On December 29, 2017, Prof. Yijun Qi’s group from School of Life Sciences at Tsinghua University published a research article in Molecular Cell, reporting a new role for Arabidopsis Argonuate1 in promoting gene transcription in response to hormones and stresses.

The Argonaute (AGO) family proteins are known as core effectors of RNA interference (RNAi) pathways in eukaryotes. AGO proteins associate with different classes of small RNAs (sRNAs) that are processed from double-stranded or stem-loop structured precursor RNAs by Dicer or Dicer-like (DCL) proteins. Guided by sRNAs, AGO proteins bind target sequences through base-pairing, which causes the cleavage of target RNAs and/or the recruitment of cofactors to mediate post-transcriptional or transcriptional gene silencing (PTGS or TGS).

Arabidopsis AGO1 is the founding member of the AGO family. AGO1 predominantly binds microRNAs (miRNAs) and post-transcriptionally represses target genes via mRNA cleavage and/or translational repression in the cytoplasm. However, it has been previously shown that AGO1 is also localized in the nucleus, suggesting a nuclear role for AGO1.

In this study, Qi and colleagues investigated the role of nuclear AGO1 in gene regulation on a genome-wide scale. They found that AGO1 binds to the chromatin of genic regions and positively regulates target gene transcription. They demonstrated that AGO1 binding to chromatin requires sRNAs and the SWI/SNF chromatin remodeling complexes. Unexpectedly, and perhaps more importantly, they found that AGO1 binding to its target genes is responsive to plant hormones, biotic and abiotic stresses. These findings reveal an unsuspected role for AGO1 in promoting gene transcription in response to plant hormones and stresses.