Total RNAs were extracted from inflorescence tissues using TRIzol reagent (Invitrogen, USA) following standard protocols.For "conventional sRNA-seq" library, total RNA was seperated in 16% denaturing PAGE gel to excise 18-30 nt, and gel purified RNA was treated by NaCl solution; For "NaIO4 treatment" library, total RNA was seperated in 16% denaturing PAGE gel to excise 18-30 nt, and gel purified RNA was treated by NaIO4 solution; For "PBA-PAGE" library, total RNA was seperated in 16% denaturing PAGE gel supplemented with 2% PBA to excise 18-30 nt, and gel purified RNA was treated by NaCl solution; For"TRM-sRNA-seq"library, total RNA was seperated in 16% denaturing PAGE gel supplemented with 2% PBA to excise 18-30 nt, and gel purified RNA was treated by NaIO4 solution. For AGO1-RIP samples，protein was extracted from Col-0 inflorescence. After  immunoprecipitation, AGO1-bound RNAs were isolated by phenol-chloroform extraction and ethanol precipitation. All types of small RNA libraries were constructed using the NEBNext Multiplex Small RNA Library Prep Set for Illumina (NEB, USA) following manufacturer's instructions and purified using Monarch PCR & DNA kit (NEB, USA).