Characterization of maize translational responses to sugarcane mosaic virus infection

Sugarcane mosaic virus (SCMV) frequently causes dramatic losses in maize production as the main pathogen of maize dwarf mosaic disease. It is important to understand the translational responses in maize to SCMV infection since viruses have to recruit host translation apparatus to express their proteins. However, due to technical limitations, research on virus translation lags far behind that on transcription. Here, we studied the relationship between systemic symptom expression and virus accumulation and found that both SCMV RNA and proteins accumulated rapidly during the systemic infection process in which varying degrees of chlorosis to mosaic symptoms developed on non-inoculated leaves. In addition, we applied ribosome profiling, which couples polysomal mRNA isolation with high-throughput sequencing, on the symptomatic leaves infected with SCMV to unravel the translational responses of maize to viral infection on a genome-wide scale. The results showed that only the genomic positive-stranded RNA of SCMV was involved in translation, and SCMV only occupied a small amount of translational resources of host plant at the early stage of infection. Further analyses on a global gene expression and gene ontology (GO) enrichment revealed that photosynthesis and metabolism were dramatically repressed at both transcriptional and translational levels. Altogether, our results laid a foundation for dissecting the molecular mechanism of plant translational responses to viral infection.