The unique dual targeting of AGO1 by two types of PRMT enzymes promotes phasiRNA loading in Arabidopsis thaliana

Abstract

Arginine / R methylation (R-met) of proteins is a widespread post-translational modification (PTM), deposited by a family of protein arginine / R methyl transferase enzymes (PRMT). Regulations by R-met are involved in key biological processes deeply studied in metazoan. Among those, post-transcriptional gene silencing (PTGS) can be regulated by R-met in animals and in plants. It mainly contributes to safeguard processes as protection of genome integrity in germlines through the regulation of piRNA pathw a y in metazoan, or response to bacterial infection through the control of AGO2 in plants. So far, only PRMT5 has been identified as the AGO / PIWI R-met writer in higher eukary otes. We unco v ered that AGO1, the main PTGS effector regulating plant de v elopment, contains unique R-met features among the AGO / PIWI superfamily, and outstanding in eukaryotes. Indeed, AGO1 contains both symmetric (sDMA) and asymmetric (aDMA) R-dimethylations and is dually targeted by PRMT5 and by another type I PRMT in Arabidopsis thaliana . We sho w ed also that loss of sDMA didn't compromise AtAGO1 subcellular trafficking in planta . Interestingly, we underscored that AtPRMT5 specifically promotes the loading of phasiRNA in AtAGO1. All our observations bring to consider this dual regulation of AtAGO1 in plant de v elopment and response to environment, and pinpoint the complexity of AGO1 post-translational regulation.