Bioinformatic and mutational analysis of ophiovirus movement proteins, belonging to the 30K superfamily

Abstract

Ophioviridae is a family of segmented, negative-sense, single-stranded RNA plant viruses. We showed that their cell-to-cell movement protein (MP) is an isolated member of the 30K MP superfamily with a unique structural organization. All 30K MPs share a core domain that contains a nearly-invariant signature aspartate. We examined its role in the MP of Citrus psorosis virus (CPsV) and Mirafiori lettuce big-vein virus (MiLBVV). Alanine substitution of this aspartate prevented plasmodesmata accumulation of MP(MiLBVV), while MP(CPsV) was not affected. The capacity of ophiovirus MPs to increase the plasmodesmata size exclusion limit and non-cell autonomous protein feature was abolished in both mutants. To investigate the role of the signature aspartate in cell-to-cell movement, we constructed a new movement-deficient Tobacco mosaic virus vector used for trans-complementation assays. We showed that both ophiovirus MP mutants lack the cell-to-cell movement capacity, confirming that this signature aspartate is essential for viral cell-to-cell movement.

The first phlebo‐like virus infecting plants: a case study on the adaptation of negative‐stranded RNA viruses to new hosts

“…S4, see Supporting Information). Interestingly, the MPs of several ophioviruses, including CPsV, have been shown recently to belong to the 30K superfamily (Borniego et al , ; Mushegian and Elena, ). In addition, ML phylogenetic analyses with the MP of representative nsRNA viruses infecting plants showed that CCGaV p46 is clustered together with the MPs of ophioviruses (Fig.…”

Citrus Psorosis Virus Movement Protein Contains an Aspartic Protease Required for Autocleavage and the Formation of Tubule-Like Structures at Plasmodesmata

“…4Bii and iii). The identified region in MP CPsV contains an aspartic residue (D), which is also the first amino acid of an amino acid triad that is strictly conserved among ophiovirus MPs (45). This finding suggests that MP CPsV and other ophiovirus MPs have an autocatalytic protein cleavage activity.…”

“…Given that MP CPsV :GFP, but not GFP:MP CPsV , is capable of forming tubules at PD, we wondered whether this has functional relevance in virus movement. Since an infectious cDNA clone of CPsV to test this hypothesis by a reverse genetic approach is not available, we used an alternative assay to evaluate this activity (45,46). In this assay, we analyzed the capacities of MP CPsV :GFP and GFP:MP CPsV to trans-complement TMVΔMPΔCP-GFP, a previously reported movement-deficient TMV derivative (45).…”

“…Since an infectious cDNA clone of CPsV to test this hypothesis by a reverse genetic approach is not available, we used an alternative assay to evaluate this activity (45,46). In this assay, we analyzed the capacities of MP CPsV :GFP and GFP:MP CPsV to trans-complement TMVΔMPΔCP-GFP, a previously reported movement-deficient TMV derivative (45). Highly diluted Agrobacterium cultures harboring the TMVΔMPΔCP-GFP-encoding plasmid were infiltrated together with cultures for the expression of either MP CPsV :GFP, GFP:MP CPsV , or GFP as a negative control.…”

“…RNA 1 encodes a 280-kDa replicase (42) as well as a 24-kDa protein that affects microRNA (miRNA) maturation (43) and has RNA silencing-suppressing activity (44). RNA 2 encodes a protein of 54 kDa (named here MP CPsV ), which displays several features of a MP (45,46) and has RNA silencingsuppressing activity as well (44). RNA 3 encodes a CP of 48 kDa (47).…”