SERRATE is a novel nuclear regulator in primary microRNA processing in Arabidopsis

Abstract

SummaryThe Arabidopsis gene SERRATE (SE) controls leaf development, meristem activity, inflorescence architecture and developmental phase transition. It has been suggested that SE, which encodes a C 2 H 2 zinc finger protein, may change gene expression via chromatin modification. Recently, SE has also been shown to regulate specific microRNAs (miRNAs), miR165/166, and thus control shoot meristem function and leaf polarity. However, it remains unclear whether and how SE modulates specific miRNA processing. Here we show that the se mutant exhibits some similar developmental abnormalities as the hyponastic leaves1 (hyl1) mutant. Since HYL1 is a nuclear double-stranded RNA-binding protein acting in the DICER-LIKE1 (DCL1) complex to regulate the first step of primary miRNA transcript (pri-miRNA) processing, we hypothesized that SE could play a previously unrecognized and general role in miRNA processing. Genetic analysis supports that SE and HYL1 act in the same pathway to regulate plant development. Consistently, SE is critical for the accumulation of multiple miRNAs and the trans-acting small interfering RNA (ta-siRNA), but is not required for sense posttranscriptional gene silencing. We further demonstrate that SE is localized in the nucleus and interacts physically with HYL1. Finally, we provide evidence that SE and HYL1 probably act with DCL1 in processing primiRNAs before HEN1 in miRNA biogenesis. In plants and animals, miRNAs are known to be processed in a stepwise manner from pri-miRNA. Our data strongly suggest that SE plays an important and general role in primiRNA processing, and it would be interesting to determine whether animal SE homologues may play similar roles in vivo.

Genome-Wide Analysis Uncovers Regulation of Long Intergenic Noncoding RNAs in Arabidopsis

“…This protein cooperates with HYL1 and DCL1 to process pri-miRNA (Yang et al, 2006), and along with ABH1/CBP80 and CBP20, it is required for mRNA and pri-miRNA splicing (Laubinger et al, 2008). The SEmediated splicing event is believed to prevent generation of related siRNAs to trigger posttranscriptional gene silencing .…”

The role of decapping proteins in the miRNA accumulation inArabidopsis thaliana

“…SE is one of the miRNA processing factors, and the accumulation of pri-miRNAs increases in the se mutant, se-1. 40 We first examined the levels of class I pri-miRNAs; primiR164a and pri-miR164c (referred to as pri-miR164s) and primiR167a, pri-miR167b, pri-miR167c and pri-miR167d (referred to as pri-miR167s), in the decapping mutants. The levels of primiR164s and pri-miR167s did not increase in dcp1-1, dcp2-1 or vcs-6, unlike in se-1 ( Fig.…”

Fine tuning of auxin signaling by miRNAs

“…The processing of pri-miRNAs to pre-miRNAs in plants is mediated by the Dicer-like protein 1 (DCL1) instead of DROSHA (Park et al, 2002;Reinhart et al, 2002;Papp et al, 2003;Kurihara and Watanabe, 2004). This step also involves cooperation of other proteins like HYPONASTIC LEAVES1 (HYL1) , Vazquez et al, 2004, HUA ENHANCER1 (HEN1) (Boutet et al, 2003;Park et al, 2005) and SERRATE (SE) (Yang et al, 2006a). The further cleavage of pre-miRNA to a miRNA:miRNA* duplex is mediated by DCL1 in nucleus (Papp et al, 2003;Kurihara and Watanabe, 2004) and the duplex is transported to cytoplasm by HASTY (HST), the plant ortholog of EXP5 where it gets incorporated into RISC complex.…”