data4
Plant material and sample preparation T. aestivum L. variety Zhoumai 18 was used in this experiment. Plants were grown in an experimental field of Henan Agricultural University, Zhengzhou, China. Plants that derived from a single individual were grown in the same experimental field in a line during the winter, and in December, they were transplanted into a greenhouse. Anthesis was recorded when 50% of the plants reached the flowering stage. Immature seeds were collected 14 d after anthesis from the main spikes. Well-developed mature seeds from the main spikes were collected in April and soaked in running tap water for 4 h. Immature and mature seeds were surface-sterilized in 75% (v/v) ethanol, followed by mercuric chloride solution, and then rinsed with sterilized distilled water. Immature embryo (IMEs) and mature embryos (MEs) were extracted from sterilized seeds on a clean bench, placed  in sterile petri dishes containing solid Murashige and Skoog (MS) medium. They were then grown in a culture room at 22–24 °C in the dark. MEs and IMEs were harvested in three biological replicates at 3days culture (DC), 6 DC, and 15 DC, snap-frozen in liquid nitrogen, and stored at -80 °C until RNA extraction.   sRNA library construction and RNA sequencing Total RNA was extracted from IME and ME callus in three biological replicates. RNA samples in three biological replicates were mixed and used as single RNA pools for the construction of libraries. PCR products were sequenced using a HiSeq 2000 Sequencing System (Illumina, San Diego, CA, USA) according to the manufacturer’s instructions. 