*4.5. Plant Growth Conditions and Treatments*

Nipponbare rice seeds (*O. sativa* L. *ssp. japonica*) were surface-sterilized with 10% sodium hypochlorite solution for 30 min then sown on 1/2 MS (Murashige & Skoog) solid medium and cultured in a light incubator. After 2 weeks, the seedlings were at the two true leaf stage. They were transplanted into Hoagland's nutrient solution and cultured in an artificial climate chamber under controlled conditions (14 h light at 28 ◦C/10 h dark at 22 ◦C; relative humidity 70%). The rice seedlings were subjected to various stresses at the three-leaf stage (4 weeks) [50].

For the drought, salt, and hydrogen peroxide stress treatments, the rice seedlings were transferred to Hoagland's nutrient solution containing 20% polyethylene glycol (PEG)-6000 (*w*/*v*), 150 mM NaCl, or 2% hydrogen peroxide (*v*/*v*), respectively. For the ABA treatment, the rice seedlings were cultured on 1/2 MS solid medium containing 10 µM ABA. The control group was maintained on normal nutrient solution or medium. All other culture conditions were the same as described above. Treated rice tissues were harvested at 0 h, 1 h, 2 h, 4 h, 6 h, 12 h, 24 h, and 48 h. The samples were immediately placed in liquid nitrogen and stored at −80 ◦C until use. Untreated material was used as a control. The experimental procedure was repeated at least three times.
