title: Accumulation of transgene-derived siRNAs is not sufficient for RNAi-mediated protection against Citrus tristeza virus in transgenic Mexican lime.
abstract: Mexican lime plants transformed with the 3'-terminal 549 nucleotides of the Citrus tristeza virus (CTV) genome in sense, antisense and intron-hairpin formats were analysed for transgene-derived transcript and short interfering RNA (siRNA) accumulation, and for CTV resistance. Propagations from all sense, antisense and empty-vector transgenic lines were susceptible to CTV, except for a single sense-line plant with a complex transgene integration pattern that showed transgene-derived siRNAs in association with low levels of the transgene-derived transcript. In contrast, nine of 30 intron-hairpin lines showed CTV resistance, with 9%-56% of bud-propagated plants, depending on the line, remaining uninfected on graft inoculation, and the others being susceptible. Although resistance was always associated with the presence of transgene-derived siRNAs, their level in different sense and intron-hairpin transformants was variable irrespective of the response to CTV infection. In intron-hairpin lines with single transgene integration, CTV resistance was correlated with low accumulation of the transgene-derived transcript rather than with high accumulation of transgene-derived siRNAs.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, Valencia 46022, Spain.
authors.forename: Carmelo
authors.initials: C
authors.lastname: López
authors.forename: Magdalena
authors.initials: M
authors.lastname: Cervera
authors.forename: Carmen
authors.initials: C
authors.lastname: Fagoaga
authors.forename: Pedro
authors.initials: P
authors.lastname: Moreno
authors.forename: Luis
authors.initials: L
authors.lastname: Navarro
authors.forename: Ricardo
authors.initials: R
authors.lastname: Flores
authors.forename: Leandro
authors.initials: L
authors.lastname: Peña
mesh_terms: D020413:3' Untranslated Regions; D001483:Base Sequence; D002957:Citrus / Q000821:virology*; D017931:DNA Primers; D018076:DNA, Complementary; D007438:Introns; D016366:Open Reading Frames; D010942:Plant Viruses / Q000502:physiology*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D034741:RNA, Small Interfering; D014170:Transformation, Genetic; D019076:Transgenes
chemical_list: D020413:3' Untranslated Regions; D017931:DNA Primers; D018076:DNA, Complementary; D034741:RNA, Small Interfering