Genetic transformation of sweet orange with the coat protein gene of Citrus psorosis virus and evaluation of resistance against the virus.
Citrus psorosis is a serious viral disease affecting citrus trees in many countries. Its causal agent is Citrus psorosis virus (CPsV), the type member of genus Ophiovirus. CPsV infects most important citrus varieties, including oranges, mandarins and grapefruits, as well as hybrids and citrus relatives used as rootstocks. Certification programs have not been sufficient to control the disease and no sources of natural resistance have been found. Pathogen-derived resistance (PDR) can provide an efficient alternative to control viral diseases in their hosts. For this purpose, we have produced 21 independent lines of sweet orange expressing the coat protein gene of CPsV and five of them were challenged with the homologous CPV 4 isolate. Two different viral loads were evaluated to challenge the transgenic plants, but so far, no resistance or tolerance has been found in any line after 1 year of observations. In contrast, after inoculation all lines showed characteristic symptoms of psorosis in the greenhouse. The transgenic lines expressed low and variable amounts of the cp gene and no correlation was found between copy number and transgene expression. One line contained three copies of the cp gene, expressed low amounts of the mRNA and no coat protein. The ORF was cytosine methylated suggesting a PTGS mechanism, although the transformant failed to protect against the viral load used. Possible causes for the failed protection against the CPsV are discussed.
Zanek
María Cecilia
MC
Facultad de Ciencias Exactas, Instituto de Bioquímica y Biología Molecular (IBBM), U.N.L.P., Calles 47 y 115, 1900, La Plata, Argentina. mczanek@biol.unlp.edu.ar
Reyes
Carina Andrea
CA
Cervera
Magdalena
M
Peña
Eduardo José
EJ
Velázquez
Karelia
K
Costa
Norma
N
Plata
Maria Inés
MI
Grau
Oscar
O
Peña
Leandro
L
García
María Laura
ML
D015152:Blotting, Northern; D015139:Blotting, Southern; D036022:Capsid Proteins / Q000235:genetics*; D002957:Citrus / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D004797:Enzyme-Linked Immunosorbent Assay; D007113:Immunity, Innate / Q000235:genetics; D008957:Models, Genetic; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D010942:Plant Viruses / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D010957:Plasmids / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014170:Transformation, Genetic / Q000235:genetics*
D036022:Capsid Proteins
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