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. Author manuscript; available in PMC: 2018 Jul 11.
Published in final edited form as: New Phytol. 2017 Oct 19;216(4):1002–1017. doi: 10.1111/nph.14834

Fig. 3.

Fig. 3

Mechanisms of plant microRNA (miRNA) turnover. miRNA degradation starts with the removal of the methyl group at the 3′ end by SMALL RNA DEGRADING NUCLEASE 1 (SDN1), which is followed by 3′ uridylation through HEN1 SUPPRESSOR 1 (HESO1) and/or UTP:RNA URIDYLYLTRANSFERASE 1 (URT1). The tailed miRNAs are subsequently degraded by an unknown exonuclease. SDN1 and nucleotidyl transferases (HESO1 and URT1) can act on both ARGONAUTE (AGO)-bound miRNAs and free miRNAs in the cytoplasm. Free miRNAs are also degraded by SDN1 directly. The degradation of AGO1 via autophagy may also contribute to miRNA turnover.