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RNA Interference in Ticks
Published on: January 20, 2011
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A fungal Argonaute interferes with RNA interference
Quyet Nguyen1, Akihide Iritani1, Shuhei Ohkita1
1Laboratory of Cell Function and Structure, Graduate School of Agricultural Science, Kobe University, Nada Kobe 657-8501, Japan.
Nucleic Acids Research
|January 9, 2018
Summary
In Pyricularia oryzae, the Argonautes protein MoAGO2 surprisingly impedes RNA interference (RNAi). Gene knockout studies reveal MoAGO2 hinders silencing of parasitic elements like MAGGY retrotransposons and mycoviruses.
Area of Science:
- Molecular Biology
- Genetics
- Fungal Biology
Background:
- Small RNA (sRNA)-mediated gene silencing, including RNA interference (RNAi), relies on Argonaute (AGO) proteins.
- AGO proteins form complexes with sRNAs to direct gene silencing.
- Pyricularia oryzae (Magnaporthe oryzae) possesses three AGO genes, with their specific roles in RNAi not fully elucidated.
Purpose of the Study:
- To investigate the function of MoAGO2, one of the three AGO genes in Pyricularia oryzae, in RNA-mediated gene silencing.
- To determine the role of MoAGO2 in RNA interference against endogenous parasitic elements like retrotransposons and mycoviruses.
- To elucidate the mechanism by which MoAGO2 influences RNAi efficacy.
Main Methods:
- Gene knockout (KO) studies were performed to generate MoAGO1, MoAGO2, and MoAGO3 mutants.
- RNA interference (RNAi) assays were conducted using hairpin RNA and retrotransposon (MAGGY) triggers.
- Deep sequencing was employed to analyze small interfering RNA (siRNA) populations associated with AGO proteins.
- Site-directed mutagenesis was used to assess the importance of sRNA binding and slicer activity of MoAGO2.
Main Results:
- MoAGO1 and MoAGO3 play additive or redundant roles in hairpin RNA- and MAGGY-triggered RNAi.
- Surprisingly, MoAGO2 knockout mutants (Δmoago2) exhibited enhanced gene silencing.
- Transcript levels of MAGGY and mycoviruses were significantly reduced in Δmoago2 mutants, indicating MoAGO2 impedes RNAi against these elements.
- Deep sequencing revealed that repeat- and mycovirus-derived siRNAs are primarily associated with MoAGO2 and MoAGO3.
- sRNA binding, but not slicer activity, of MoAGO2 was crucial for its ability to diminish RNAi efficacy.
Conclusions:
- MoAGO2 acts as an inhibitor of RNA interference in Pyricularia oryzae, contrary to the typical silencing role of AGO proteins.
- MoAGO2 impedes the silencing of parasitic elements, suggesting a role in regulating the interaction between the host and its genetic parasites.
- Distinct sRNA-mediated gene regulation pathways may interact through competition for sRNA binding, mediated by proteins like MoAGO2.
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