Synergistic infection of two viruses MCMV and SCMV increases the accumulations of both MCMV and MCMV-derived siRNAs in maize.

The co-infection of Maize chlorotic mottle virus (MCMV) and Sugarcane mosaic virus (SCMV) can cause maize lethal necrosis. However, the mechanism underlying the synergistic interaction between these two viruses remains elusive. In this study, we found that the co-infection of MCMV and SCMV increased the accumulation of MCMV. Moreover, the profiles of virus-derived siRNAs (vsiRNAs) from MCMV and SCMV in single- and co-infected maize plants were obtained by high-throughput sequencing. Our data showed that synergistic infection of MCMV and SCMV increased remarkably the accumulation of vsiRNAs from MCMV, which were mainly 22 and 21 nucleotides in length. The single-nucleotide resolution maps of vsiRNAs revealed that vsiRNAs were almost continuously but heterogeneously distributed throughout MCMV and SCMV genomic RNAs, respectively. Moreover, we predicted and annotated dozens of host transcript genes targeted by vsiRNAs. Our results also showed that maize DCLs and several AGOs RNAs were differentially accumulated in maize plants with different treatments (mock, single or double inoculations), which were associated with the accumulation of vsiRNAs. Our findings suggested possible roles of vsiRNAs in the synergistic interaction of MCMV and SCMV in maize plants.