In plants,all known small RNAs(sRNAs)are processed by Dicer-like proteins(DCLs).In this study,we explored the possibility that plants produce sRNAs independent of DCLs.We profiled sRNAs in an Arabidopsis dcl quadruple mutant and identified a class of DCL-independent sRNAs(DI-sRNAs).DI-sRNAs have a broader size distribution,mainly ranging from 20-60 nt.Vast majority of the DI-sRNAs are derived from transposons and other repetitive sequences,most of which are targets of RNA-directed DNA methylation(RdDM).DI-sRNAs are associated with AGO4 and guide AGO4 to homologous sequences to direct DNA methylation.Intriguingly,some DI-sRNAs appear as ladders in size,with identical 5ends but different 3ends,suggesting that DI-sRNAs are processed through 3-5 trimming of AGO4-bound precursor transcripts.These data indicate that Arabidopsis can produce sRNAs in a DCL-indepenent manner.We propose that DI-sRNAs may serve as the primal signal for the establishment of RdDM.