Plant materials cultivation and physiological analysis of stress treatments

All of the Arabidopsis seeds and transgenic plants used in this study were in a Col-0 (Columbia) background. All plants were grown in a controlled growth chamber at 21–22°C under cool-white fluorescent light (80–100 μmol m⁻² s⁻¹) in a long day photoperiod (16 h light/8 h dark).

Arabidopsis seeds were germinated on half-strength Murashige and Skoog (1/2 MS) medium supplemented with 0.6% (w/v) sucrose and 0.7% (w/v) agar. After 7 days, seedlings were transferred to 1/2 MS medium with 100–400 mM mannitol or 50–150 mM NaCl and treated for another 7 days. Mannitol and NaCl were added to different 1/2 MS medium. Seven-day seedlings(normal 1/2 MS medium) were transferred to above-mentioned 1/2 MS medium.

Arabidopsis were also grown in garden soil (Basic substrate No. 1, Pindstrup Mosebrug A/S, Denmark) without additional fertilizer, and were maintained in a greenhouse under standard growing conditions (Weigel and Glazebrook, 2002). Before salinity and drought treatment, young plants were watered once per week. Three-week plants were used for salinity or drought treatment, by watering with 200 mM NaCl solution or depriving of water respectively for 4 weeks. After drought treatment, they are rewaterd for a week.