*4.13. Real-Time PCR*

Total RNA was extracted from the leaves using the Total RNA Kit (BioTeke Corporation, Beijing, China), following the manufacturer's instructions. Integrity of the RNA was verified by agarose gel electrophoresis. Synthesis of the cDNA was performed from the total RNA samples using the PrimeScript™ RT Reagent Kit, according to the protocol with gDNA Eraser (TaKaRa, Dalian, China). All of the primer sequences are shown in Table 2. *EF1α* gene was used as the internal control under abiotic stress [55], and the *SlCAC* gene was selected as an internal standard during tomato development [56] to quantitate the expression of *SlUGlcAE* genes. Real-time PCR was performed using CFX96 Touch™ real-time PCR system (Bio-Rad, Hercules, CA, USA) with a SYBR Premix Ex Taq™ II Kit (Bio-Rad). The reactions were carried out in the following conditions: denaturation at 94 ◦C for 4 min, 40 cycles of 5 s at 95 ◦C, 30 s at 60 ◦C, 15 s at 95 ◦C, 20 s at 60 ◦C, and 15 s at 95 ◦C. Three biological duplications were used. The 2−∆∆*C*<sup>t</sup> method was used to visualize and analyze the real-time PCR data [57,58].


**Table 2.** Primer sequences used for quantitative real-time PCR in the paper.
