RNA-Seq of Populus humilis: 2 years old  leaf
RNA was extracted using the RNAeasy kit (Qiagen) as the manufacturer's instructions with the addition of 20 mg PEG8000/mL to the extraction RLC buffer solution and an on-column DNA digestion step with DNAse I (Qiagen). RNA quality was verified by Experion HighSens capillary gels (Bio-Rad). Five total RNA preparations were pooled and amplified using the SMARTer PCR cDNA Synthesis Kit (Clontech) according to the manufacturer's instructions. cDNA libraries were prepared for sequencing using standard  Illumina protocols.