ARGONAUTE10 promotes the degradation of miR165/6 through the SDN1 and SDN2 exonucleases in Arabidopsis
Date
2017-02-23
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Public Library of Science (PLoS)
Abstract
The degradation of small RNAs in plants and animals is associated with small RNA 30 truncation
and 30 uridylation and thus relies on exonucleases and nucleotidyl transferases.
ARGONAUTE (AGO) proteins associate with small RNAs in vivo and are essential for not
only the activities but also the stability of small RNAs. AGO1 is the microRNA (miRNA)
effector in Arabidopsis, and its closest homolog, AGO10, maintains stem cell homeostasis
in meristems by sequestration of miR165/6, a conserved miRNA acting through AGO1.
Here, we show that SMALL RNA DEGRADING NUCLEASES (SDNs) initiate miRNA degradation
by acting on AGO1-bound miRNAs to cause their 30 truncation, and the truncated
species are uridylated and degraded. We report that AGO10 reduces miR165/6 accumulation
by enhancing its degradation by SDN1 and SDN2 in vivo. In vitro, AGO10-bound
miR165/6 is more susceptible to SDN1-mediated 30 truncation than AGO1-bound miR165/
6. Thus, AGO10 promotes the degradation of miR165/6, which is contrary to the stabilizing
effect of AGO1. Our work identifies a class of exonucleases responsible for miRNA 30 truncation
in vivo and uncovers a mechanism of specificity determination in miRNA turnover.
This work, together with previous studies on AGO10, suggests that spatially regulated
miRNA degradation underlies stem cell maintenance in plants.
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Yu Y, Ji L, Le BH, Zhai J, Chen J, Luscher E, et al. (2017) ARGONAUTE10 promotes the degradation of miR165/6 through the SDN1 and SDN2 exonucleases in Arabidopsis. PLoS Biol 15(2): e2001272. doi:10.1371/journal. pbio.2001272