*2.3. Construction of Plant Expression Vector and Tomato Transformation*

To generate the *BAG9*-overexpressing lines, *BAG9* full-length coding sequence (CDS) was amplified with the forward primer (5 -gggcgcgccgatatcgtcgacATGGAGAATCTCTTCAATTGG TCC-3 ) and reverse primer (5 -aacatcgtatgggtaggtaccGCTGCCGGAAACAATGGAG-3 ) using tomato complementary DNA (cDNA) as the template. To insert the PCR product into the pFGC1008-HA vector behind the cauliflower mosaic virus (CaMV) 35S promoter, the product was digested with *Asc*I and *Kpn*I. As described previously, CRISPR/Cas9 vectors were constructed and used to generate *bag9* mutants [38]. Using the CRISPR-P web tool (http://crispr.hzau.edu.cn/ (accessed on 11 September 2020)), the target sequences (5 -GCTCGCCGTCGCTATTCCTC-3 ) were achieved and subsequently introduced into the *Bbs*I site of the AtU6-sgRNA-AtUBQ-Cas9 vectors following annealing into the double strands. The fragments of the AtU6-sgRNA-AtUBQ-Cas9 were fused to the *Kpn*I and *Hind*III sites of the pCAMBIA1301 binary vectors. The final vectors were introduced into tomato AC via *A. tumefaciens*-mediated transformation. A homozygous T2 *BAG*9 overexpressing line was used for experiments and identified by Western blot using an anti-HA (26183, Thermo Fisher Scientific, Waltham, MA, USA) monoclonal antibody (Figure S1A). *bag9* mutant contained mutations near the protospacer adjacent motif (PAM), which induced mismatched amino-acid sequence and terminated translation (Figure S1B).

#### *2.4. Total RNA Extraction and Gene-Expression Analysis*

RNA extraction kits were used for obtaining total RNA (DP419, Tiangen, Beijing, China). The HiScript Q RT SuperMix for the quantitative real-time PCR (+gDNA wiper) Kit (R223, Vazyme, Nanjing, China) was used to produce first-strand cDNA from 500 ng

of total RNA. ChamQ Universal SYBR qPCR Master Mix (Q711, Vazyme, Nanjing, China) and Light Cycler® 480 II Real-Time PCR detection system (Roche, Basel, Switzerland) were used in the RT-qPCR. In this program, predenaturation at 95 ◦C for 3 min, followed by 40 cycles of denaturation at 95 ◦C for 30 s, annealing at 58 ◦C for 15 s and 72 ◦C for 30 s, and a final extension at 72 ◦C for 30 s. Table S2 listed primers used for RT-qPCR, as well as tomato *Actin* as an internal control. To calculate relative gene expression, the 2−ΔΔCT method was used, and a heat-map analysis was conducted using MEV version 4.9 (http://www.mev.tm4.org/ (accessed on 10 June 2020)). At the bottom, the intensity of the color bar showed the intensity of expression.
