%0 Journal Article %A Feng Wang %A Nathan R. Johnson %A Ceyda Coruh %A Michael J. Axtell %T Genome-Wide Analysis of Single Non-Templated Nucleotides in Plant Endogenous siRNAs and miRNAs %D 2016 %R 10.1101/044982 %J bioRxiv %P 044982 %X Plant small RNAs are subject to various modifications. Previous reports revealed widespread 3' modifications (truncations and non-templated tailing) of plant miRNAs when the 2'-C-methyltransferase HEN1 is absent. However, non-templated nucleotides in plant heterochromatic siRNAs have not been deeply studied, especially in wild-type plants. We systematically studied non-templated nucleotide patterns in plant small RNAs by analyzing small RNA sequencing libraries from Arabidopsis. tomato, Medicago, rice, maize, and Physcomitrella. Elevated rates of non-templated nucleotides were observed at the 3' ends of both miRNAs and endogenous siRNAs from wild-type specimens of all species. 'Off-sized' small RNAs, such as 25 and 23 nt siRNAs arising from loci dominated by 24 nt siRNAs, often had very high rates of 3'-non-templated nucleotides. The same pattern was observed in all species that we studied. Further analysis of 24 nt siRNA clusters in Arabidopsis revealed distinct patterns of 3'-non-templated nucleotides of 23 nt siRNAs arising from heterochromatic siRNA loci. This pattern of non-templated 3' nucleotides on 23 nt siRNAs is not affected by loss of known small RNA 3'-end modifying enzymes, and may result from modifications added to longer heterochromatic siRNA precursors. %U https://www.biorxiv.org/content/biorxiv/early/2016/05/12/044982.full.pdf