Transcriptome analysis of alfalfa under cold and freezing stress
The samples from three treatments (Control, Cold and Freezing) were subjected to extract small RNA using TRIzol method (Invitrogen, CA, USA) according to the manufacturer’s instructions. Small RNAs were ligated sequentially to 5’ and 3’ RNA/DNA chimeric oligo-nucleotide adaptors, and the resulting ligation products were gel purified by 15% denaturing PAGE and reverse-transcribed to produce cDNAs. The cDNAs were sequenced using a Genome Analyzer IIx System as protocol described (BGI-Shenzhen Co. Ltd., Shenzhen, China).