Silencing small RNAs (sRNAs) are important regulatory molecules involved in the most diverse aspects of plant physiology, including development, response to biotic and abiotic stresses, genome stability and also defense against pathogens. sRNA originate from double-strand RNAs (dsRNAs), which are processed by DICER LIKE enzymes (DCLs) to 19-24 nucleotide long sRNAs. These molecules are then loaded into ARGONAUTE (AGO) proteins to form the RNA-induced silencing complex (RISC), which drives gene silencing either at the transcriptional or post-transcriptional level. In the model plant Arabidopsis thaliana AGO1 is the main effector of microRNAs (miRNAs) and many distinct classes of small interfering RNAs (siRNAs), including those involved in antiviral defense. Despite its importance in plant biology and defense, not much is known about the post-translational modifications and protein interactors affecting AGO1 function. In an effort to better understand the regulation of AGO1-dependent sRNA pathways, the host laboratory has identified several putative AGO1 interacting proteins, among them, heat shock proteins (HSP70s) and TSN1/2, two tudor-domain proteins, which seem to strongly aggregate onto AGO1 upon virus infections, suggesting their roles in antiviral silencing. In addition, the host laboratory has confirmed that AGO1 can be Arginine methylated, a modification with potentially important implications for the correct function, stability or localization of the protein. The main goal of this research application is to characterize the role of TSN in the AGO1-RISC complex, during healthy growth and virus infections. It also aims at understanding the potential protective role of HSP70s for AGO1, and the consequences of AGO1 methylation for sRNA-directed regulations.