This study shows that 11 <i>Arabidopsis thaliana</i> ecotypes are susceptible to infection by two agronomically significant viruses of the genus <i>Polerovirus</i>. All ecotypes tested were, to varying degrees, susceptible to <i>Beet mild yellowing virus </i>(BMYV) and <i>Turnip yellows virus </i>(TuYV) though a closely related species, <i>Beet chlorosis virus </i>(BChV), was unable to establish detectable infection. <i>Agrobacterium tumefaciens </i>was used to transform <i>A. thaliana </i>with one of four constructs containing sequences corresponding to either the BMYV major capsid protein (<i>CP</i>) or putative movement protein (<i>MP</i>) genes in either full-length or 3’-truncated form. BMYV-derived sequences were under the constitutive <i>Cauliflower mosaic virus </i>35S promoter and linked to the <i>hpt</i> (hygromycin resistance) gene. T<sub>1</sub> plants were identified by selection on hygromycin and the presence of the viral gene sequences confirmed by PCR. Plants carrying full-length gene constructs were recovered with low frequency and exhibited abnormal phenotypic effects. Transgenic plants harbouring truncated <i>CP </i>and <i>MP</i> gene sequences arose with greater frequency; 16 and 12 independent lines were respectively identified. Primary transformants were grown to maturity under glasshouse conditions and allowed to self-pollinate. Analysis of T<sub>2 </sub>generation plants revealed four lines that displayed resistance; three harbouring the truncated <i>CP</i> construct and one carrying the truncated <i>MP</i> construct. Resistance was manifest as an amelioration of BMYV-induced symptoms and decreased susceptibility to disease correlated with decreased BMYV accumulation, as demonstrated by ELISA. <i>A. thaliana </i>has been established as a valuable model system with which to assess virus-derived transgenes for functionality. With respect to advances in transgenic design, which may afford protected plants effective viral immunity, a future strategy for engineering BMYV resistance is proposed. The prospects for commercial exploitation of pathogen-derived resistance technology by the sugar beet industry are also discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:599213 |
| Date | January 2005 |
| Creators | Freeman, B. D. C. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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