Abstract
Short interfering RNA (siRNA) has two distinct functions. First, siRNA induces degradation of homologous RNA sequences, termed RNA interference (RNAi) or RNA silencing, in the cytoplasm. Second, siRNA induces epigenetic changes, such as DNA methylation and histone modification, and probably chromatin-based silencing of homologous DNA sequences in the nucleus. But the relationship of dsRNA triggered silencing and epigenetic effects is poorly understood. Here, we designed IR constructs of unique 3' UTRs and promoters derived from the highly conserved rice OsRac gene family, and transformed them into rice. Each of the seven members of the OsRac gene family was specifically suppressed by its respective unique 3' UTRs derived IR construct in transgenic rice. On the other hand, promoter targeted constructs induced de novo DNA methylation, but not silencing. These results suggest that siRNA derived from IR constructs was not sufficient for the induction of the chromatin-based silencing when endogenes are targeted.
