Function and diversity of P0 proteins among cotton leafroll dwarf virus isolates

Abstract

BackgroundThe RNA silencing pathway is an important anti-viral defense mechanism in plants. As a counter defense, some members of the viral family Luteoviridae are able to evade host immunity by encoding the P0 RNA silencing suppressor protein. Here we explored the functional diversity of P0 proteins among eight cotton leafroll dwarf virus (CLRDV) isolates, a virus associated with a worldwide cotton disease known as cotton blue disease (CBD).MethodsCLRDV-infected cotton plants of different varieties were collected from five growing fields in Brazil and their P0 sequences compared to three previously obtained isolates. P0’s silencing suppression activities were scored based on transient expression experiments in Nicotiana benthamiana leaves.ResultsHigh sequence diversity was observed among CLRDV P0 proteins, indicating that some isolates found in cotton varieties formerly resistant to CLRDV should be regarded as new genotypes within the species. All tested proteins were able to suppress local and systemic silencing, but with significantly variable degrees. All P0 proteins were able to mediate the decay of ARGONAUTE proteins, a key component of the RNA silencing machinery.ConclusionsThe sequence diversity observed in CLRDV P0s is also reflected in their silencing suppression capabilities. However, the strength of local and systemic silencing suppression was not correlated for some proteins.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-015-0356-7) contains supplementary material, which is available to authorized users.

A Suppressor Screen for AGO1 Degradation by the Viral F-Box P0 Protein Uncovers a Role for AGO DUF1785 in sRNA Duplex Unwinding

“…At present, it is still unclear how the F-box protein P0 interacts with the identified AGO1 degron, and we cannot exclude the possibility that this interaction also involves a specific posttranslational modification and/or requirement for an additional factor. Notably, P0 proteins from different viruses lack sequence similarities and no defined structure or protein domain could be predicted, though most of them are able to mediate the decay of AGOs (Fusaro et al, 2012;Almasi et al, 2015;Cascardo et al, 2015). Because mutation of the P0 F-box motif impaired the interaction with AGO1 ( Figure 3A), it is likely that P0 is folded to recognize AGOs only in the context of an assembled SCF.…”

P0 protein of cotton leafroll dwarf virus‐atypical isolate is a weak RNA silencing suppressor and the avirulence determinant that breaks the cotton Cbd gene‐based resistance

“…P0 CL‐at protein has an amino acid point mutation in the F‐box‐like motif, where the isoleucine (I) at position 72 is replaced by a valine (V) (Agrofoglio et al ., ). Interestingly, three resistance‐breaking CLRDV isolates from Brazil (Acr9, Ima2 and Ipa4) present the same amino acid point mutation in the F‐box‐like motif as P0 CL‐at and were characterized as weaker VSRs than Brazilian P0 CL (Cascardo et al ., ).…”

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

“…P0 protein of Turnip yellows virus (TuYV), also known as Beet western yellows virus isolate FL1 (BWYV-FL1), is the first VSR reported in the genus polerovirus (Pazhouhandeh et al, 2006). In recent several years, P0 proteins from various poleroviruses have been shown to function as VSRs (Pazhouhandeh et al, 2006;Mangwende et al, 2009;Csorba et al, 2010;Han et al, 2010;Kozlowska-Makulska et al, 2010;Delfosse et al, 2014;Zhuo et al, 2014;Almasi et al, 2015;Cascardo et al, 2015;Chen et al, 2016). Several regions within P0 are essential for their silencing suppression activity, including a consensus F-box-like motif (LPXX(L/I)X 10-13 P) and the Phe/Trp (FW) residues within the C-terminal consensus sequence ((K/R) IYGED GX 3 FWR) (Pazhouhandeh et al, 2006;Bortolamiol et al, 2007;Mangwende et al, 2009;Han et al, 2010;Fusaro et al, 2012;Delfosse et al, 2014;Zhuo et al, 2014;Almasi et al, 2015;Chen et al, 2016).…”