Embryo_Endosperm
Oat (cv. Matilda, Lantm nnen, Sval v, Sweden) was grown in controlled growth chambers (Biotron, SLU-Alnarp, Sweden) under fluorescent light (200  mol m-2 s-1) during a 16/8 hour and 21 C /18 C light/dark cycle at 60% humidity. For transcriptome analyses grains were harvested at a mid-developmental stage and embryos were manually dissected using a scalpel and snap freezed into liquid nitrogen. Liquid endosperm was squeezed out from the grain and collected using a spatula which was then dipped into liquid nitrogen.  For transcriptome analyses, total RNA was extracted from frozen tissues by homogenizing material in Plant RNA Reagent according to instructions (Invitrogen, Carlsbad, USA). For PCR validation experiments, seed tissues were first ground in steel containers using metal beads in a mixer mill (MM400, Retsch, Haan, Germany), before extraction of RNA as described above. RNA integrity and concentration was determined using Experion RNA StdSens analysis kit (BioRad, Hercules, USA). Total RNA was DNase treated (TurboDNase, Ambion, Carlsbad, USA) before sequencing. Libraries were prepared at BGI (Shenzhen, China) according to their library preparation protocol and oat embryo and endosperm RNA libraries were sequenced through Illumina sequencing platform HiSeq 2000 as unpaired-end reads. Public hexaploid oat seed transcriptome was downloaded from NCBI SRA.