miRNA sequencing of Glycine max
We used the Trizol reagent (Invitrogen Life Technologies) to extract RNA. Then we used a NanoDrop spectrophotometer (Thermo Scientific) to measure concentration, mass, and integrity.  According to the instructions, we constructed a small RNA library using the NEBNext multiplex small RNA library preparation set for Illumina (New England Biolabs, Inc.). In summary, we used a ligase mixture to 1g of total RNA from soybean root samples (CK1, T1, CK4, T4, respectively), which was connected to the 3 'and 5' adapters. The obtained samples were reverse transcribed (Superscript II reverse transcriptase). We conducted PCR product amplification. We used the Bioanalyzer 2100 system (Agilent) and NovaSeq 6004 platform (Illumina) to quantify and sequence the sequencing library.