ARS | Publication request: Field plot assessments demonstrate that transgenic plums expressing Plum pox virus (PPV) coat protein gene do not affect the PPV strain composition or produce PPV recombinants

Submitted to: Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 14, 2010
Publication Date: July 12, 2011
Citation: Zagrai, L., Ravelonandro, M., Gaboreanu, I., Ferencz, B., Scorza, R., Zagrai, L., Pamfil, D., Popescu, O., Kelemen, B. 2011. Field plot assessments demonstrate that transgenic plums expressing Plum pox virus (PPV) coat protein gene do not affect the PPV strain composition or produce PPV recombinants. Journal of Plant Pathology. 93(1):159-165.

Interpretive Summary: Genetic engineering (GE) for the control of plant virus diseases has proven to be an effective technology. GE has been used to produce high levels of resistance to Plum pox virus (PPV) in plum. This disease has devastated plum production in Europe and is moving worldwide including the U.S. There are few useful natural sources of resistance. Genetic engineering using a small piece of the virus for providing an immune response in plums has been shown to be highly effective and safe. Resistant plums generally act by inducing a native plant defense response and the inserted genes themselves do not produce a product. Some forms of resistance could be developed that express resistance by producing a small piece of RNA similar to viral RNA produced by the pathogen. Some researchers have speculated that this resistance mechanism could lead to the development of new virus strains. This report shows that under field conditions for growing plums no new virus strains were produced in GE plants that produce a small piece of viral RNA. This study confirms earlier work that also found that no new virus strains were produced in plantings of GE plums expressing viral gene pieces. The current research not only shows that these RNA-producing plums are environmentally safe but also shows that the resistant plums that do not produce detectable RNA are safe.

Technical Abstract: The serological and molecular variability of Plum pox virus (PPV) detected in transgenic plum trees harboring PPV capsid gene versus those found in conventional plums were analyzed. Strain characterization was serologically determined by TAS-ELISA using PPV-D and PPV-M specific monoclonal antibodies and by molecular typing. Molecular typing across three genomic regions corresponding to (Cter)CP, (Cter)NIb - (Nter)CP - CI and RFLP analysis at the C-ter of CP cistron verified the occurrence of different PPV strains. PCR products spanning (Cter)CP and (Cter)NIb - (Nter)CP regions were sequenced and revealed that there was no significant difference between PPV isolates collected from susceptible transgenic and conventional plums. TAS-ELISA using PPV-D and PPV-M specific moloclonal antibodies and molecular typing suggest that the transgenic plums released in the field do not represent an environmental risk through the emergence of new PPV variants.