sRNA-seq of Embryo of maize B73
Total RNA (10 μg) from each sample was extracted using the RNeasy Mini Kit (Qiagen) according to the manufacturer’s protocol. Novex 15% TBE-Urea gel (Invitrogen) was used to isolate small RNA fragments (30 nt in length) from total RNA. The purified small RNAs were ligated to a 5’ adaptor (Illumina) and the ligation products were purified in Novex 15% TBE-Urea gels. Next, a 3’ adaptor (Illumina) was ligated to the 5’ ligation products and further purified in a Novex 10% TBE-Urea gel (Invitrogen). Reverse transcriptase PCR was used to reverse transcribe these ligation products. Then, a 6% TBE-Urea gel (Invitrogen) was used to purify the amplification products. The DNA fragments were purified, quantified and then sequenced for 36 cycles using the protocol provided by Illumina.