| Popis: |
This study shows that 11 Arabidopsis thaliana ecotypes are susceptible to infection by two agronomically significant viruses of the genus Polerovirus. All ecotypes tested were, to varying degrees, susceptible to Beet mild yellowing virus (BMYV) and Turnip yellows virus (TuYV) though a closely related species, Beet chlorosis virus (BChV), was unable to establish detectable infection. Agrobacterium tumefaciens was used to transform A. thaliana with one of four constructs containing sequences corresponding to either the BMYV major capsid protein (CP) or putative movement protein (MP) genes in either full-length or 3’-truncated form. BMYV-derived sequences were under the constitutive Cauliflower mosaic virus 35S promoter and linked to the hpt (hygromycin resistance) gene. T1 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 CP and MP 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 T2 generation plants revealed four lines that displayed resistance; three harbouring the truncated CP construct and one carrying the truncated MP 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. A. thaliana 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. |
