Candidate miRNAs from Oryza sativa for Silencing the Rice Tungro Viruses

Rice tungro disease (RTD), caused by Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV) is one of the most prominent viral diseases in Asian countries. This virus disease problem seems to have been accentuated in those countries by causing a series of outbreaks over the years after being first reported in International Rice Research Institute (IRRI), Philippines, in 1963. One of the effective ways to combat viruses is through RNA silencing. microRNA is an important player in the RNA silencing mechanism. Genome sequences analysis shows RTBV-SP isolate (8 Kb) is composed of four open reading frames (ORF 1, ORF 2, ORF 3, and ORF 4), meanwhile, RTSV-SP (12 Kb) consists of one open reading frame encoded by seven different polyproteins (P1, CP1, CP2, CP3, NTP, Pro, and Rep). Therefore, this study investigated possible rice-encoded miRNAs targeted on RTBV and RTSV using in silico analysis. Five bioinformatics tools were employed using five different prediction algorithms: miRanda, RNA22, RNAhybrid, Tapirhybrid, and psRNATarget. The results revealed each RTBV and RTSV can be silenced by three potentially best candidate rice-encoded miRNA. For RTBV, osa-miR5510 (accession no. MIMAT0022143), osa-miR3980a-3p (accession no. MIMAT0019676), and osa-miR3980b-3p (accession no. MIMAT0019678) are being predicted by all five algorithms. Meanwhile, for RTSV, three miRNAs predicted are osa-miR414 (accession no. MIMAT0001330), osa-miR5505 (accession no. MIMAT00221138) and osa-miR167a-3p (accession no. MIMAT0006780). The predicted data provide useful material for developing RTBV and RTSV-resistant rice varieties.