Abstract
A fluorescent viral clone of the polerovirus Turnip yellows virus (TuYV) was engineered by introducing the Enhanced Green Fluorescent Protein (EGFP) sequence into the non-structural domain sequence of the readthrough protein, a minor capsid protein. The resulting recombinant virus, referred to as TuYV-RTGFP, was infectious in several plant species when delivered by agroinoculation and invaded efficiently non-inoculated leaves. As expected for poleroviruses, which infect only phloem cells, the fluorescence emitted by TuYV-RTGFP was restricted to the vasculature of infected plants. In addition, TuYV-RTGFP was aphid transmissible and enabled the observation of the initial sites of infection in the phloem after aphid probing in epidermal cells. The aphid-transmitted virus moved efficiently to leaves distant from the inoculation sites and importantly retained the EGFP sequence in the viral genome. This work reports on the first engineered member in the Luteoviridae family that can be visualized by fluorescence emission in systemic leaves of different plant species after agroinoculation or aphid transmission.
Highlights
Turnip yellows virus (TuYV, formerly BWYV-FL1) is a member of the Polerovirus genus in the Luteoviridae family
The readthrough domain (RTD) domain is involved in virus movement, not strictly mandatory, but is essential for aphid transmission [17,22,25]
The insertion of the fluorochrome sequence into a viral genome has always been a challenge since it can reduce the infectivity of the fluorescent virus or generate virus-deleted forms impaired in their ability to move systemically [57,58,59,60,61]
Summary
Turnip yellows virus (TuYV, formerly BWYV-FL1) is a member of the Polerovirus genus in the Luteoviridae family. Its single-stranded positive sense RNA genome of approximately 6 kb is encapsidated into isometric particles of 25 nm in diameter. TuYV has a wide host range among herbaceous plants and infects important crops such as oilseed rape [1]. The genome consists of seven interlocked and overlapping open reading frames (ORFs), which are expressed from the genomic and subgenomic RNAs by non-canonical translation mechanisms [2]. Members of the Luteoviridae are strictly restricted to the three cell types constituting the phloem; the nucleated phloem parenchyma cells and companion cells, where the virus replicates, and the sieve elements, which convey the virus to sites distant from the inoculation point [3,4,5,6].
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