Abstract
Increased expression of the insect control protein genes of Bacillus thuringiensis in Populus has been critical to the development of genetically improved plants with agronomically acceptable levels of insect resistance. Bacillus thuringiensis (Cry1Ah1) proteins with highly specific toxicity against Hyphantria cunea were screened using an indoor bioactivity assay to obtain hyper-resistant transgenic poplars. Then, the Cry1Ah1 sequence was optimized and transformed according to the optimal codon in poplar using software of our own design (http://120.79.60.226:8080/u/chen/w/codonpoplar). A vector was constructed to transform poplar NL895. The Cry1Ah1 gene was transformed to poplar NL895 and six transgenic lines were obtained. The expression and insecticidal effect of the Cry1Ah1 gene in transgenic poplar were evaluated by PCR and ELISA, and the specific indoor activity and field insecticidal activity against H. cunea were compared with a control. We concluded that the insecticidal activity of the transgenic NL895 was significantly better against lower instar larvae of H. cunea than against higher instar larvae. The mortality and pupation rates clearly differed among the various instar larvae and between transgenic and non-transgenic poplar. We obtained poplar seedlings with hyper-resistance to H. cunea by screening Bt genes and optimizing their genetic sequence.
Highlights
Poplar is an important fast-growing forest tree
Of all the insect-resistance genes, Bacillus thuringiensis (Bt) has been the most widely studied in poplar (Peña and Séguin, 2001)
In 1993, China reported transgenic Populus nigra transformed with the Bt CrylAc gene; the mortality rate of gypsy moth increased to 80–90% (Tian et al, 1993)
Summary
Poplar is an important fast-growing forest tree. The total area planted with poplar in China is among the largest in the world (Hu et al, 2017; Wang et al, 2018), at about eight million hectares (Lu, 2008; Tun et al, 2018). In 2002, the State Forestry Administration approved a strain of transgenic poplar for commercialization in China; this was the world’s first commercialized transgenic tree species (Wang et al, 2018) During this period, insect-resistant transgenic P. nigra (Hu et al, 2001), P. deltoides (Ramachandran et al, 1993) P. euramericana (Wang et al, 1997), NL-80106 (Populus deltoides × Populus simonii) (Guo et al, 2004) and 741 poplar (Tian et al, 2000; Yang et al, 2003) were successfully cultivated, and there are resources for continuously introducing new insect-resistant poplar varieties (Zuo et al, 2018)
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