Abstract
Endogenous 14-kbp double-stranded RNAs (dsRNAs), which are classified into the Endornaviridae virus family, have been found in japonica rice. Although dsRNAs generally can be substrates for RNaseIII family enzymes as an RNA silencing trigger, the endogenous dsRNAs are detected in every tissue and all stages at a constant copy number. The presence of dsRNAs in several knockdown strains of DCL genes (DCL2, DCL3a) or RDR genes (RDR1-5) was examined in order to clarify the relationship between the maintenance of dsRNAs and the RNA silencing systems. Among these knockdown strains, the dsRNAs were not detected in DCL2 or RDR4 knockdown strains. Therefore, the dsRNAs were re-introduced into these dsRNA-lacking, knockdown strains by reciprocal crosses using dsRNA-carrying plants as donors. Consequently, in several F1 progenies of the DCL2 knockdown strain, the dsRNAs were lost or reduced. Our results suggest that DCL2 might be involved in the maintenance of the rice endogenous dsRNAs.
