Rice black-streaked dwarf virus is transmitted by small brown planthoppers, which causes maize rough dwarf disease and rice black-streaked dwarf disease. This virus leads to slow growth or death of the host plants. During the co-evolutionary arms race between viruses and plants, virus-derived small interfering RNAs challenge the plant's defense response and inhibit host immunity through the RNA silencing system. However, it is currently unknown if rice black-streaked dwarf virus can produce the same small interfering RNAs to mediate the RNA silencing in different infected species. In this study, four small RNA libraries and four degradome libraries were constructed by extracting total RNAs from the leaves of the maize (Zea mays) inbred line B73 and japonica rice (Oryza sativa) variety Nipponbare exposed to feeding by viruliferous and non-viruliferous small brown planthoppers. We analyzed the characteristics of small RNAs and explored virus-derived small interfering RNAs in small RNA libraries through high-throughput sequencing. On analyzing the characteristics of small RNA, we noted that the size distributions of small RNAs were mainly 24-nt (19.74%-62.00%), whereas those of virus-derived small interfering RNAs were mostly 21-nt (41.06%-41.87%) and 22-nt (39.72%-42.26%). The 5'-terminal nucleotides of virus-derived small interfering RNAs tended to be adenine or uracil. Exploring the distribution of virus-derived small interfering RNAs hot spots on the viral genome segments revealed that the frequency of hot spots in B73 was higher than those in Nipponbare. Meanwhile, hotspots in the S9 and S10 virus genome segments were distributed similarly in both hosts. In addition, the target genes of small RNA were explored by degradome sequencing. Analyses of the regulatory pathway of these target genes unveiled that viral infection affected the ribosome-related target genes in maize and target genes in metabolism and biosynthesis pathways in rice. Here, 562 and 703 virus-derived small interfering RNAs were separately obtained in maize and rice, and 73 virus-derived small interfering RNAs named as co-vsiRNAs were detected in both hosts. Stem-loop PCR and RT-qPCR confirmed that co-vsiRNA 3.1 and co-vsiRNA 3.5 derived from genome segment S3 simultaneously play a role in maize and rice and inhibited host gene expression. The study revealed that rice black-streaked dwarf virus can produce the same small interfering RNAs in different species and provides a new direction for developing the new antiviral strategies.
Keywords: RBSDV; maize; rice; vsiRNA.