title: Post-transcriptional gene silencing of the p23 silencing suppressor of Citrus tristeza virus confers resistance to the virus in transgenic Mexican lime.
abstract: Previously, we have shown that most Mexican limes (Citrus aurantifolia (Christ.) Swing.) expressing the p23 gene of Citrus tristeza virus (CTV) exhibit aberrations resembling viral leaf symptoms. Here we report that five independent transgenic lines having normal phenotype displayed characteristics typical of post-transcriptional gene silencing (PTGS): multiple copies of the transgene, low levels of the corresponding mRNA, methylation of the silenced transgene, and accumulation of p23-specific small interfering RNAs (siRNAs). When graft- or aphid-inoculated with CTV, some propagations of these silenced lines were immune: they neither expressed symptoms nor accumulated virions and viral RNA as estimated by DAS-ELISA and Northern blot hybridization, respectively. Other propagations were moderately resistant because they became infected later and showed attenuated symptoms compared to controls. The susceptible propagations, in addition to symptom expression and elevated virus titer, accumulated p23-specific siRNAs at levels significantly higher than immune or non-inoculated propagations, and showed transgene demethylation. This variable response among clonal transformants indicates that factors other than the genetic background of the transgenic plants play a key role in PTGS-mediated resistance.
authors.affiliation: Instituto Valenciano de Investigaciones Agrarias (IVIA), Apdo. Oficial, Moncada, 46113 Valencia, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Fagoaga
authors.forename: Carmelo
authors.initials: C
authors.lastname: López
authors.forename: Alfonso Hermoso
authors.initials: AH
authors.lastname: de Mendoza
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: D015152:Blotting, Northern; D015139:Blotting, Southern; D017790:Closterovirus / Q000235:genetics*; D019175:DNA Methylation; D020868:Gene Silencing; D030821:Plants, Genetically Modified; D012323:RNA Processing, Post-Transcriptional; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics*; D019076:Transgenes; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D014764:Viral Proteins; C407248:p23 protein, Citrus tristeza virus