Interaction between Brassica yellows virus silencing suppressor P0 and plant SKP1 facilitates stability of P0 in vivo against degradation by proteasome and autophagy pathways

Abstract

Summary P0 protein of some polerovirus members can target ARGONAUTE 1 ( AGO 1) to suppress RNA silencing. Although P0 harbors an F‐box‐like motif reported to be essential for interaction with S phase kinase‐associated protein 1 ( SKP 1) and RNA silencing suppression, it is the autophagy pathway that was shown to contribute to AGO 1 degradation. Therefore, the role of P0– SKP 1 interaction in silencing suppression remains unclear. We conducted global mutagenesis and comparative functional analysis of P0 encoded by Brassica yellows virus (BrYV) (P0 Br ). We found that several residues within P0 Br are required for local and systemic silencing suppression activities. Remarkably, the F‐box‐like motif mutant of P0 Br , which failed to interact with SKP 1, is destabilized in vivo . Both the 26S proteasome system and autophagy pathway play a role in destabilization of the mutant protein. Furthermore, silencing of a Nicotiana benthamiana SKP 1 ortholog leads to the destabilization of P0 Br . Genetic analyses indicated that the P0 Br – SKP 1 interaction is not directly required for silencing suppression activity of P0 Br , but it facilitates stability of P0 Br to ensure efficient RNA silencing suppression. Consistent with these findings, efficient systemic infection of Br YV requires P0 Br . Our results reveal a novel strategy used by BrYV for facilitating viral suppressors of RNA silencing stability against degradation by plant cells.

Investigation of the effects of P1 on HC-Pro-mediated gene silencing suppression through genetics and omics approaches

“…P1/HC-Pro of TuMV speci cally primes posttranslational AGO1 degradation AGO1 degradation has been reported to be controlled by selective autophagy (Kobayashi et al, 2019;Li et al, 2019;Michaeli et al, 2019). The P0 viral suppressor of Polerovirus is thought to trigger autophagic AGO1 degradation (Michaeli et al, 2019).…”

Investigation of the Effects of P1 on Hc-Pro-Mediated Gene Silencing Suppression Through Genetics and Omics Approaches

“…AGO1 degradation has been reported to be controlled by selective autophagy (Kobayashi et al 2019;Li et al 2019;Michaeli et al 2019). The P0 viral suppressor of Polerovirus is thought to trigger autophagic AGO1 degradation (Michaeli et al 2019).…”

Functional Characterization of RNA Silencing Suppressor P0 from Pea Mild Chlorosis Virus

“…The poleroviruses are distributed worldwide, infecting many crops of economic importance and causing severe plant diseases and yield losses. As previously reported, P0 proteins of several poleroviruses suppress RNA silencing [33,[35][36][37][38][39][40][41][42][43][44][45][46][47]. Although P0 proteins have a very low amino acid sequence identity, they have a conserved F-box-like motif [LPxx(L/I)x 10-13 P] in the N-terminal region and conserved residues [(K/R)IYGEDGX 3 FWR] in the C-terminal region [35,40].…”