*2.9. Yeast Two-Hybrid (Y2H) Screen and Assays, and Bimolecular Fluorescence Complementation (BiFC) Assay*

In order to find out BAG9-interacting proteins in tomato, the coding sequences of *BAG9* were cloned into the pGBKT7 vector using gene-specific promoters (Table S3) and subsequently transferred into the AH109 yeast strain. The cDNA library building and Y2H screening were implemented as the manufacturer's protocol described (Takara, Shiga, Japan). SD-Trp-Leu-Ade-His plates were used for Y2H screening. Hsp20s in tomato were identified as BAG9-interacting proteins from Y2H screens. The coding sequences of Hsp20s were amplified by PCR using specific primers (Table S4) and cloned into a pGADT7 vector. Cotransformed bait-and-prey constructs were plated onto a selection medium lacking Trp, Leu, Ade, and His to analyze interactions. Before this study, pFGC-N-YFP and pFGC-C-YFP had been described for the BiFC vectors [46]. Gene-specific primers were used to amplify the full-length sequences of BAG9 and Hsp20s in PCRs and clone them into pFGC-N-YFP or pFGC-C-YFP vectors (Figure S5). To infiltrate *N. benthamiana*, plasmids were infectively introduced into *A. tumefaciens* GV3101 strains, according to previously described procedures [46]. During 48 h after infiltration, fluorescent signals from infected tissues were analyzed by a Zeiss LSM 780 confocal microscope (Zeiss LSM 780, Oberkochen, Germany) using appropriate filter sets (excitation wavelengths 488 nm and emission between 500 nm and 530 nm).
