the replication strategy for the BPMV RNA2. Our results demonstrated an essential role for P58, one of the proteins encoded on RNA2, in the RNA2 replication process. This is interesting, because it means that P58 has a critical function in the replication of the RNA from which it is translated, or made. Because replication of the RNA2 is required for BPMV to cause disease in soybean, our results indicate that P58 provides a potential target for controlling the virus disease.

Technical Abstract: Bean pod mottle virus (BPMV) is a bipartite, positive sense (+) RNA plant virus in the Secoviridae family. Its RNA1 encodes proteins required for genome replication, whereas RNA2 primarily encodes proteins needed for virion assembly and cell-to-cell movement. However, the function of a 58 kilo-dalton protein (P58) encoded by RNA2 has not been resolved. P58 and the movement protein (MP) of BPMV are two largely identical proteins differing only at their N-termini, with P58 extending MP upstream by 102 amino acid residues. In this report, we unveiled a unique role for P58. We show that BPMV RNA2 accumulation in infected cells was abolished when the start codon of P58 was eliminated. The role of P58 does not require the region shared by MP as RNA2 accumulation in individual cells remained robust even when most of the MP coding sequence was removed. Importantly, the function of P58 required the P58 protein, rather than its coding RNA, as compensatory mutants could be isolated that restored RNA2 accumulation by acquiring new start codons upstream of the original one. Most strikingly, loss of P58 function could not be complemented by P58 provided in trans, suggesting that P58 functions in cis to selectively promote the accumulation of RNA2 copies that encode a functional P58. Finally, we found that all RNA1-encoded proteins are cis-acting relative to RNA1. Together, our results suggest that P58 probably functions by recruiting RNA1-encoded polyprotein to RNA2 to enable RNA2 reproduction.