library_construction_protocol: RNA was extracted using Qiagen RNeasy Kit Total RNA Sample QC: Agilent 2100 Bio analyzer (Agilent RNA 6000 Nano Kit). Purification:  mRNA polyA molecules using poly-T oligo-attached magnetic beads. Fragmentation: mRNA is fragmented into small pieces using divalent cations under elevated temperature. The cleaved RNA fragments are copied into first strand cDNA using reverse transcriptase and random primers. This is followed by second strand cDNA synthesis using DNA Polymerase I and RNase H. These cDNA fragments then have the addition of a single 'A' base and subsequent ligation of the adapter. The products are then purified and enriched with PCR amplification. PCR yield quantified by Qubit and pooled samples together to make a single strand DNA circle (ssDNA circle), which gave the final library. DNA nanoballs (DNBs) were generated with the ssDNA circle by rolling circle replication (RCR) to enlarge the fluorescent signals at the sequencing process.  100bp PE sequencing: BGISEQ 500 platform