(A) A brief scheme of microsome and MBP isolation. (B) Size (in nucleotides) distribution of sRNAs in total extract (T), microsome (M), and an ER pull-down (ER-IP). RPMR, reads per million 45S rRNA (see Materials and methods). Error bar indicates standard deviation from three biological replicates. (C) Composition of sRNAs in three size classes in various samples. TP, total polysome; MBP, membrane-bound polysome. Each column represents a biological replicate. (D) Size (in nucleotides) distribution of sRNAs in T, TP, and MBP. (E) Abundance of annotated miRNAs and miRNA*s in MBP and TP. (F) Abundance of siRNAs from TAS1, 2, 3, and four loci in TP and MBP. All siRNAs mapping to the TAS loci were sampled in the four size classes. (G–H) A set of endogenous siRNAs was enriched in the MBP fraction. The genome was tiled into 100 bp windows and the abundance of 21-nt (G) or 22-nt (H) sRNAs in these windows were compared between MBP and TP samples. Regions showing enrichment (DEG region) are in green.