Bt Transgenic Lines Research Articles

Improved insect resistance against Spodoptera litura in transgenic sweetpotato by overexpressing Cry1Aa toxin.

Overexpressing the Cry1Aa gene in sweetpotato significantly reduced pest damage through disrupting the integrity of the midgut of Spodoptera litura larvae for resistance against target Lepidoptera insect pests in sweetpotato. Sweetpotato is susceptible to insect pests and diseases leading to yield losses during pest outbreaks. Lepidoptera insects such as S litura are especially important pests of sweetpotato. The effect of Cry1Aa gene on S. litura was investigated by overexpressing Cry1Aa gene in sweetpotato to relieve symptoms due to pest damage. When transgenic leaves were fed to the larvae of S. litura, the growth of the larvae was reduced, the larval quality decreased, and mortality was increased compared with the larvae that fed on wild-type leaves. Further anatomical analysis revealed that the columnar cells of the midgut epithelium of the BT group were significantly damaged, loosened, or disordered. Furthermore, the integrity of the midgut was destroyed. In addition, when potted seedlings of the wild-type and BT sweetpotato were inoculated with the same number of S. litura larvae, wild-type plants died on the eighth day after infestation, while BT transgenic lines still grew normally. This study showed that transgenic sweetpotato overexpressing Cry1Aa can prevent S. liturainfestation, and thus increase the yield of sweetpotato.

Whole-genome re-sequencing reveals molecular mechanisms of biomass changes in 11-year-old Bt transgenic poplar

Genome-wide insertions/deletions were identified in Bt transgenic poplar through whole-genome re-sequencing, revealing the molecular mechanisms underlying changes in the growth and wood characteristics of Bt transgenic poplar. Poplar is a fast-growing tree that relieves the wood demand in China. Previously, we found growth and wood characteristics differed in some lines of insect-resistant Bt transgenic poplar. Here, we selected five Bt transgenic lines (#12, #153, #172, #208 and #209), one untransformed control (CK2), one comparable control (CK3), and one native cultivar (JY, Populus × euramericana ‘Robusta’) in Xinjiang, China, for further study. Based on breast diameter, tree height, chemical content, and fibre morphology analyses, these transgenic lines showed fast growth and high-lignin and low-cellulose contents in the cell wall. In addition, genome-wide insertions/deletions (InDels) were compared between two transgenic lines (#12 and #153) and the untransformed control via whole-genome re-sequencing. GO enrichment and protein–protein interaction networks indicated the genes affected by differential InDels were related to programmed cell death and defence responses. This study provides new insight into the molecular mechanisms underlying changes in biomass characteristics in Bt transgenic poplar.

Grain yield and nitrogen use efficiency responses to N application in Bt (Cry1Ab/Ac) transgenic two-line hybrid rice

Transgenic crops with Bacillus thuringiensis (Bt) have been reported to be effective in controlling pests, and some Bt transgenic lines have been used to develop hybrid crop varieties including three-line and two-line hybrid rice (THR). However, it is unclear whether the insertion of an external Bt gene affects nitrogen uptake and N use efficiency (NUE) along with the grain yield of Bt-THR. Thus, field experiments were conducted in two adjacent fields located at Zhangbang village, Hubei province, China from May to October in 2011 and 2012. Treatments were arranged using a split-plot design with four replications. The main plots were N treatments with three rates (90, 135, 180kgha−1) in 2011 and four rates (0, 90, 135, 180kgha−1) in 2012. Four different tested varieties were grown in the subplots. The three Bt-THR examined were Guangliangyou-19 (GLY-19), Chuanyou-4198 (CY-4198), and Zheyou-3 (ZY-3), and the non-Bt control was Yangliangyou-6 (YLY-6) which was used as the check for the national variety traits in China at present. Pests (including Bt target pests, diseases and weeds) were strictly controlled to avoid yield loss. No significant differences were observed in the grain yield between GLY-19, ZY-3 and YLY-6 at each N application for both years. However, the grain yield in response to different N rates varied among different Bt-THR varieties and the control. CY-4198 showed a sensitive N response trait, which produced a maximum grain yield at 90kgNha−1, and further increases in N rates caused a yield decline. The other Bt-THR varieties demonstrated insensitive N responses similar to the control, where the maximum grain yield was at 135kgNha−1 and showed no significant yield decline when applied at 180kgNha−1 in both years. Among the three Bt-THR varieties, GYL-19 and ZY-3 demonstrated a similar N uptake ability, agronomic nitrogen use efficiency, N harvest index, N translocation efficiency, and recovery efficiency compared to the control, whereas those for CY-4198 was lower when the N application exceeded 90kgNha−1. In conclusion, some Bt-THR varieties (GLY-19 and ZY-3) demonstrated a comparable yield potential to the super hybrid control (YLY-6). Moreover, there was no evidence that insertion of the Bt gene changed N uptake and NUE-related traits, which indicated that the optimal N managements adapted by the THR varieties could also be introduced to Bt-THR. Thus, screening Bt-THR varieties might represent a feasible approach to synergistically improve grain yield and pest resistance without disrupting N nutrition.

Application of Ribosomal Intergenic Spacer Analysis to the Characterization of Microbial Communities in Rhizospheric Soils of the Bt Transgenic Chrysanthemum

In the present study, we examined the feasibility of using a simplified ribosomal intergenic spacer analysis (RISA) technique to investigate the impact of chrysanthemum genotypes, including Bt transgenic lines, the control parental line and a wild species, on microbial communities in their rhizospheric soils. Differential bands among the plant genotypes were identified from RISA profiles. Sequence data revealed that some bands showed high levels of similarity to known species, such as a fungal group of Exidiopsis and Exidia and a protozoan, Tetrahymena tropicalis. None, however, shared homology to either pathogenic or beneficial microbes that have previously been identified in association with both animals and plants.

Field and storage testing Bt potatoes for resistance to potato tuberworm (Lepidoptera: Gelichiidae).

Potato tuberworm, Phthorimaea operculella (Zeller), is the most serious insect pest of potatoes worldwide. The introduction of the Bacillus thuringiensis (Bt) toxin gene through genetic engineering offers host plant resistance for the management of potato tuberworm. We report on the field and storage studies to evaluate Bt-cry5 potato lines for resistance to potato tuberworm in Egypt under natural infestations and their agronomic performance in both Egypt and Michigan. From 1997 to 2001, field experiments were conducted at the International Potato Center (CIP) Research Station, Kafr El-Zyat, Egypt, and/or Agricultural Genetic Engineering Institute (AGERI), Giza, Egypt, to evaluate resistance to tuberworm. A total of 27 Bt-transgenic potato lines from six different Bt constructs were evaluated over a 5-yr period. After harvest and evaluation of the agronomic trials, storage evaluation of potato tuberworm damage was done at the CIP Research Station. The 1997 field trial was the first field test of genetically engineered crops in Egypt. Field tests to assess potato tuberworm resistance in Egypt were able to differentiate between the Bt-transgenic lines and the nontransgenic lines/cultivars in 1999, 2000, and 2001. The Bt-cry5-Spunta lines (Spunta-G2, Spunta-G3, and Spunta-6a3) were the most resistant lines in field with 99-100% of tubers free of damage. In the 2001 storage study, these lines were also over 90% free of tuberworm damage after 3 mo. NYL235-4.13, which combines glandular trichomes with the Bt-cry5/gus fusion construct, also had a high percentage of clean tubers in the field studies. In agronomic field trials in Michigan from 1997 to 2001, the Bt-transgenic lines in most instances performed similar to the nontransgenic line in the agronomic trials; however, in Egypt (1998-1999), the yields were less than one-half of those in Michigan. Expression of the Bt-cry5 gene in the potato tuber and foliage will provide the seed producer and grower a tool in which to reduce potato tuberworm damage to the tuber crop in the field and storage.

Insect Populations on Bacillus thuringiensis Transgenic Sweet Corn

Insect populations and damage in three plantings (early, mid-, and late-season) of Bacillus thuringiensis (Bt) transgenic sweet corn were compared to a non-transgenic isoline at Charleston, SC, during 2000. The transgenic corn was expressing the crylA(b) gene from B. thuringiensis var. kurstaki. No fall armyworms, Spodoptera frugiperda (J. E. Smith), were present in the early-planted crop, and numbers of corn earworms, Heliocoverpa zea (Boddie), were significantly reduced in the Bt-transgenic corn compared to the non-Bt isoline. The non-Bt isoline had 65% H. zea infested ears compared to only 10% ears from the Bt-transgenic line. Damage and numbers of H. zea and S. frugiperda also were significantly higher in the non-Bt sweet corn planted in mid- and late-season plantings. Percent damaged ears by H. zea was 77% in the non-transgenic sweet corn and 21% in the Bt-sweet corn during the mid-season crop. In the late-planted crop, populations of H. zea averaged 15 per 120 ears in the non-BT isoline compared to less than 2 per 120 ears in the Bt-transgenic crop. Whorl damage by fall armyworms significantly reduced plant height in both mid-season and late-season non-transgenic crops but not in Bt-transgenic sweet corn. Numbers of other insects and spiders were low and not significantly different between the two treatments. Bt transformed sweet corn will play a major role in reducing populations of H. zea, S. frugiperda and limiting pesticides in this crop.