The first generation transgenic crops used strong constitutive promoters for transgene expression... more The first generation transgenic crops used strong constitutive promoters for transgene expression. However, tissue-specific expression is desirable for more precise targeting of transgenes. Moreover, piercing/sucking insects, which are generally resistant to insecticidal Bacillus thuringiensis (Bt) proteins, have emerged as a major pests since the introduction of transgenic crops expressing these toxins. Phloem-specific promoters isolated from Banana bunchy top virus (BBTV) were used for the expression of two insecticidal proteins, Hadronyche versuta (Blue Mountains funnel-web spider) neurotoxin (Hvt) and onion leaf lectin, in tobacco (Nicotiana tabacum). Here we demonstrate that transgenic plants expressing Hvt alone or in combination with onion leaf lectin are resistant to Phenacoccus solenopsis (cotton mealybug), Myzus persicae (green peach aphids) and Bemisia tabaci (silver leaf whitefly). The expression of both proteins under different phloem-specific promoters resulted in close to 100% mortality and provided more rapid protection than Hvt alone. Our results suggest the employment of the Hvt and onion leaf lectin transgenic constructs at the commercial level will reduce the use of chemical pesticides for control of hemipteran insect pests. Chemical pesticides have been used worldwide at a large scale for several decades to control insect pests 1. Many of these insecticides not only pollute the environment, but also affect other non-target insects and vertebrates, including humans 2. Additionally, chemical pesticides have a high potential to leach from the site of application to neighboring terrain or into underground water supplies 3. Plants depend on animals for 75% of their pollination 4 , and 80% of this pollination is carried out by insects, in particular bees 5. Agricultural insecticides show enormous direct and indirect impacts on non-target beneficial insects including changes in the biochemical pathways 6,7 , development 8,9 , adult longevity 10 and fecundity 11. Behavioral modifications have also been observed in beneficial insects. They tend to have navigation problems and cannot perform their functions in a proper manner when pesticides affect their nervous systems 11-13. It has also been reported that the feeding behavior of insects is changed by either the repellent action of pesticides, antifeedant properties, or inability to locate food due to reduced olfactory capacity after exposure to the pesticides 14-16. Although, only 2% of pesticides were found to affect vertebrates at agriculturally relevant concentrations, they nevertheless can have developmental, survival, genotoxic, cytotoxic, immunotoxic, and neurobehavioural effects 17,18. These effects can be direct (e.g. exposure during application) 19,20 or indirect (exposure through the consumption of food products exposed to the pesticides) 21-23. Given the profound environmental damage that can be caused by chemical pesticides, there is a clear need to develop new strategies, both to cope with highly resistant insect species and to avoid the secondary effects caused by agrochemicals. One approach is to produce transgenic crops expressing insecticidal toxins, such as genetically engineered potato, corn, and cotton expressing δ-endotoxins from the soil bacterium Bacillus thuringiensis (Bt toxins) 24. This bacterium, or its encoded Bt toxin, is the globally most commonly used biopesticide 25. Due to the extensive use of Bt genes in many crops, several insect species have developed resistance 26. Nevertheless, this technology has already exceeded the predicted time span that typically passes in the field before resistance emerges to
The first generation transgenic crops used strong constitutive promoters for transgene expression... more The first generation transgenic crops used strong constitutive promoters for transgene expression. However, tissue-specific expression is desirable for more precise targeting of transgenes. Moreover, piercing/sucking insects, which are generally resistant to insecticidal Bacillus thuringiensis (Bt) proteins, have emerged as a major pests since the introduction of transgenic crops expressing these toxins. Phloem-specific promoters isolated from Banana bunchy top virus (BBTV) were used for the expression of two insecticidal proteins, Hadronyche versuta (Blue Mountains funnel-web spider) neurotoxin (Hvt) and onion leaf lectin, in tobacco (Nicotiana tabacum). Here we demonstrate that transgenic plants expressing Hvt alone or in combination with onion leaf lectin are resistant to Phenacoccus solenopsis (cotton mealybug), Myzus persicae (green peach aphids) and Bemisia tabaci (silver leaf whitefly). The expression of both proteins under different phloem-specific promoters resulted in close to 100% mortality and provided more rapid protection than Hvt alone. Our results suggest the employment of the Hvt and onion leaf lectin transgenic constructs at the commercial level will reduce the use of chemical pesticides for control of hemipteran insect pests. Chemical pesticides have been used worldwide at a large scale for several decades to control insect pests 1. Many of these insecticides not only pollute the environment, but also affect other non-target insects and vertebrates, including humans 2. Additionally, chemical pesticides have a high potential to leach from the site of application to neighboring terrain or into underground water supplies 3. Plants depend on animals for 75% of their pollination 4 , and 80% of this pollination is carried out by insects, in particular bees 5. Agricultural insecticides show enormous direct and indirect impacts on non-target beneficial insects including changes in the biochemical pathways 6,7 , development 8,9 , adult longevity 10 and fecundity 11. Behavioral modifications have also been observed in beneficial insects. They tend to have navigation problems and cannot perform their functions in a proper manner when pesticides affect their nervous systems 11-13. It has also been reported that the feeding behavior of insects is changed by either the repellent action of pesticides, antifeedant properties, or inability to locate food due to reduced olfactory capacity after exposure to the pesticides 14-16. Although, only 2% of pesticides were found to affect vertebrates at agriculturally relevant concentrations, they nevertheless can have developmental, survival, genotoxic, cytotoxic, immunotoxic, and neurobehavioural effects 17,18. These effects can be direct (e.g. exposure during application) 19,20 or indirect (exposure through the consumption of food products exposed to the pesticides) 21-23. Given the profound environmental damage that can be caused by chemical pesticides, there is a clear need to develop new strategies, both to cope with highly resistant insect species and to avoid the secondary effects caused by agrochemicals. One approach is to produce transgenic crops expressing insecticidal toxins, such as genetically engineered potato, corn, and cotton expressing δ-endotoxins from the soil bacterium Bacillus thuringiensis (Bt toxins) 24. This bacterium, or its encoded Bt toxin, is the globally most commonly used biopesticide 25. Due to the extensive use of Bt genes in many crops, several insect species have developed resistance 26. Nevertheless, this technology has already exceeded the predicted time span that typically passes in the field before resistance emerges to
Uploads
Papers by zahid mukhtar