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A neomorphic sgs3 allele stabilizing miRNA cleavage products reveals that SGS3 acts as a homodimer

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Elmayan, Taline | Adenot, Xavier | Gissot, Lionel | Lauressergues, Dominique | Gy, Isabelle | Vaucheret, Hervé

Edité par CCSD ; Wiley -

International audience. The putative RNA‐binding protein SUPPRESSOR OF GENE SILENCING 3 (SGS3) protects RNA from degradation before transformation into dsRNA by the RNA‐dependent RNA polymerase RDR6 during plant post‐transcriptional gene silencing and trans ‐acting small interfering (siRNA) pathways. In this study, we show that SGS3 acts as a homodimer, and that the point mutation sgs3‐3 impairs post‐transcriptional gene silencing in a dominant‐negative manner through the formation of SGS3/sgs3‐3 heterodimers. Unlike complete‐loss‐of‐function sgs3 mutants, which are impaired in the accumulation of both micro RNA‐directed TAS cleavage products and mature trans ‐acting siRNAs, the sgs3‐3 mutant overaccumulates TAS cleavage products and exhibits slightly reduced trans ‐acting siRNA accumulation. Together, these results suggest that sgs3‐3 is a neomorphic allele that shows increased RNA protective activity, resulting in decreased RNA processing by downstream post‐transcriptional gene silencing and trans ‐acting siRNA pathway components.

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