Experimental and bioinformatic evidence that raspberry leaf blotch emaravirus P4 is a movement protein of the 30K superfamily

Abstract

Emaravirus is a recently described genus of negative-strand RNA plant viruses. Emaravirus P4 protein localizes to plasmodesmata, suggesting that it could be a viral movement protein (MP). In the current study, we showed that the P4 protein of raspberry leaf blotch emaravirus (RLBV) rescued the cell-to-cell movement of a defective potato virus X (PVX) that had a deletion mutation in the triple gene block 1 movement-associated protein. This demonstrated that RLBV P4 is a functional MP. Sequence analyses revealed that P4 is a distant member of the 30K superfamily of MPs. All MPs of this family contain two highly conserved regions predicted to form b-strands, namely b1 and b2. We explored by alanine mutagenesis the role of two residues of P4 (Ile106 and Asp127) located in each of these strands. We also made the equivalent substitutions in the 29K MP of tobacco rattle virus, another member of the 30K superfamily. All substitutions abolished the ability to complement PVX movement, except for the I106A substitution in the b1 region of P4. This region has been shown to mediate membrane association of 30K MPs; our results show that it is possible to make non-conservative substitutions of a well-conserved aliphatic residue within b1 without preventing the membrane association or movement function of P4.

An Eriophyid Mite-Transmitted Plant Virus Contains Eight Genomic RNA Segments with Unusual Heterogeneity in the Nucleocapsid Protein

“…The P4 proteins of FMV and RLBV have been demonstrated to be involved in cell-to-cell movement (39,40). Based on sequence homology with other emaraviral P4 proteins, it is likely that the P4 of WMoV might also be involved in cell-to-cell movement.…”

Deep sequencing of dsRNAs recovered from mosaic-diseased pigeonpea reveals the presence of a novel emaravirus: pigeonpea sterility mosaic virus 2

“…A database search showed the highest identity of this polypeptide with those encoded by RNA4 of FMV (75 %) and RRV (61.2 %) ( Table 2). The SLP-Local (Subcellular Location Predictor) program predicted the expression product of RNA4 to be a possible membrane-located protein lacking the transmembrane helices that are likely to be involved in virus cell-to-cell movement, similar to comparable movement proteins encoded by FMV, PPSMV-1, RLBV, WMoV and RRV RNA4 [8,9,15,31,40,42]. However, this segment contained a conserved motif (FDPNFQQFITGSL 148-160 ), whose function is unknown.…”

Subcellular localization of p29, a putative movement protein of pepper ringspot virus

“…2b). This result suggested that p29 associated with PD similarly to other viral MPs [44,[49][50][51][52][53]. Therefore, it was concluded that the p29 protein is most likely involved in the cell-to-cell movement of PepRSV.…”

“…Moderately conserved sequences ( Fig. 1, blue boxes) were also seen throughout the MPs, with high similarity scores (by aa change within the same aa class) [34,35,44]. The 30K superfamily MPs contain two hydrophobic regions that form an a-helix structure (aa 61-80 and 148-167, Fig.…”