Small RNA-based interactions between rice and the viruses which cause the tungro disease.

Rice tungro disease is caused by a complex of two viruses, Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV). To examine the RNAi-based defence response in rice during tungro disease, we characterized the virus-derived small RNAs and miRNAs by Deep Sequencing. We found that, while 21 nt/22 nt (nucleotide) siRNAs are predominantly produced in a continuous, overlapping and asymmetrical manner from RTBV, siRNA accumulation from RTSV were negligible. Additionally, 54 previously known miRNAs from rice, predicted to be regulating genes involved in plant defence, hormone signaling and developmental pathways were differentially expressed in the infected samples, compared to the healthy ones. This is the first study of sRNA profile of tungro virus complex from infected rice plants. The biased response of the host antiviral machinery against the two viruses and the differentially-expressed miRNAs are novel observations, which entail further studies.