*2.2. RNA Extraction, cDNA Synthesis, and qRT-PCR*

Total RNA was extracted using the RNAprep pure Plant Kit (TianGen, Beijing, China). cDNA was synthesized using the PrimeScript™ RT Master Mix kit (Perfect Real Time) (Takara, Dalian, China). Based on the full-length coding sequences (CDSs) of *PlNCEDs* in transcriptome data, qRT-PCR primers were designed with the Primer Premier 5.0 software. *PlACTIN* (GenBank accession number JN105299.1) was used as the reference gene [32]. The primers used for qRT-PCR are listed in Supplementary Table S1. qRT-PCR was performed using TB Green® Premix Ex Taq™ II (Tli RNaseH Plus) (Takara, Dalian, China). The reactions were accomplished according to the two-step method—holding stage: 95 ◦C for 30 s; cycling stage: 40 cycles of 95 ◦C for 5 s, 60 ◦C for 30 s; and melt curve stage: 95 ◦C for 15 s, 60 ◦C for 1 min, 95 ◦C for 15 s. Each experiment was performed with three biological and three technical replicates. The relative expression levels of genes were calculated according to the 2−ΔΔCt method, and the error bars represent the standard error from three independent experiments. The results were analyzed by GraphPad Prism 8.0 for ANOVA.
