Fig. 3

Regulatory RNA-silencing cascade and activation of endogenous siRNAs during viral infection. a Schematic representation of the non-canonical Dicer-like 2 (DCL2)-derived miR6026 function in the cleavage of DCL2 mRNA and in triggering secondary siRNAs and silencing cascade processes. b Schematic representation of the canonical Dicer-like 1 (DCL1)-derived miR482 function in the cleavage of mRNAs, which code for nucleotide binding/leucine-rich repeat-type immune receptors, and in triggering secondary siRNAs and silencing cascade processes. c Schematic representation of the transmembrane receptor-associated kinases SOBIR1 and BAK1, and the immune repressor BIR1. BIR1 contributes to antiviral defense and undergoes post-transcriptional regulation mediated by virus-activated (va) BIR1-derived secondary RNAs upon viral infection. d Schematic representation of vsiRNA biogenesis and widespread fine tuning of genes involved in defense responses. Upon infection, plant-encoded RNA-depended RNA polymerase 1 (RDR1) is induced, and drives the production of double-stranded (ds) RNAs using transcript as templates. Plant endogenous dsRNAs are processed by the induced antiviral DCL2 and 4 into a pool of vsiRNAs. vsiRNAs program AGO1, 2 and 5 to cleave mRNAs from where they are originated, and trigger silencing cascade mechanisms. Arrows indicate positive regulation and blunt-ended bars indicate inhibition. Blunt-ended end bars indicate an inhibitory effect. Plasma membrane (PM)