Plant materials and drought treatments

Prunus davidiana seeds (Pd) were collected from the Jinniu Mountain Scientific Research base of Shandong Institute of Pomology, Shandong, China, located at 35°38′N and 116°20′E. The seeds were grown in plastic pots (upper diameter 7.0cm, lower diameter 5.0cm, height 7.8cm) filled with mixed soil (vermiculite:humus = 1:1) (without chemical fertilizer application) and were well watered for 30d under greenhouse conditions with 24/18°C day/night, 16/8 h light/dark and 70% relative humidity [32]. In the experiment, there were two groups, a control group and a treated group. Each of them contained 10 peach seedlings. The drought stress treatments were carried out on ten Pd seedlings with similar stem lengths and leaf areas for ten days by withholding water until distinct wrinkling was observed in the top three leaves [29]. The control pot contained another ten similar Pd seedlings that were slightly watered every three days to keep the soil moist. Leaf samples from the treated and control groups were collected, immediately frozen in liquid nitrogen and stored at -70°C [1]. In the tissue expression pattern experiment, samples of five tissues including roots, stems, leaves, flowers and fruits were collected from the cultivar Sunagowase, immediately frozen in liquid nitrogen and stored at -70°C [1].