*3.5. Expression Pattern of SlABG Genes under Abiotic Stress*

The promoter analysis of *SlBAG* genes indicated that these genes might be related to the response of tomato to different stresses. Here, the *SlBAG* gene expression of tomato leaves after osmotic stress (drought and salt), temperature stress (high temperature and cold) and signal molecular (ABA and H2O2) was analyzed by qRT-PCR (Figure 5). Under all these stress conditions, almost all *SlBAG* genes showed different expression patterns. Under drought treatment, the expression of *SlBAG5* and *SlBAG6* generally increased with prolonged treatment time, while *SlBAG9* expression decreased with time under drought stress. Under salt stress, the expression of *SlBAG1*, *SlBAG2*, *SlBAG5*, and *SlBAG6* was upregulated. In response to high temperature, the expression level of *SlBAG1*, *SlBAG2*, *SlBAG3*, *SlBAG7*, *SlBAG8*, and *SlBAG9* in general were upregulated, while *SlBAG6* was downregulated. For cold stress, the expression levels of *SlBAG1* and *SlBAG2* in general were increased, while *SlBAG4*, *SlBAG6* and *SlBAG8* was decreased. As far as ABA is concerned, the expression of *SlBAG1*, *SlBAG5*, and *SlBAG6* generally showed an upward trend, while the expression of *SlBAG2*, *SlBAG8*, and *SlBAG10* showed a downward trend. For H2O2, the expression of *SlBAG1*, *SlBAG4*, and *SlBAG5* in general increased while expression of *SlBAG7*, *SlBAG9*, and *SlBAG10* decreased. The cluster heat map of all treatment showed that the expression of *SlBAG5* and *SlBAG6* induced by osmotic stress and signal molecules clustered in the same group and most of the *SlBAG* genes could be regulated by high temperature.

**Figure 5.** Expression profiles of *SlBAG* genes in tomato seedlings under different abiotic stresses. 20-day-old tomato plants were treated with PEG6000 (P, 20%), NaCl (N, 100 mM), high-temperature (T, 42 ◦C), cold (C, 4 ◦C), cadmium (D, 50 uM), ABA (A, 100 uM), or H2O2 (H, 10 mM) for 0, 3, 6, 12, 24, and 48 h. Total RNA from tomato leaves at indicated time was extracted from different organs (root, stem, leaf, flower, green fruit, and red fruit) for qRT-PCR. Three independent biological repeats were performed (*n* = 3). The bar in the upper right corner represents the expression value of log2, and the change of expression level is represented by the change in color. Red indicates relatively high expression and blue indicates relatively low expression.
