Study : Arabidopsis thaliana strain:Columbia Transcriptome or Gene expression
Identification
Name
Arabidopsis thaliana strain:Columbia Transcriptome or Gene expression
Identifier
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Source
Description
MicroRNAs (miRNAs) are a class of endogenous regulatory RNAs that play an important role in many biological processes. In plants, HYPONASTIC LEAVES1 (HYL1) is a double-stranded RNA binding protein that facilitates DICER-LIKE1 (DCL1) to process primary miRNA (pri-miRNA) into mature miRNA. Recent studies showed that HYL1 is a short lived phospho-protein and is stabilized indirectly in the light by an E3 ligase, COP1, but whether the phosphorylation status is related to HYL1 stability and the mechanism by which HYL1 is constitutively stabilized remain unknown. Here, we show that SMEK1, as a suppressor of MEK, stabilizes HYL1 by inhibiting MPK3-dependent phosphorylation of HYL1 in plants. Loss-of-function of SMEK1 exhibit pleiotropic developmental abnormalities, resembling mutants that affect miRNA activities. In smek1 HYL1 was significantly reduced, which was concomitant with globally decreased levels of mature miRNAs. HYL1 is reduced in smek1 mutants either in the light or in the dark, indicating that SMEK1-mediated HYL1 stabilization is independent of the COP1 pathway. Treatments by kinase inhibitor or phosphatase inhibitor increases or reduces HYL1, respectively, suggesting that phosphorylation is anti-correlated with HYL1 stability. In vitro kinase assay showed that SMEK1 inhibits the activation of MPK3, a kinase of HYL1, indicating that SMEK1 acts as a suppressor of the MAPK pathway. Taken together, our work thus uncovers how the stability of HYL1 is regulated by the phosphorylation events, and identifies that SMEK1 acts as a negative regulator of the MAPK pathway to promote miRNA biogenesis.
Data files
Genotype
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