ARS | Publication request: Soybean mosaic virus infection and helper component-protease enhance accumulation of Bean pod mottle virus-specific siRNAs

Submitted to: Plant Pathology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 22, 2011
Publication Date: December 1, 2011
Citation: Lim, H., Jang, C., Kim, H., Kim, J., Lee, C., Hong, J., Ju, H., Domier, L.L. 2011. Soybean mosaic virus infection and helper component-protease enhance accumulation of Bean pod mottle virus-specific siRNAs. Plant Pathology Journal . 27(4):315-323.

Interpretive Summary: Bean pod mottle virus (BPMV) is one of the most widespread and damaging viruses infecting soybeans in the Midwestern United States. Soybean plants infected with BPMV often develop symptoms that are initially severe, but decrease in severity over time. This type of symptom recovery is associated with degradation of the virus RNA chromosomes by plant antiviral defenses. In this study, changes in the accumulation of BPMV RNAs were investigated in soybean plants infected with BPMV alone, or infected with both BPMV and Soybean mosaic virus (SMV) and in transgenic soybean plants expressing an SMV protein that interferes with antiviral defenses. The results showed that SMV and the single SMV protein prevented plants infected with BPMV from degrading BPMV RNAs and further suggested that the SMV protein interfered with the activity of specific plant enzymes that are involved in reducing injury from virus infection. This information will be of interest to scientists studying the interactions between plants and viruses that determine disease severity.

Technical Abstract: Soybean plants infected with Bean pod mottle virus (BPMV) develop acute symptoms that usually decrease in severity over time. In other plant-virus interactions, this type of symptom recovery has been associated with degradation of viral RNAs by post-transcriptional gene silencing (PTGS), which is accompanied by the accumulation of virus-derived small interfering RNAs (siRNAs). In this study, changes in the accumulation of BPMV siRNAs were investigated in soybean plants infected with BPMV alone, or infected with both BPMV and Soybean mosaic virus (SMV) and in transgenic soybean plants expressing SMV helper component-protease (HC-Pro). Potyviral HC-Pros are potent suppressors of PTGS that enhance the accumulation of heterologous viruses. In plants infected with BPMV alone, accumulation of siRNAs was positively correlated with symptom severity and accumulation of BPMV genomic RNAs. Plants infected with both BPMV and SMV and BPMV-infected transgenic soybean plants expressing SMV HC-Pro exhibited severe symptoms characteristic of BPMV-SMV synergism, and showed enhanced accumulation of BPMV RNAs and siRNAs compared to plants infected with BPMV alone and nontransgenic plants. Likewise, SMV HC-Pro enhanced the accumulation of siRNAs produced from a silenced green fluorescent protein gene in transient expression assays, while the P19silencing suppressor of Tomato bushy stunt virus did not. These studies showed that SMV HC-Pro interfered with the activity of RNA-induced silencing complexes, but not the activity of Dicer-like enzymes in antiviral responses in soybean.