title: The resistance of sour orange to Citrus tristeza virus is mediated by both the salicylic acid and RNA silencing defence pathways.
abstract: Citrus tristeza virus (CTV) induces in the field the decline and death of citrus varieties grafted on sour orange (SO) rootstock, which has forced the use of alternative decline-tolerant rootstocks in affected countries, despite the highly desirable agronomic features of the SO rootstock. Declining citrus plants display phloem necrosis below the bud union. In addition, SO is minimally susceptible to CTV compared with other citrus varieties, suggesting partial resistance of SO to CTV. Here, by silencing different citrus genes with a Citrus leaf blotch virus-based vector, we have examined the implication of the RNA silencing and salicylic acid (SA) defence pathways in the resistance of SO to CTV. Silencing of the genes RDR1, NPR1 and DCL2/DCL4, associated with these defence pathways, enhanced virus spread and accumulation in SO plants in comparison with non-silenced controls, whereas silencing of the genes NPR3/NPR4, associated with the hypersensitive response, produced a slight decrease in CTV accumulation and reduced stunting of SO grafted on CTV-infected rough lemon plants. We also found that the CTV RNA silencing suppressors p20 and p23 also suppress the SA signalling defence, with the suppressor activity being higher in the most virulent isolates.
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: Neus
authors: N
authors: Gómez-Muñoz
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: Karelia
authors: K
authors: Velázquez
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: María Carmen
authors: MC
authors: Vives
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: Susana
authors: S
authors: Ruiz-Ruiz
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: José Antonio
authors: JA
authors: Pina
authors: Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, Valencia, 46022, Spain.
authors: Ricardo
authors: R
authors: Flores
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: Pedro
authors: P
authors: Moreno
authors: Instituto Valenciano de Investigaciones Agrarias (IVIA), Centro de Protección Vegetal y Biotecnología, Moncada, Valencia, 46113, Spain.
authors: José
authors: J
authors: Guerri
mesh_terms: D017790:Closterovirus / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000382:microbiology*; D034622:RNA Interference; D020156:Salicylic Acid / Q000494:pharmacology*
chemical_list: D020156:Salicylic Acid
keywords: CLBV; citrus decline; reverse genetics; salicylic acid signalling defence suppressor; viral vector