title: RNA denovo:Platycodon grandiflorus
design: After RNA Purification and reverse transcription, DNA ends were flattened and phosphorylated at 5 'end. A "a" was formed at 3' end, and then a bubble like joint with protruding "t" at 3 'end was connected. PCR and PCR products were thermally denatured into single strand, and then a single stranded circular DNA library was obtained by cyclization of single strand DNA with a bridge primer