A fungal Argonaute interferes with RNA interference

Abstract

Small RNA (sRNA)-mediated gene silencing phenomena, exemplified by RNA interference (RNAi), require a unique class of proteins called Argonautes (AGOs). An AGO protein typically forms a protein–sRNA complex that contributes to gene silencing using the loaded sRNA as a specificity determinant. Here, we show that MoAGO2, one of the three AGO genes in the fungus Pyricularia oryzae (Magnaporthe oryzae) interferes with RNAi. Gene knockout (KO) studies revealed that MoAGO1 and MoAGO3 additively or redundantly played roles in hairpin RNA- and retrotransposon (MAGGY)-triggered RNAi while, surprisingly, the KO mutants of MoAGO2 (Δmoago2) showed elevated levels of gene silencing. Consistently, transcript levels of MAGGY and mycoviruses were drastically reduced in Δmoago2, supporting the idea that MoAGO2 impeded RNAi against the parasitic elements. Deep sequencing analysis revealed that repeat- and mycovirus-derived small interfering RNAs were mainly associated with MoAGO2 and MoAGO3, and their populations were very similar based on their size distribution patterns and positional base preference. Site-directed mutagenesis studies indicated that sRNA binding but not slicer activity of MoAGO2 was essential for the ability to diminish the efficacy of RNAi. Overall, these results suggest a possible interplay between distinct sRNA-mediated gene regulation pathways through a competition for sRNA.

Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

“…We here propose to add a new genus named Penoulivirus since the representative member is Penicillium sumatrense ourmia-like virus 1 (PsOulV1). The new genus will also include the previously described Pyricularia oryzae ourmialike virus (Nguyen et al 2018) which shows 46.25% identity with PsOulV1.…”

Interspecies Communication in Holobionts by Non-Coding RNA Exchange

“…In eukaryotes, small ncRNAs are recognized by conserved RNA-binding proteins that belong to the argonaute family (Ago) [49]. Canonical and Ago-like proteins are encoded by the vast majority of eukaryotic genomes from fungi [50,51] to plants [52,53] and animals [54], ensuring a molecular background for the action of internal or external small ncRNAs [55,56]. In the cytoplasm of animal cells, a member of the argonaute protein family Ago2 is a key component of the RNA-induced silencing complex (RISC), which the base complementarity between the small RNA and its target will guide.…”

Nicotiana benthamiana Argonaute10 plays a pro‐viral role in Bamboo mosaic virus infection

“…Similar to AtAGO10, rice AGO18 (Oryza sativa (Os)AGO18) competes with OsAGO1 for association with miR168, thereby increasing OsAGO1 protein level that is essential for antiviral RNAi in rice (Wu et al, 2015). One AGO gene in fungus, Magnaporthe oryzae AGO2, interferes with RNAi likely by sequestering a broad range of siRNAs from MoAGO3 (Nguyen et al, 2018). Similarly, the data herein suggest that NbAGO10 could interfere with NbAGO1-mediated antiviral RNAi, possibly by competing with NbAGO1 for the binding of BaMV very small interfering (vsi)RNA (Fig.…”

“…). AtAGO10, OsAGO18 and MoAGO2 have been experimentally verified for their slicer activities in vitro (Ji et al ., ; Wu et al ., ; Nguyen et al ., ), whereas NbAGO10 has the potential to cleave the target transcripts because it contains the conserved slicer catalytic sites, the DDH motif (Fig. S5).…”