M.Sc Thesis

M.Sc StudentBanner Idit
SubjectEnhancing Host Resistance to the Parasitic Weed Orobanche
spp. through Induced Expression of the Sarcotoxin
IA Gene in Transgenic Plants
DepartmentDepartment of Biology
Supervisors PROFESSOR EMERITUS Shimon Gepstein
DR. Radi Aly


Control of parasitic weeds can be extremely difficult, costly or hazardous to the environment. While the potentially most effective approach to parasitic weed control- host resistance-remains an unrealized goal for most crops, we have developed a simple genetic engineering strategy for conferring host plant resistance to Orobanche. The approach is based on sarcotoxin IA, a cecropin-type antibacterial peptide. The sarcotoxin IA gene was linked to the hmg2 promoter, a defense related isogene of 3-hydroxy-methylglutaryl coenzyme A reductase that is induced in response to parasitization by the parasitic weed Orobanche aegyptiaca, and the construct was transformed into tobacco. Transgene integration into the plant genome was confirmed by PCR and DNA hybridization, and its expression was demonstrated by reverse transcriptase (RT)-PCR and immunoblot analysis. Transgenic tobacco plants expressing the sarcotoxin IA gene were grown either in polyethylene bags, where tubercle development can be visualized, or in pots containing soil inoculated with Orobanche aegyptiaca seeds. Results indicated strong inhibition of parasite growth. Most parasite tubercles attached to the transgenic plants turned necrotic and showed abnormal development compared to those on non- transformed plants. Our results indicate that the sarcotoxin IA produced by the host plant is selectively toxic to the parasite. In related studies the potential for protein movement from host to parasite was demonstrated. We hypothesize that the toxin exerts its effect in the parasite. This strategy is potentially superior to other parasite control methods in that it can be effective at a low cost for producers and safe for the environment.