Pomoviruses associated with the rhizomania syndrome : a reverse genetic approach of the genome organization and multiplication requirements in planta
(2010)
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- Authors
- Supervisors
- Bragard, Claude
- Abstract
- (en) Beet soil-borne virus (BSBV) and Beet virus Q (BVQ) are frequently detected in sugar beet roots with the causal agent of the rhizomania syndrome, the Beet necrotic yellow vein virus (BNYVV). These viruses are vectored by the same soil-borne protist Polymyxa betae. While the pathogenicity of BNYVV needs no further proof, the role of BSBV and BVQ remains unclear. In addition, BSBV and BVQ pomoviruses have similar genomes composed of three single-stranded RNAs. However, the reported organization of BVQ RNA-2 differs from that of BSBV, encoding for a shorter putative read-through (RT) domain for the coat protein (CP). Two reverse genetic strategies were set up to tackle with the special organization of BVQ RNA-2 and the multiplication dynamics of BSBV and BVQ. In this view, ten BVQ strains from Europe were partially sequenced and full-length cDNA clones were constructed for both pomoviruses. On one hand, a common RT domain of 76 kilodalton (kDa) was described for the BVQ CP, instead of the 35 kDa one previously reported. Such RT domain was predicted to contain both transmembrane helices thought to be required for viral transmission, when only one is identified in the 35 kDa RT. RNA-2 rearrangements were found to be responsible for these major differences between naturally-occurring and laboratory-maintained strains. On the other hand, the behaviour of BSBV and BVQ transcripts from full-length cDNA clones was investigated in planta. Whereas the BSBV putative replicase (RNA-1) and movement proteins (RNA-3) proved to be necessary and sufficient for local infections, BVQ transcripts were not self-infectious. These were shown to rely on the simultaneous presence of BNYVV, but not BSBV, to multiply in Chenopodium quinoa leaves. Moreover, BSBV and BVQ structural proteins displayed unexpected migration patterns in SDS-PAGE conditions. This thesis revisited the BVQ genome organization and describes pioneer results in the field of sugar beet pomoviruses multiplication requirements. The BSBV and BVQ full-length cDNA clones open the way for studying their particular functioning and pathogenic impact on beet, alone or in combination with other soil-borne viruses.
- Affiliations
Citations
Crutzen, F. (2010). Pomoviruses associated with the rhizomania syndrome : a reverse genetic approach of the genome organization and multiplication requirements in planta. https://hdl.handle.net/2078.5/131070