BIL-c
Three rice lines with contrasting levels of drought tolerance: IR77298-14-1-2-10 (drought-tolerant; BIL), IR87705-7-15-B (drought-tolerant; NIL) and IR64 (drought susceptible) were used. They were planted in potted soil in greenhouse subjected to natural solar radiation. All plants were grown under well-water conditions up to booting stage. For each rice line, two experimental conditions were set up, which were drought and control. Drought stress was imposed on the rice plants at booting stage by discontinuing watering. The treatment lasted for approximately 7 days until the observation of leaf rolling of the stressed plants during their heading stage. At that point, mature inflorescences of control and drought-treated pots were collected, snap frozen and kept in -80˚C until use. The inflorescence tissues include rachis, branches and spikelets from 3 plants per experimental group. Taking account of the two experimental factors: rice line and experimental condition, a total of six small RNA libraries were constructed. Total RNA of the inflorescence tissues was isolated using mirVana miRNA Isolation Kit (Invitrogen) according to manufacturer’s protocol. Small RNA libraries were constructed and sequenced at Beijing Genomics Institute (BGI).