The SnRK2 kinases modulate miRNA accumulation in Arabidopsis.

Jun Yan,Chuan-Chih Hsu,Hairong Zhang,W Andy Tao,Yang Zhao,Pengcheng Wang,Xiaohong Zhu,Jian-Kang Zhu,Bangshing Wang,Qiming Wang,Kai Tang,Chunzhao Zhao,Jianming Li,Yueh-Ju Hou,Claudia Köhler

doi:10.1371/journal.pgen.1006753

Abstract

MicroRNAs (miRNAs) regulate gene expression and play critical roles in growth and development as well as stress responses in eukaryotes. miRNA biogenesis in plants requires a processing complex that consists of the core components DICER-LIKE 1 (DCL1), SERRATE (SE) and HYPONASTIC LEAVES (HYL1). Here we show that inactivation of functionally redundant members of the SnRK2 kinases, which are the core components of abscisic acid (ABA) and osmotic stress signaling pathways, leads to reduction in miRNA accumulation under stress conditions. Further analysis revealed that the steady state level of HYL1 protein in plants under osmotic stress is dependent on the SnRK2 kinases. Additionally, our results suggest that the SnRK2 kinases physically associate with the miRNA processing components SE and HYL1 and can phosphorylate these proteins in vitro. These findings reveal an important role for the SnRK2 kinases in the regulation of miRNA accumulation and establish a mechanism by which ABA and osmotic stress signaling is linked to miRNA biogenesis.

Highlights

MicroRNAs are non-coding RNAs that impact various biological processes by regulating mRNA cleavage or translation in a sequence-specific manner
Our study provides a new mechanism of regulation of miRNA biogenesis and paves the way for further understanding of the impact of abscisic acid (ABA) and osmotic stress signaling on miRNA production
During the characterization of the snrk2.2/3/6 triple mutant, we noticed that compared with its wild type control, both the rosette and cauline leaves are smaller, and older rosette leaves and cauline leaves are serrated in the snrk2.2/3/6 mutant under our plant growth room conditions (Fig 1A and 1B and S1 Fig)

Summary

Introduction

MicroRNAs (miRNAs) are non-coding RNAs that impact various biological processes by regulating mRNA cleavage or translation in a sequence-specific manner. The core components of miRNA processing complex include the RNAse III enzyme DICER-LIKE 1 (DCL1), the zinc finger protein SERRATE (SE) and the double-stranded RNA binding protein HYPONASTIC LEAVES (HYL1) [1,2,3,4,5,6,7,8,9,10]. STABLIZED 1 (STA1) and XAP5 CIRCADIAN TIMEKEEPER (XCT) can modulate miRNA accumulation through regulation of DCL1 transcript level [22, 23]. Several other proteins, such as SICKLE (SIC), Modifier of SNC1, 2 (MOS2), AtGRP7 and THO2 are additional players involved in miRNA accumulation [24,25,26,27]. A recent study suggested that HYL1 is a putative substrate of the mitogen-activated protein kinase MPK3 in both Arabidopsis and rice [29]

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Discussion

Conclusion