The below list represents only planned manuscripts. Some of these
manuscripts have not been received by the Editorial Office yet. Papers
submitted to MDPI journals are subject to peer-review.
Type of Paper: Article
Title: Changes in Gene Expression in the Larval Gut of Ostrinia nubilalis in Response to Bacillus thuringiensis Cry1Ab Protoxin Ingestion
Authors: Jianxiu Yao 1,3, Lawrent L. Buschman 1,2, Chitvan Khajuria 1 and Kun Yan Zhu 1,*
Affliations: 1 Department of Entomology, 123 Waters Hall, Kansas State University, Manhattan, KS 66506, USA; E-Mail: email@example.com (K.Y.Z.)
2 Current Address: 963 Burland Dr., Bailey, CO 80421, USA
3 Current Address: Department of Entomology, 412 Minnie Belle Heep Building, Taxes A&M University, College Station, TX 77843, USA
Abstract: The European corn borer, Ostrinia nubilalis, is the target pest for transgenic corn expressing insecticidal toxins encoded by genes derived from Bacillus thuringiensis (Bt). We developed a cDNA microarray based on 15,000 cDNA elements representing 2,895 unique transcripts derived from the O. nubilalis larval gut. This microarray was used to monitor gene expression in early third-instar larvae of Bt-susceptible O. nubilalis after 6-hr feeding on diet with or without Cry1Ab protoxin. We identified 174 transcripts for which the expression was changed more than 2-fold in the gut of the larvae fed Cry1Ab protoxin (P ≤ 0.05). These transcripts represent 80 down-regulated and 94 up-regulated genes. Among these 174 differentially expressed transcripts, 106 showed BLAST results (e value < 1.0e-3), whereas 68 did not. Thirteen of these transcripts putatively encode proteins that are considered likely to be involved in Bt toxicity, and these transcripts include eight serine proteases, three aminopeptidases, one alkaline phosphatase, and one cadherin. The expressions of trypsin-like protease and three aminopeptidase transcripts were variable (three trypsin proteases and one aminpeptidase were up-regulated and one trypsin and two aminopeptidases was down-regulated), but some encoding three potential Bt-binding proteins, one aminopeptidase, alkaline phosphatase and cadherin, were consistently up-regulated in larvae fed Cry1Ab protoxin. The significantly up and down-regulated transcripts may be involved in Cry1Ab toxicity by activation, degradation, toxin binding and other related cellular responses. This study is the first large-scale survey of Cry1Ab protoxin induced transcriptional responses in O. nubilalis gut tissue and is expected to provide a platform for functional studies of toxin-insect interactions.
Keywords: Bacillus thuringiensis; European corn borer; Ostrinia nubilalis; Cry1Ab protoxin; microarray; transcriptional response
Type of Paper: Review
Title: Bacillus thuringiensis subsp. israelensis and its Dipteran-Specific Toxins
Author: Eitan Ben-Dov
Affiliation: Department of Life Sciences, Achva Academic College MP Shikmim, 79800, Israel; E-Mail: firstname.lastname@example.org
Abstract: Bacillus thuringiensis subsp. israelensis (Bti) is the first subspecies of B. thurengiensis that was found and used as an effective biological control agent against larvae of many mosquito and black fly species. The larvicidity of Bti resides in at least four major crystal pro-toxic proteins, of 134, 128, 72 and 27 kDa, encoded by cry4Aa, cry4Ba, cry11Aa and cyt1Aa respectively, and all mapped on the 128 kb plasmid known as pBtoxis. Despite the low toxicity of Cyt1Aa against exposed larvae, it is highly synergistic with the Cry toxins and their combinations and thus prevents selection of resistance in the targets. Low probability of developing resistance has been observed in field mosquito populations treated for decades with Bti-bioinsecticide.
Type of Paper: Review
Title: Bt Toxin Modification for Enhanced Efficacy.
Authors: M.T. Fernandez-Luna, B. Deist, M. Rausch and Bryony C. Bonning
Affiliation: Department of Entomology, Iowa State University, Ames, IA 50011; E-Mail: email@example.com (B.C.B.)
Abstract: Insect -specific toxins derived from Bacillus thuringiensis (Bt) provide a valuable resource for pest suppression. Here we review the different strategies that have been employed to enhance toxicity against specific target species or to modify the host range of Bt toxins. Toxin optimization provides a useful approach to extend their utility for suppression of pests that only exhibit low susceptibility to Bt toxins, and to overcome field resistance.
Type of Paper: Review
Title: Bacillus thuringiensis Toxins: An Overview of Their Known Biocide Activity
Authors: Leopoldo Palma, Delia Muñoz, Colin Berry and Primitivo Caballero
Affiliation: Instituto de Agrobiotecnología, CSIC-Gobierno de Navarra, 31192 Mutilva Baja, Navarra, Spain; E-Mail: firstname.lastname@example.org
Abstract: Bacillus thuringiensis (Bt) is a Gram positive, spore-forming bacterium that synthesizes parasporal crystalline inclusions containing one or more proteins (Cry and Cyt proteins) (Schnepf et al., 1998), some of which are toxic against a wide range of insects orders (Bravo et al., 2007; MacIntosh et al., 1990; Porcar et al., 2009), and nematodes (Wei et al., 2003). These toxins have been successfully developed as some of the most useful and environmental-friendly bioinsecticides in decades for herbivore insects with chewing mouthparts, such as caterpillars, beetles, and maggots, which ingest the toxins present on the plant surfaces along with their food. However, vast numbers of Bt isolates naturally present in the soil and the phylloplane synthesize Cry proteins whose biological activity is still unknown(Mizuki et al., 2000; Ohba et al., 2009). Bt also synthesizes insecticidal proteins during the vegetative growth phase, which are subsequently secreted into the growth medium. These proteins are commonly known as vegetative insecticidal proteins (Vips) and hold insecticidal activity against lepidopteran (Estruch et al., 1996), coleopteran (Warren et al., 1998) and some homopteran pests (Sattar and Maiti, 2011). A less characterized secretory protein with no amino acid similarity to previously known Vips, has shown insecticidal activity against coleopteran pests (Donovan et al., 2006) and termed as Sip protein (secreted insecticidal protein). Mtx-like and Bin-like proteins, which share amino acid similarities with mosquitocidal Mtx and Bin toxins, respectively, from Bacillus sphaericus, are also produced by some Bt strains (Berry, 2012; Peña et al., 2006). In summary, Bt insecticidal proteins may be classified into at least five distinct protein groups according to their amino acid identity and protein structure: Bin-like, three-domain Cry toxins, Cyt, Mtx-like, Sip, and Vip proteins (Peña et al., 2006). In addition to the aforementioned toxins, Bt produces some proteins, initially termed as non-insecticidal for their lack of toxicity against lepidopterans, dipterans and coleopterans, with outstanding toxicity against human cancer cells (Ohba et al., 2009), a human-pathogenic protozoan (Kondo et al., 2002) and the Oncomelania snail (Ali et al., 2010). In this review we provide an overview of the known active Bt toxins to date, which strongly suggests the pluripotential nature of the ample repertoire of toxins produced by this bacteria.