Environment risk assessment of transgenic Nicotiana tabacum: Assessing non-target effects of bioreactor crops

Plants have great potential as bioreactors for the large-scale production of various high-value recombinant proteins, such as vaccines, antibodies and biopharmaceutical. To be successful molecular farming must increase recombinant protein yields and address biosafety issues. Screening insect herbivores and third trophic level predators with the tobacco Nicotina tabacum bioreactor platform was initiated with the tobacco hornworm Manduca sexta (Lepidoptera: Sphingidae) and the spined soldier bug Podisus maculiventris Say (Hemiptera:Pentatomidae) to assess the non-target effects of the proteins, rFaeG, a pharmaceutical, and xylase, an enzyme, expressed in greenhouse and field-grown N. tabacum. The results indicate that rFaeG or xylase expressing tobacco did not significantly affect the hornworm mortality, relative growth rate and the nutritional indices for the tobacco grown under greenhouse or field conditions. The xylase tobacco-fed hornworms had lower mid-larval stage weights compared to those fed on the wild-type tobacco, and the survival was 25% less. However, by the pre-pupa and adult stage the difference in survival was no different for hornworm raised on all plant lines. Spined soldier bug nymph mortality was higher when they preyed upon hornworm larvae that in turn fed on wild-type tobacco leaves compared to those that consumed xylase-expressing tobacco leaves. However, the soldier bugs preying on hornworm consuming wild-type leaves had a positive growth rate, while those preying on the transgenic tobacco-fed hornworms either lost weight or did not gain weight on average over a 2 week period. In summary: 1) N. tabacum herbivores may adapt to different protein and nicotine concentrations during larval development and have similar growth and development to those feeding on wild-type plants; and 2) xylase-expressing N. tabacum had a negative impact of on third trophic level predators, but very high mortality of soldier bug nymphs was observed under all treatment conditions.