The potato leafroll virus (PLRV) P0 protein (P0^PL) is a suppressor of RNA silencing. In this study, we showed that P0 protein from an Argentinian isolate of PLRV (P0^PL‐Ar) has an additional activity not described for other PLRV or P0 proteins from poleroviruses. Besides reporting that P0^PL‐Ar displays both local and systemic silencing suppressor activity, we demonstrated, for the first time, that P0^PL‐Ar impedes accumulation of dsRNA‐derived siRNAs. We also showed that P0^PL‐Ar interacts with Solanum tuberosum SKP1 orthologue (StSKP1) and triggers destabilization of ARGONAUTE 1 (AGO1) and that these actions are mediated by the F‐box‐like domain. A mutant in the GW/WG motif within the P0^PL‐Ar F‐box‐like motif lost the suppression activity, the interaction with StSKP1 and abolished AGO1 decay. Interestingly, a mutant in the L76/P77 residues within the P0^PL‐Ar F‐box‐like motif, which lost the suppression activity and the interaction with StSKP1, retained the capacity to enable AGO1 decay. Thus, unlike other P0 proteins of previously characterized poleroviruses, P0^PL‐Ar seems to have a dual activity, according to the findings of this study. This protein would act at both an upstream and a downstream step of the RNA silencing pathway: upstream of Dicer‐like enzyme (DCL)‐mediated primary siRNA production and downstream at the RNA‐induced silencing complex (RISC) complex level. Our results contribute to the understanding of the different ways PLRV P0 proteins function as silencing suppressors.

中文翻译：

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阿根廷马铃薯卷叶病毒P0蛋白：一种先前已知的抑制剂的新活性

马铃薯卷叶病毒（PLRV）P0蛋白（P0 ^PL）是RNA沉默的抑制剂。在这项研究中，我们显示了来自阿根廷PLRV分离株（P0 ^PL-Ar）的P0蛋白具有针对杆状病毒的其他PLRV或P0蛋白未描述的其他活性。除了报道P0 ^PL-Ar同时显示出局部和全身沉默抑制活性外，我们还首次证明P0 ^PL-Ar阻碍了dsRNA衍生的siRNA的积累。我们还证明了P0 ^PL‐Ar与马铃薯的相互作用SKP1直向同源物（StSKP1）并触发ARGONAUTE 1（AGO1）的不稳定，并且这些作用是由F-box-like域介导的。P0 ^PL-Ar F-box-like基序中GW / WG基序的一个突变体失去了抑制活性，与StSKP1的相互作用以及AGO1衰变的消失。有趣的是，P0 ^PL-Ar F-box-like基序内L76 / P77残基的突变体失去了抑制活性，并与StSKP1相互作用，保留了使AGO1衰减的能力。因此，与以前鉴定的杆状病毒的其他P0蛋白不同，P0 ^PL‐Ar根据这项研究的发现，它似乎具有双重活性。该蛋白将在RNA沉默途径的上游和下游步骤中起作用：Dicer样酶（DCL）介导的一级siRNA产生的上游，而在RNA诱导的沉默复合物（RISC）复杂水平的下游。我们的结果有助于理解PLRV P0蛋白作为沉默抑制剂的不同方式。