Extended Data Figure 9: miRNA-directed easiRNA biogenesis from activated transposons. | Nature

Extended Data Figure 9: miRNA-directed easiRNA biogenesis from activated transposons.

From: miRNAs trigger widespread epigenetically activated siRNAs from transposons in Arabidopsis

Extended Data Figure 9

When TEs are epigenetically activated, through the loss of DNA methylation and/or heterochromatin, transposon mRNA transcripts become preferentially targeted by miRNAs (DCL1 dependent) bound by AGO1. Productive cleavage of transposon transcripts engages RDR6 and DCL4, which generate 21-nucleotide easiRNAs from transposon ORFs—in a PTGS mechanism—that are then loaded into AGO1 and, thus, prevents engagement of RDR2 and RdDM. This antagonism accounts for the retention of miRNA binding sites by transposons to evade long-term heritable silencing, elicited by DNA methylation via RDR2. This model also accounts for the retention of the miRNA-directed mechanism by the host organism, in order to generate easiRNAs to silence TEs when they are epigenetically reprogrammed in the germ line.

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