Molecular determinants of plant antiviral defence
RNA silencing or interference is a regulatory mechanism of gene expression mediated by small RNAs (sRNAs). In plants, sRNAs control important developmental and reproductive processes as well as adaptive responses to biotic and abiotic stresses. In addition, they confer protection against virus infection. Over the past years, considerable efforts have led to the elucidation of this vital regulatory pathway. ARGONAUTES (AGOs) are one of the main components of the pathway, comprising the RNA-induced silencing complex (RISC). RISC silences target genes at the chromatin or at the mRNA level. In Arabidopsis thaliana, AGO1 is the main effector protein associated to microRNAs and small interfering RNAs. However, little information is available regarding the modulation of AGO1 activity at the protein level. Scientists on the EU-funded AGOIM (Characterization of the interactions and modifications affecting AtAGO1 function) set out to investigate the post-translational modifications of AGO1 and protein-protein interactions that could influence its function. Their work mainly concentrated on the methylation state of the protein at arginine residues and the identification of putative AGO1 interaction partners. Scientists replaced the amino acids that normally get methylated in AGO1 and observed no major effects on plant physiology. However, they isolated proteins within the RISC complex that might require AGO1 methylation for protein-protein interaction. Additionally, they identified putative AGO1 interactors that might be involved in different aspects of RNA silencing biology, such as the production of endogenous sRNAs. Moreover, the impact of TUDOR-SN proteins on AGO1 function was investigated. Taken together, the findings of the AGOIM project provide significant insight into the mechanism of RNA silencing in plants. This information could help develop new approaches to combat virus infection or tools that allow plant physiology modulation via RNA silencing.
Keywords
Plant, antiviral defence, RNA silencing, AGO, RISC complex, AGO1
