Development of Transgenic Plums Using a siRNA Construct for Improving Plum Pox Virus Resistance

Plum pox virus (PPV) is one of the most serious pathogens affecting stone fruits. This virus is the causal agent of “sharka disease” and mainly infects apricot, peach and plum. Sharka has been reported of worldwide distribution, highlighting the Mediterranean Europe and The United States areas as hot-spots. In Chile, PPV infection was first described in 1994 and the specific isolate Diderot (PPV-D) was first characterized in 1996. Among the multiple strategies to fight the disease, post transcriptional gene silencing (PTGS) has been by far, the most successful one. Thein vivo generation of double-stranded RNA hairpin structures as inducers of specific gene silencing was described in 2003. Since then, the use of "hairpin small interfering RNAs" (or hsiRNA) has made possible the degradation of a target RNA (i.e., the viral coat protein), allowing the generation of virus-resistant plant lines. In 2009, we described thesuccessful establishment and improvement of a genetic transformation platform for Prunus spp. using Japanese plum as a model; in this work, we present the generation and evaluation of several transgenic plum lines, genetically modified with a hsiRNA construct (PPV-iRNA) directed to silence highly sensitive regions of the PPV coat protein gene that were arranged in tandem. The obtained GM plants were grafted onto PPV-D infected Adesoto-101 (Prunus insititia) plants. Results, based on the analysis of plants symptomatology and virus loads measured by ELISA and qRT-PCR, allowed us to define two resistant plum lines against the virus after two seasons of evaluations.

This work is funded by the following Programs: INIA(Chile)-CSIC 501646-70, BIOFRUTALES Consortium, and FONDEF-CHILE G09I1008