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Insect Pathology/ Biotechnology Lab

Insect Pathology/ Biotechnology Lab

We are interested in a variety of toxins that act either in the gut (e.g. Bt toxins) or within the hemocoel (e.g. neurotoxins) of the insect that have potential for use in insect pest management. 

Insect-specific neurotoxins

A wide variety of venomous species produce toxic peptides that are specific for insects. These pesticidal proteins represent an untapped resource for insect pest management due to the lack of an appropriate system for delivery from the insect gut to their target site within the body of the pest. We demonstrated that the coat proteins of plant viruses (luteoviruses) when fused to such peptides, effectively deliver them into the hemocoel of aphids, resulting in suppression of damaging aphid populations. We are now working to extend this approach to other pest insect systems.

Related publications

Transcytosis of Junonia coenia densovirus VP4 across the gut epithelium of Spodoptera frugiperda (Lepidoptera: Noctuidae). Kemmerer M, Bonning BC. Insect Sci. 2018 Apr 27. doi: 10.1111/1744-7917.12600

Bonning BC, Pal N, Liu S, Wang Z, Sivakumar S, Dixon PM, King GF, Miller WA. 2014. Toxin delivery by the coat protein of an aphid-vectored plant virus provides plant resistance to aphids. Nat. Biotechnol. 32(1):102-5. doi: 10.1038/nbt.2753.

Bonning BC, Chougule NP. 2014. Delivery of intrahemocoelic peptides for insect pest management.Trends Biotechnol. 2013 Dec 11. pii: S0167-7799(13)00177-7. doi: 10.1016/j.tibtech.2013.08.001.

Pal, N., Yamamoto, T., King, G.F., Waine, C., Bonning, B.C. 2013. Aphicidal efficacy of scorpion- and spider-derived neurotoxins. Toxicon 70:114-22.

Bt toxins

Insect specific toxins derived from the bacterium Bacillus thuringiensis (Bt) have been extensively used for insect pest management. Such toxins can be delivered by the bacterium itself (for use in organic agriculture or for suppression of mosquito larvae for example), and via transgenic plants. As Bt is a soil bacterium with toxins detected on plant surfaces, toxins have evolved that kill herbivorous insects that chew on plant material. There has been little selection for Bt toxins that kill sap-sucking or hemipteran insects that feed on plant sap. The hemipteran pests present a particular challenge as chemical insecticides represent the only tool available for management.

We are working on several approaches to improve the toxicity of Bt-derived toxins against Hemiptera.  Using the pea aphid as a model system, we examined the physiological bases for the lack of toxicity of selected toxins.  We demonstrated that different toxins behave differently in the aphid gut with some being unstable, and others binding but exerting only low levels of toxic action. Research on insect gut physiology to understand why toxins are or are not active when ingested led to a novel approach for retargeting of gut toxins to species that are not normally susceptible to a given toxin, such as the pea aphid (Chougule et al., 2013).

We are currently adapting this strategy to target insects that lack susceptibility to Bt toxins, or have developed resistance to Bt toxins including the soybean aphid, Aphis glycines, and the Asian citrus psyllid, Diaphorina citri.

Related publications

Toxicity of Bacillus thuringiensis-Derived Pesticidal Proteins Cry1Ab and Cry1Ba against Asian Citrus Psyllid, Diaphorina citri (Hemiptera). Fernandez-Luna MT, Kumar P, Hall DG, Mitchell AD, Blackburn MB, Bonning BC. Toxins (Basel). 2019 Mar 22;11(3). pii: E173. doi: 10.3390/toxins11030173.

Modification of Cry4Aa toward Improved Toxin Processing in the Gut of the Pea Aphid, Acyrthosiphon pisum. Rausch MA, Chougule NP, Deist BR, Bonning BC. PLoS One. 2016 May 12;11(5):e0155466. doi: 10.1371/journal.pone.0155466. eCollection 2016.

Bt toxin modification for enhanced efficacy. Deist BR, Rausch MA, Fernandez-Luna MT, Adang MJ, Bonning BC. Toxins (Basel). 2014 Oct 22;6(10):3005-27. doi: 10.3390/toxins6103005. Review.

Chougule, N.P., Li, H. Liu, S., Narva, K.E., Meade, T., Bonning, B.C. 2013. Retargeting of Bt toxins against hemipteran insect pests. Proc. Natl. Acad. Sci. USA

Chougule, N.P. and Bonning, B.C. 2012. Toxins for transgenic resistance to hemipteran pests. Special issue of the online journal Toxins “Insecticidal Toxins” 4(6), 405-429 doi:10.3390/toxins4060405

Li, H., Chougule, N.P., Bonning, B.C. 2011. Interaction of the Bacillus thuringiensis delta endotoxins Cry1Ac and Cry3Aa with the gut of the pea aphid, Acyrthosiphon pisum (Harris). J. Invertebr Pathology 107: 69-78.

Insect Gut Physiology

Electron microscope image of insect gut ciliaSimilar to the lack of efficacy of Bt toxins against aphids, improved understanding of the enzymatic environment encountered by toxin- or RNA-based control technologies can provide leads for improvement of- or delivery systems for- pest management agents. In this regard, stink bugs present a particular challenge.

Stink bugs are hemipteran pests that deleteriously impact 12 major agricultural crops across the globe. Stink bugs rely on a battery of digestive enzymes for extra-oral as well as gut-based digestion of plant tissues. Stink bug salivary enzymes are released into the plant and the partially digested proteins ingested for further degradation in the gut. With funding from CAMTech, we characterized both the proteases and nucleases in the gut and salivary gland of the southern green stink bug, Nezara viridula (Linnaeus) and the brown marmorated stink bug, Halyomorpha halys and enzyme coding sequences were identified. Biochemical characterization showed that the proteases in the gut and saliva differ radically in composition allowing for a two-pronged approach for digestion of plant material. Nuclease activity is abundant in the saliva of both stink bug species. These enzymes present a major challenge for the stability of putative stink bug control agents.

Related publications

Transcription and activity of digestive enzymes of Nezara viridula maintained on different plant diets. 2019. PE Cantón, BC Bonning. doi: 10.3389/fphys.2019.01553

The Principal Salivary Gland is the Primary Source of Digestive Enzymes in the Saliva of the Brown Marmorated Stink Bug, Halyomorpha halys. BC Bonning, S Liu. 2019. Frontiers in Physiology 10, 1255. doi: 10.3389/fphys.2019.01255

Proteases and nucleases across midgut tissues of Nezara viridula (Hemiptera: Pentatomidae) display distinct activity profiles that are conserved through life stages. 2019. PE Cantón, BC Bonning. Journal of insect physiology 119, 103965. doi: 10.1016/j.jinsphys.2019.103965.

Tissue-specific transcription of proteases and nucleases across the accessory salivary gland, principal salivary gland and gut of Nezara viridula. Liu S, Lomate PR, Bonning BC. Insect Biochem Mol Biol. 2018 Dec;103:36-45. doi: 10.1016/j.ibmb.2018.10.003. Epub 2018 Oct 21.

Proteases and nucleases involved in the biphasic digestion process of the brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae). Lomate PR, Bonning BC. Arch Insect Biochem Physiol. 2018 Jul;98(3):e21459. doi: 10.1002/arch.21459

Distinct properties of proteases and nucleases in the gut, salivary gland and saliva of southern green stink bug, Nezara viridula. Lomate PR, Bonning BC. Sci Rep. 2016 Jun 10;6:27587. doi: 10.1038/srep27587.