5’-RACE
The 5’modified RACE was performed using the FirstChoice RLM-RACE Kit (Invitrogen). In brief, total RNA was isolated from young leaves ofB. napus . Then, 8–10 µg high-quality total RNA (A260/280≈2.00) was directly ligated to the 5′-RACE adapter without calf intestinal phosphatase and tobacco acid pyrophosphatase treatment. The first-strand cDNA was synthesized using M-MLV reverse transcriptase according to the manufacturer’s instructions. The PCR amplification was performed using the 5′ outer primer and gene-specific outer primer, and 0.1 µL PCR product was used as the template for nested PCR. Nested PCR amplification was performed using the 5′ inner primer and gene-specific inner primer. The PCR products were gel-purified and then cloned and sequenced.