qRT-PCR Analysis

Genes involved in BR biosynthesis and signal transduction pathway were selected from CarrotDB¹ (Xu, 2014). The primers of each gene were designed via Primer Premier 5.0 software, and were displayed in Table ​Table11. qRT-PCR was performed in a real-time PCR detection system (Bio-Rad, Hercules, CA, United States). The cycling conditions were maintained as follows: 94°C for 30 s, 40 cycles at 94°C for 10 s, 58°C for 20 s, and 61 cycles at 65°C for 10 s to create a melting curve. The experiments were performed with three independent biological replicates. Under normal growing condition, the DcACTIN gene was selected as the internal control to analyze gene expression and data of DcDWF4 in carrot petioles at 90 DAS were chosen as a calibrator for gene expression analysis (Tian et al., 2015). By contrast, in the analysis of gene expression after application of 24-EBL, the DcTUB gene was selected as the internal control. The expression of DcTUB gene was more stable under abnormal growth conditions.

Oligonucleotide sequences of genes involved in the biosynthesis, catabolism, and signaling pathway.