期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2018
卷号：115
期号：31
页码：8037-8042
DOI：10.1073/pnas.1807403115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Phased, secondary siRNAs (phasiRNAs) represent a class of small RNAs in plants generated via distinct biogenesis pathways, predominantly dependent on the activity of 22-nt miRNAs. Most 22-nt miRNAs are processed by DCL1 from miRNA precursors containing an asymmetric bulge, yielding a 22/21-nt miRNA/miRNA* duplex. Here we show that miR1510, a soybean miRNA capable of triggering phasiRNA production from numerous nucleotide-binding leucine-rich repeat ( NB-LRR s), previously described as 21 nt in its mature form, primarily accumulates as a 22-nt isoform via monouridylation. We demonstrate that, in Arabidopsis , this uridylation is performed by HESO1. Biochemical experiments showed that the 3′ terminus of miR1510 is only partially 2′- O -methylated because of the terminal mispairing in the miR1510/miR1510* duplex that inhibits HEN1 activity in soybean. miR1510 emerged in the Phaseoleae ∼41–42 million years ago with a conserved precursor structure yielding a 22-nt monouridylated form, yet a variant in mung bean is processed directly in a 22-nt mature form. This analysis of miR1510 yields two observations: ( i ) plants can utilize postprocessing modification to generate abundant 22-nt miRNA isoforms to more efficiently regulate target mRNA abundances; and ( ii ) comparative analysis demonstrates an example of selective optimization of precursor processing of a young plant miRNA.
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