Submitted to: Virus Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/2000
Publication Date: N/A
Citation: Interpretive Summary: Plum pox virus is the most serious virus disease of stone fruits (peach,nectarine, plum, apricot, cherry). This virus causes fruit to be deformed and to drop from the tree before ripening. We have used genetic engineering to insert a virus resistance gene into plum & we have developed a genetically engineered line that is resistant to virus infection in greenhouse studies. Our most recent information based on field studies in Europe indicates that the genetically engineered line is resistant to natural infection that is caused by insects that carry the virus from plant to plant. We are studying the expression of the transgenes in these genetically engineered plums to see when (fall, winter, spring, summer) and where (leaves, stems, roots, fruit) they are turned on. This information will lead to improved control of the expression of bioengineered genes in transgenic tree fruits and to specifically targeted control of the virus.
Technical Abstract: Sharka or plum pox (ppv) is the most serious disease of Prunus. Our program is aimed at the development of a biotechnological approach to PPV control that is effective and is proven to be environmentally safe. Our program began with the cloning of the PPV coat protein (CP) gene & the development of a plum (Prunus domestica) transformation system. The CP construct was first tested in Nicotiana benthamiana & in this system proved effective in producing transgenic plants with varying levels of CP expression. Based on these results plums were transformed by Agrobacterium tumefaciens system. Transgenic plum lines were bud-graft inoculated with PPV in greenhouse. One line, C-5, proved to be highly resistant. This line contained multiple copies of the insert, produced low levels of PPV CP mRNA, no detectable CP and the insert appeared to be methylated. These characteristics all suggest that the resistance of the C-5 clone is based on posttranscriptional gene silencing (PTGS). Field tests of C-5 and other transgenic lines in Poland Romania & Spain have demonstrated that C-5 exposed to natural infection for 3 years have not become infected while control trees were infected in the first year. Research on the biorisk of PPV CP transgenic plants is in progress.