## 2 Results
### TrHSFB2a Negatively Regulates Salt Tolerance in Arabidopsis  
To check how the _TrHSFB2a_ gene functions under salt stress conditions, we observed the overexpression and RNA interference T-DNA lines of _Arabidopsis_ in \({}^{1}\)/2 MS media and in soil. At five days old, seedlings were shifted to 1/2 MS+Agar plates, supplemented with 100 mM or 150 mM NaCl, and phenotypic data were recorded at 10 d of transplanting. The results showed that _TrHSFB2a_ had a significantly lower rate of survival (around 20%) compared to wild type (47.33%), and RNA interference T-DNA lines showed a significantly higher survival rate (more than 65%) than that of wild type (Figure 8), suggesting that overexpression of _TrHSFB2a_ significantly reduced tolerance of salt, while RNA interference of _TrHSFB2a_ can enhance salt tolerance of transformed _Arabidopsis_ at the seedling stage. Root length was significantly higher in T-DNA lines compared to wild type under 100 mM and  
Figure 7: Comparison of heat stress tolerance of overexpressing _TrHSFB2a_ lines and RNA interference T-DNA lines with wild type grown in nutrient soil (peat moss, vermiculite and perlite, 3:1:1) for 25 days and transferred to an incubator adjusted with 35 \({}^{\circ}\)C temperature. (**a**) Display _Arabidopsis_ phenotypes after high-temperature treatment and recovery of plants after transferring to normal growth conditions. (**b–f**) display graphical representations of plants drying rate (%), dry weight (g), photochemical efficiency (Fv/Fm), relative electrical conductivity (%) and MDA contents (nmole/g FW), respectively. Bars represent mean \(\pm\) SD values, and different small letters (a, b and c) represent significant statistical difference among means (one-way ANOVA, followed by Tukey test) between different lines. 150 mM salt stress, while one overexpression line (OE-3) showed significantly reduced roots length than that of wild type, and one (OE-3) did not show a significant difference with the wild type under both salt stress treatments. However, the total fresh weight was significantly higher in T-DNA lines and significantly lower in overexpression lines compared to wild type, respectively (Figure 8). Simultaneously, 10 d old wild and transgenic _Arabidopsis_ lines grown on 1/2 MS+Agar media were transferred into the soil, grown additionally for three weeks in nutrient soil, then irrigated with 100 mM, 200 mM and 300 mM NaCl gradients water, each twice after every two days (Figure 9a,b). RWC, EC, photochemical efficiency and performance index were measured after two times of 100 mM and 2 times 200 mM saline water irrigation, on the 8 th d of treatment. Results showed that RWC, photochemical efficiency and performance index on an absorption basis were significantly lower in overexpression lines and were significantly higher in T-DNA lines compared to wild type, respectively. In contrast, EC % had significantly increased in overexpression lines and was significantly lower in T-DNA lines compared to wild type (Figure 9c-f). The data of physiological analysis, together with phenotypic observations, indicated that overexpression of _TrHSFB2a_ reduced salt tolerance, while RNA interference for this gene can improve the salt tolerance of Arabidopsis at seedling and developing growth stages. Figure 8: Comparison of salt stress tolerance of overexpressing _TrHSFB2a_ lines and RNA interference T-DNA lines with wild type on 1/2 MS medium supplemented with 100 or 150 mM NaCl. **(a,b)** show wild (WT), T-DNA lines (T-77 and T-95) and overexpression lines (OE3 and OE4) TrHSFB2a lines grown on 1/2 MS medium supplemented with 100 mM and 150 mM NaCl, respectively, **(c–e)** show roots growth on 1/2 MS medium supplemented with 100 mM and 150 mM NaCl, respectively; **(f)** plants survival/yellowing-related phenotypes on 1/2 MS medium supplemented with 150 mM NaCl. **(g–i)** Show root length (cm), fresh weight (g) and survival rate (%) measured after 10 days of transplanting.