title: Composite potato plants with transgenic roots on non-transgenic shoots: a model system for studying gene silencing in roots.
abstract: Composite potato plants offer an extremely fast, effective and reliable system for studies on gene functions in roots using antisense or inverted-repeat but not sense constructs for gene inactivation. Composite plants, with transgenic roots on a non-transgenic shoot, can be obtained by shoot explant transformation with Agrobacterium rhizogenes. The aim of this study was to generate composite potato plants (Solanum tuberosum) to be used as a model system in future studies on root-pathogen interactions and gene silencing in the roots. The proportion of transgenic roots among the roots induced was high (80-100%) in the four potato cultivars tested (Albatros, Desirée, Sabina and Saturna). No wild-type adventitious roots were formed at mock inoculation site. All strains of A. rhizogenes tested induced phenotypically normal roots which, however, showed a reduced response to cytokinin as compared with non-transgenic roots. Nevertheless, both types of roots were infected to a similar high rate with the zoospores of Spongospora subterranea, a soilborne potato pathogen. The transgenic roots of composite potato plants expressed significantly higher amounts of β-glucuronidase (GUS) than the roots of a GUS-transgenic potato line event. Silencing of the uidA transgene (GUS) was tested by inducing roots on the GUS-transgenic cv. Albatros event with strains of A. rhizogenes over-expressing either the uidA sense or antisense transcripts, or inverted-repeat or hairpin uidA RNA. The three last mentioned constructs caused 2.5-4.0 fold reduction in the uidA mRNA expression. In contrast, over-expression of uidA resulted in over 3-fold increase in the uidA mRNA and GUS expression, indicating that sense-mediated silencing (co-suppression) was not functional in roots. The results suggest that composite plants offer a useful experimental system for potato research, which has gained little previous attention.
authors.affiliation: Institute for Land Use, University of Rostock, Rostock, Germany.
authors.forename: Patricia
authors.initials: P
authors.lastname: Horn
authors.forename: Johanna
authors.initials: J
authors.lastname: Santala
authors.forename: Steen Lykke
authors.initials: SL
authors.lastname: Nielsen
authors.forename: Maja
authors.initials: M
authors.lastname: Hühns
authors.forename: Inge
authors.initials: I
authors.lastname: Broer
authors.forename: Jari P T
authors.initials: JP
authors.lastname: Valkonen
mesh_terms: D060054:Agrobacterium / Q000187:drug effects / Q000378:metabolism; D001593:Benzyl Compounds / Q000494:pharmacology; D020868:Gene Silencing; D017343:Genes, Plant; D005966:Glucuronidase / Q000378:metabolism; D008954:Models, Biological; D010641:Phenotype; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D018520:Plant Shoots / Q000187:drug effects / Q000502:physiology*; D030821:Plants, Genetically Modified; D056909:Plasmodiophorida / Q000187:drug effects; D011687:Purines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000187:drug effects / Q000235:genetics* / Q000469:parasitology; D014170:Transformation, Genetic / Q000235:genetics; D019076:Transgenes
chemical_list: D001593:Benzyl Compounds; D010937:Plant Growth Regulators; D011687:Purines; D012333:RNA, Messenger; D005966:Glucuronidase; C480551:benzylaminopurine