Abstract
Argonaute (AGO) proteins are core components of RNA interference (RNAi) but the mechanisms of their regulation, especially at the post-translational level, remain unclear. Among the ten AGOs in Arabidopsis, only AGO2 is induced by bacterial infection and is known to positively regulate immunity. Here we show that the N-terminal domain of AGO2 is enriched with arginine-glycine RG/GR repeats, which are methylated by protein arginine methyltransferase5 (PRMT5). Arginine methylation has dual functions in AGO2 regulation. Methylated arginine residues can promote AGO2 protein degradation and are also bound by Tudor-domain proteins (TSNs), which can degrade AGO2-associated small RNAs (sRNAs). PRMT5 is down-regulated during infection and the prmt5 mutant is more resistant to bacteria. We speculate that reduced PRMT5 expression during infection may lead to reduced arginine methylation of AGO2, resulting in accumulation of both AGO2 and, via reduced interaction with TSNs, accumulation of AGO2-associated sRNAs, to promote plant immunity. These results reveal that both the arginine methylation writer (PRMT5) and readers (TSNs) can regulate AGO2-mediated RNAi.
Highlights
Argonaute (AGO) proteins are core components of RNA interference (RNAi) but the mechanisms of their regulation, especially at the post-translational level, remain unclear
We identified 70 AGO2-associated proteins that were only associated with pAGO2:3HA:AGO2 but not with pAGO7:gus, by using the label-free quantification (LFQ) intensity value (Supplementary Data 1)
protein arginine methyltransferase5 (PRMT5) catalyzes the formation of monomethylarginine (MMA) and symmetric dimethylarginine, which is involved in regulating many animal developmental and pathological processes[28,37]
Summary
Argonaute (AGO) proteins are core components of RNA interference (RNAi) but the mechanisms of their regulation, especially at the post-translational level, remain unclear. Among the ten AGOs in Arabidopsis, only AGO2 is induced by bacterial infection and is known to positively regulate immunity. We speculate that reduced PRMT5 expression during infection may lead to reduced arginine methylation of AGO2, resulting in accumulation of both AGO2 and, via reduced interaction with TSNs, accumulation of AGO2-associated sRNAs, to promote plant immunity. These results reveal that both the arginine methylation writer (PRMT5) and readers (TSNs) can regulate AGO2-mediated RNAi. Microbial pathogens cause detrimental and deadly human and animal diseases, as well as severe yield losses in crop plants[1,2,3]. We demonstrate that arginine methylation can regulate both AGO2 protein stability and AGO2 interaction with Tudor-domain proteins (TSNs) that can regulate accumulation of AGO2-associated sRNAs
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