Towards better insect management strategy: restriction of insecticidal gene expression to biting sites in transgenic cotton

Abstract

Most of the commercialized Bt crops express cry genes under 35S promoter that induces strong gene expression in all plant parts. However, targeted foreign gene expression in plants is esteemed more important as public may be likely to accept 'less intrusive' expression of transgene. We developed plant expression constructs harboring cry1Ac gene under control of wound-inducible promoter (AoPR1) to confine Bt gene expression in insect wounding parts of the plants in comparison with cry1Ac gene under the control of 35S promoter. The constructs were used to transform four Turkish cotton cultivars (GSN-12, STN-468, Ozbek-100 and Ayhan-107) through Agrobacterium tumefaciens strains GV2260 containing binary vectors p35SAcBAR.101 and AoPR1AcBAR.101 harboring cry1Ac gene under control of 35S and AoPR1, respectively. Phosphinothricin (PPT) was used at concentration of 5 mg L-1 for selection of primary transformants. The primary transformants were analyzed for transgene presence and expression standard molecular techniques. The transformants exhibited appreciable mortality rates against larvae of Spodoptera exigua and S. littoralis. It was found that mechanical wounding of T 1 transgenic plants was effective in inducing expression of cry1Ac protein as accumulated levels of cry1Ac protein increased during post-wounding period. We conclude that use of woundinducible promoter to drive insecticidal gene(s) can be regarded as a valuable insect-resistant management strategy since the promoter activity is limited to insect biting sites of plant. There is no Bt toxin accumulation in unwounded plant organs, seed and crop residues, cotton products and by-products, thus minimizing food and environmental concerns.

Development of transgenic tobacco lines with pyramided insect resistant genes

“…In our study, only plants positive for introduced gene(s) were marked and subjected to further studies. Real-time quantitative PCR has emerged as a standard molecular technique to analyze relative expression of targeted genes (Maqbool et al, 2010;Rao et al, 2011;Anayol et al, 2016). In the present study, GUS and PCR positive transformants of Basma and Nail were subjected to qPCR and we observed that transgenic plants had increased expression of cry1Ac.…”

“…The expression level of cry1Ac protein varied among different transgenic plants of both cultivars ( Figure 6). The variability in cry1Ac expression in transgenic crops has previously been reported (Olsen at al., 2005;Puspito et al, 2015;Anayol et al, 2016) and has been attributed to the regulatory nature of 35S promoter (Sunilkumar et al, 2012). The cry toxin amount varied among transgenic plants in T0 and T1 generations (Figures 6 and 10).…”

An effective pest management approach in potato to combat insect pests and herbicide

“…35S CaMV is widely used promoter in commercialized transgenic crops as well as for other research purposes. Being constitutive in nature, 35S promoter induces expression of foreign gene all tissues types during plant growth and development (Mi et al 2015;Anayol et al 2016). In the present study, cry1Ac expression was also studied under the control of wound specific AoPRI promoter.…”

“…The construction of plant expression cassette has been described in Anayol et al (2016) in detail and represented as Fig. 1.…”

GENETIC APPROACHES FOR ENGINEERING BIOTIC STRESS RESISTANCE IN POTATO (Solanum tuberosum L.)

“…The use of tissue specific or light inducible promoter is being considered a more promising strategy in order to address public concerns on biosafety of transgenic crops (Anayol et al, 2016). The use of light inducible promoter restricted cry1Ab expression to aerial parts of transgenic potatoes and resulted in enhanced resistance against PTM.…”