Molecular characterization of a novel umbra-like virus from Thuja orientalis (arborvitae) in South Korea

Belete, Mesele Tilahun; Kim, Se Eun; Kwon, Johnny; Igori, Davaajargal; Choi, Eung Kyoo; Hwang, Un Sun; Lee, Su-Heon; Moon, Jae Sun

doi:10.1007/s00705-023-05783-w

Cited by 6 publications

(1 citation statement)

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“…General time reversible model with gamma distribution rates and invariable frequency (GTR+G+I) was determined to be the best-fit substitution model in MEGA X and was implemented to construct the tree. The following ULV sequences were used: PMeV2 (KT921785), PpVQ (MT113180), BabVQ (MT113182) [ 42 , 93 , 94 ], OULV (MH579715, MT909563, MT909562) [ 44 ], FULV (MW480492, MW480492) [ 60 ], CY1 (JX101610) [ 40 ], CY2 (MT893741) [ 77 ], WULV (OK573479) [ 95 ], GULV(OP886321) [ 96 ], PIULV (OL330774) [ 97 ], SbaVa (MK211274) [ 98 ], TULV (OK018180) [ 99 ], MULV (OM937759) [ 41 ], JgULV (OM937760) [ 41 ], SULV (MN868593) [ 100 ], EMaV (MF415880), AgULV (OP660856), GPpTV1 (OM514399), ArULV (OQ102001) [ 101 ]. To analyze the phylogenetic relationship of ORF5 proteins with selected CPs and MPs, protein sequences were aligned using PROMALS3D [ 53 ] and trimmed in MEGA X.…”

Section: Methodsmentioning

confidence: 99%

Umbravirus-like RNA viruses are capable of independent systemic plant infection in the absence of encoded movement proteins

Ying,

Bera,

Liu

et al. 2024

PLoS Biol

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The signature feature of all plant viruses is the encoding of movement proteins (MPs) that supports the movement of the viral genome into adjacent cells and through the vascular system. The recent discovery of umbravirus-like viruses (ULVs), some of which only encode replication-associated proteins, suggested that they, as with umbraviruses that lack encoded capsid proteins (CPs) and silencing suppressors, would require association with a helper virus to complete an infection cycle. We examined the infection properties of 2 ULVs: citrus yellow vein associated virus 1 (CY1), which only encodes replication proteins, and closely related CY2 from hemp, which encodes an additional protein (ORF5CY2) that was assumed to be an MP. We report that both CY1 and CY2 can independently infect the model plant Nicotiana benthamiana in a phloem-limited fashion when delivered by agroinfiltration. Unlike encoded MPs, ORF5CY2 was dispensable for infection of CY2, but was associated with faster symptom development. Examination of ORF5CY2 revealed features more similar to luteoviruses/poleroviruses/sobemovirus CPs than to 30K class MPs, which all share a similar single jelly-roll domain. In addition, only CY2-infected plants contained virus-like particles (VLPs) associated with CY2 RNA and ORF5CY2. CY1 RNA and a defective (D)-RNA that arises during infection interacted with host protein phloem protein 2 (PP2) in vitro and in vivo, and formed a high molecular weight complex with sap proteins in vitro that was partially resistant to RNase treatment. When CY1 was used as a virus-induced gene silencing (VIGS) vector to target PP2 transcripts, CY1 accumulation was reduced in systemic leaves, supporting the usage of PP2 for systemic movement. ULVs are therefore the first plant viruses encoding replication and CPs but no MPs, and whose systemic movement relies on a host MP. This explains the lack of discernable helper viruses in many ULV-infected plants and evokes comparisons with the initial viruses transferred into plants that must have similarly required host proteins for movement.

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