Stem
Total RNA was extracted from collected tissues using the RNAprep pure plant kit (TIANGEN, China). Qualified RNA per sample was used to generate sequencing libraries by NEBNext Ultr RNA Library Prep Kit for Illumina (NEB, USA) following manufacturer's instruction. mRNA was purified from total RNA using poly-T oligo-attached magnetic beads, then interrupted into short fragments which were used as templates for cDNA synthesis. After purification, reparation, adenylation and adapter ligation of 3'end, 150200 bp of cDNA fragments were separated for PCR amplification. At last, the libraries were quality control by Agilent 2100 Bioanalyzer and Q-PCR.