Comparison of miRNAs in diploid and autotetraploid Paulownia fortunei using high-throughput sequencing
Two sRNA libraries were constructed and sequenced using the GAIIx platform (Illumina, San Diego, CA, USA). Briefly, 4 µg of total RNA were successively ligated with 5’ and 3’ adapters. Reverse transcription was used to create single-stranded cDNA, which was then amplified by 12 cycles of PCR.  A gel purification procedure was carried out to select fragments of 140–160 bp in size, which were used to produce the sRNA libraries for Illumina sequencing.