Sequencing compatible primers

For each sample, 100 mg of the ground powder was used for sRNA extraction as previously described (Wang C. et al., 2011 (link)). Six micro-grams (μg) of total RNA were spiked with 5′ ³²P-labeled radioisotope-labeled 19–24 nt RNA oligos and then resolved in 15% urea-PAGE. sRNA library was constructed as previously described (Zhang et al., 2016 (link)). Briefly, sRNAs of 19–24 nt were gel-purified and ligated to a pair of adapters at the 5′ and 3′ ends by using T4 RNA ligase. sRNAs with adapters were transcribed into cDNA and amplified by Illumina sequencing-compatible primers. The final PCR products were sequenced at Texas A&M sequencing center. The sequences of 3′ and 5′ adapters, primers for amplification of the cDNA libraries are listed in Table S1.