Jie Zhang

Bio: Jie Zhang is an academic researcher from Civil Aviation Authority of Singapore. The author has contributed to research in topics: Bacillus thuringiensis & Cry1Ac. The author has an hindex of 21, co-authored 70 publications receiving 1348 citations.

Cloning and characterization of a novel Cry1A toxin from Bacillus thuringiensis with high toxicity to the Asian corn borer and other lepidopteran insects

Abstract: A novel cry1A was cloned from Bacillus thuringiensis strain BT8 and expressed in the B. thuringiensis acrystalliferous mutant HD73-. The gene, designated cry1Ah1, encoded a protein with a molecular weight of 134 kDa. Reverse transcriptase-PCR and Western blotting showed that Cry1Ah was expressed in the host strain BT8. The toxin expressed in HD73- exhibited high toxicity against lepidopteran larvae of Ostrinia furnacalis, Helicoverpa armigera, Chilo suppressalis, and Plutella xylostella. The 50% lethal concentrations (LC50s) were 0.05, 1.48, 0.98 µg g-1 and 1.52 µg mL-1, respectively. The LC50s of Cry1Ah were significantly lower than that of Cry1Ac for H. armigera, C. suppressalis, and O. furnacalis, and lower than that of Cry1Ab and Cry1Ie for Ostrinia furnacalis. The high toxicity against a range of pest species makes this novel toxin a potential candidate for insect biocontrol.

Cross-resistance and interactions between Bt toxins Cry1Ac and Cry2Ab against the cotton bollworm

Abstract: To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. We conducted laboratory diet experiments with the cotton bollworm, Helicoverpa armigera, to evaluate cross-resistance and interactions between two toxins in pyramided Bt cotton (Cry1Ac and Cry2Ab). Selection with Cry1Ac for 125 generations produced 1000-fold resistance to Cry1Ac and 6.8-fold cross-resistance to Cry2Ab. Selection with Cry2Ab for 29 generations caused 5.6-fold resistance to Cry2Ab and 61-fold cross-resistance to Cry1Ac. Without exposure to Bt toxins, resistance to both toxins decreased. For each of the four resistant strains examined, 67 to 100% of the combinations of Cry1Ac and Cry2Ab tested yielded higher than expected mortality, reflecting synergism between these two toxins. Results showing minor cross-resistance to Cry2Ab caused by selection with Cry1Ac and synergism between these two toxins against resistant insects suggest that plants producing both toxins could prolong the efficacy of Bt cotton against this pest in China. Including toxins against which no cross-resistance occurs and integrating Bt cotton with other control tactics could also increase the sustainability of management strategies.

Bacillus thuringiensis: a century of research, development and commercial applications.

Abstract: Bacillus thuringiensis (Bt) is a soil bacterium that forms spores during the stationary phase of its growth cycle. The spores contain crystals, predominantly comprising one or more Cry and/or Cyt proteins (also known as δ-endotoxins) that have potent and specific insecticidal activity. Different strains of Bt produce different types of toxin, each of which affects a narrow taxonomic group of insects. Therefore, Bt toxins have been used as topical pesticides to protect crops, and more recently the proteins have been expressed in transgenic plants to confer inherent pest resistance. Bt transgenic crops have been overwhelmingly successful and beneficial, leading to higher yields and reducing the use of chemical pesticides and fossil fuels. However, their deployment has attracted some criticism particularly with regard to the potential evolution of pest-resistant insect strains. Here, we review recent progress in the development of Bt technology and the countermeasures that have been introduced to prevent the evolution of resistant insect populations.

Bacillus thuringiensis insecticidal three‐domain Cry toxins: mode of action, insect resistance and consequences for crop protection

Abstract: Bacillus thuringiensis bacteria are insect pathogens that produce different Cry and Cyt toxins to kill their hosts. Here we review the group of three-domain Cry (3d-Cry) toxins. Expression of these 3d-Cry toxins in transgenic crops has contributed to efficient control of insect pests and a reduction in the use of chemical insecticides. The mode of action of 3d-Cry toxins involves sequential interactions with several insect midgut proteins that facilitate the formation of an oligomeric structure and induce its insertion into the membrane, forming a pore that kills midgut cells. We review recent progress in our understanding of the mechanism of action of these Cry toxins and focus our attention on the different mechanisms of resistance that insects have evolved to counter their action, such as mutations in cadherin, APN and ABC transporter genes. Activity of Cry1AMod toxins, which are able to form toxin oligomers in the absence of receptors, against different resistant populations, including those affected in the ABC transporter and the role of dominant negative mutants as antitoxins, supports the hypothesis that toxin oligomerization is a limiting step in the Cry insecticidal activity. Knowledge of the action of 3d-Cry toxin and the resistance mechanisms to these toxins will set the basis for a rational design of novel toxins to overcome insect resistance, extending the useful lifespan of Cry toxins in insect control programs.

Whole Genome Phylogeny of Bacillus by Feature Frequency Profiles (FFP)

Abstract: Fifty complete Bacillus genome sequences and associated plasmids were compared using the “feature frequency profile” (FFP) method. The resulting whole-genome phylogeny supports the placement of three Bacillus species (B. thuringiensis, B. anthracis and B. cereus) as a single clade. The monophyletic status of B. anthracis was strongly supported by the analysis. FFP proved to be more effective in inferring the phylogeny of Bacillus than methods based on single gene sequences [16s rRNA gene, GryB (gyrase subunit B) and AroE (shikimate-5-dehydrogenase)] analyses. The findings of FFP analysis were verified using kSNP v2 (alignment-free sequence analysis method) and Harvest suite (core genome sequence alignment method).

FEMS microbiology letters

Abstract: All aspects of microbiology, including virology, are covered. Areas of special interest include: physiology, biochemistry and genetics (including molecular biology and 'omic' studies); biotechnology and synthetic biology; pathogenicity (including medical, veterinary and plant pathogens particularly those relating to food security); environmental microbiology (including ecophysiology, ecogenomics and meta-omic studies); virology; food microbiology (from food production and spoilage to food-borne pathogens); taxonomy and systematics (including publication of novel species and taxonomic reclassifications), and professional development (including education, training, CPD, research assessment frameworks, research metrics, best-practice and history of microbiology).