Beyond Loading: Functions of Plant ARGONAUTE Proteins

Abstract

ARGONAUTE (AGO) proteins are key components of the RNA-induced silencing complex (RISC) that mediates gene silencing in eukaryotes. Small-RNA (sRNA) cargoes are selectively loaded into different members of the AGO protein family and then target complementary sequences to in-duce transcriptional repression, mRNA cleavage, or translation inhibition. Previous reviews have mainly focused on the traditional roles of AGOs in specific biological processes or on the molecular mechanisms of sRNA sorting. In this review, we summarize the biological significance of canonical sRNA loading, including the balance among distinct sRNA pathways, cross-regulation of different RISC activities during plant development and defense, and, especially, the emerging roles of AGOs in sRNA movement. We also discuss recent advances in novel non-canonical functions of plant AGOs. Perspectives for future functional studies of this evolutionarily conserved eukaryotic protein family will facilitate a more comprehensive understanding of the multi-faceted AGO proteins.

A novel ilarvirus protein CP-RT is expressed via stop codon readthrough and suppresses RDR6-dependent RNA silencing

“…AGOs incorporate siRNAs into RNAi effector complexes. Arabidopsis encodes 10 AGOs of which AGO1, AGO2, and to some extent AGO5 are the most important players in virus-induced RNAi [118][119][120]. The 5 0 nucleotide of siRNA determines its targeting into different AGO complexes, where AGO1 preferentially binds to siRNAs with a 5 0 -terminal U residue [121].…”