INSECTICIDAL TOXINS SECRETED BY BENEFICIAL NEMATODES AND THEIR POTENTIAL USE IN BIOLOGICAL CONTROL

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1015529
• Grant No.: 2018-67014-28067
• Cumulative Award Amt.: $150,000.00
• Proposal No.: 2017-08089
• Project Start Date: Mar 15, 2018
• Project End Date: Feb 20, 2020
• Grant Year: 2018
• Program Code: [A1112]- Pests and Beneficial Species in Agricultural Production Systems

Recipient Organization
UNIVERSITY OF CALIFORNIA, RIVERSIDE
(N/A)
RIVERSIDE,CA 92521

Performing Department
Nematology

Non Technical Summary
Food security is one of the most important global challenges of our age and insect pests continue to be a problem in agricultural systems, contributing to between 36%-42% losses in some staple crop systems. Reducing crop damage by pest insects is one strategy to increase food production and security. Toxins from the insect pathogen Bacillus thuringiensis (Bt) are widely used in biological control. Bt toxins, which are specifically toxic to insects and not mammals, are applied (sprayed) on crops and produced by transgenic crops to control insect pests in agriculture. However we are beginning to see resistance to these toxins in some populations of insect pests and there is growing concern that this resistance will increase and spread, making Bt toxins less effective. One way to combat resistance to Bt toxins is to use a variety of toxins with different modes of action, including the development of novel toxins. Recently we have discovered that insect-parasitic nematodes, which are considered "beneficial nematodes" since they kill insect pests, produce and release insecticidal proteins into their hosts. We propose to characterize these nematode-derived insecticidal proteins and to test the feasibility of using these toxins to control insect pests in agricultural systems. To do this we will separate the total mixture of ~500 proteins released by the nematodes into smaller fractions and testing these fractions for insecticidal activity. The results of this research could lead to the development of new natural compounds useful for killing insect pests.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
215	3130	1110	50%
215	3110	1120	50%

Knowledge Area
215 - Biological Control of Pests Affecting Plants;

Subject Of Investigation
3130 - Nematodes; 3110 - Insects;

Field Of Science
1120 - Nematology; 1110 - Parasitology;

Keywords

entomopathogenic nemeatodes

biological control

insect pests

toxins

Goals / Objectives
We propose to characterize novel insecticidal proteins from Steinernema carpocapsae, an insect-parasitic nematode that rapidly kills its hosts and has recently been shown to secrete insecticidal proteins into its hosts (Dillman et al., 2012; Lu et al., 2017). The only free-living stage of these nematodes, the infective juvenile (IJ), actively seeks out hosts and enters via natural openings (Fig. 1) (Dillman et al., 2012; Kaya and Gaugler, 1993). Once inside the host, the IJs transition from free-living to being actively parasitic, they release a complex mixture of proteins along with a bacterial symbiont associated with the nematodes into the host hemolymph. Together the nematode and bacteria kill the host and liquefy the tissue. After one or several rounds of reproduction, as resources become depleted, the rising generation of nematodes reassociates with the bacterial symbiont and develops into IJs, which emerge from the host cadaver in search or new insects to infect (Fig. 1). Steinernema carpocapsae is a well-known, extensively studied insect-parasite that belongs to a special group of parasites known as entomopathogenic nematodes (EPNs). It is a generalist parasite with an extremely broad host range, capable of infecting more than 250 different species of insects across 13 orders, in laboratory conditions (Hodson et al., 2011; Poinar, 1979). S. carpocapsae is a beneficial nematode that has been extensively used in integrated pest management programs globally (Lacey, 2006; Lacey and Georgis, 2012). However, the nematode-derived toxins have only recently been discovered, by our lab, and their identity and potential usefulness in biological control have yet to be explored (Lu et al., 2017).Our lab has long-term goals of better understanding host-parasite interactions, biological control, and the molecular factors involved in EPN killing of insect pests. Although EPNs are used globally in integrated pest management programs, it remains unclear why their efficacy in controlling pests in the field is inconsistent. We proposeto identify and characterize the insecticidal proteins released by S. carpocapsae and to determine the feasibility of using these insecticidal proteins in integrated pest management. We will accomplish these goals by pursuing the following two specific objectives:1. Characterize insecticidal proteins secreted by S. carpocapsae2. Determine feasibility of feeding nematode-derived toxins to kill insectsTo maximize the use of resources and accelerate the characterization of S. carpocapsae insecticidal proteins, we will perform the proposed research in Drosophila melanogaster and then in Manduca sexta. The fruit fly is a model system that has well established assays and will allow us to use minimal amounts of protein to identify active compounds. We will follow-up by performing the same experiments in M. sexta, which is a model insect pest that is larger than the fruit fly and will presumably require larger amounts of protein to observe activity.

Project Methods
To maximize the use of resources and accelerate the characterization of S. carpocapsae insecticidal proteins, we will perform the proposed research in Drosophila melanogaster and then in Manduca sexta. The fruit fly is a model system that has well established assays and will allow us to use minimal amounts of protein to identify active compounds. We will follow-up by performing the same experiments in M. sexta, which is a model insect pest that is larger than the fruit fly and will presumably require larger amounts of protein to observe activity.The specific objectives of our research are:1. Characterize insecticidal proteins secreted by S. carpocapsae2. Determine feasibility of feeding nematode-derived toxins to kill insectsMethods:1. Characterize insecticidal proteins secreted by S. carpocapsaeS. carpocapsae ESPs have been shown to have insecticidal activity in D. melanogaster, Bombyx mori, and Galleria mellonella. We hypothesize that there are one or a few proteins in the ~500 ESPs that have insecticidal activity and we will test this by fractionating the ESPs and testing those fractions of activity. Mass spectrometry will be used to identify the individual components of any active fractions and then individual proteins will be made recombinantly and tested for insecticidal activity.1A. Identification of candidate insecticidal proteins:For this objective we will collect ESPs from tens of millions of activatedS. carpocapsaeIJs for fractionation to narrow down the insecticidal candidates and ultimately pinpoint individual toxins. To eliminate possible contamination of the ESPs by toxins from symbiotic bacteria (Xenorhabdus nematophilais the symbiont ofS. carpocapsae), we will use axenic (bacteria-free) IJs for activation and ESP collection. We have established a method to obtain large numbers of axenic IJs by feeding nematodes with a mutant strain ofX. nematophilathat supports nematode growth but is defective in colonizing IJs. We have shown that ESPs from the activated axenicS. carpocapsaeis as toxic as the ESPs from symbiotic IJs (Lu et al., 2017). We will use ion exchange fractionation (GE HiTrap IEX Selection Kit) to separate the ESPs into 4-6 fractions and test the activity of the fractions by injecting them intoDrosophila melanogasteradults andManduca sextalarvae.D. melanogasteris small and a model insect whileM. sextais larger and a model pest. We will run SDS gels on active fractions to determine how many proteins are in the fraction and potentially perform mass spectrometry on the fractions. When we do perform mass spectrometry on the ESPs, we will use both the nematode proteome and the symbiotic bacterial proteome as library queries, so that bacterial contamination can be ruled out. Alternatively, further fractionation of active fractions using another fractionation technique (i.e. size or isoelectric point) may be needed to reduce the number of candidate insecticidal toxins. We would then test the secondary fractions for activity and perform mass spectrometry on active secondary fractions.We have performed a preliminary fractionation experiment ofS. carpocapsaeESPs using an anion exchange fractionation column (Fig. 4)(GE HiTrap IEX Selection Kit). The ESPs were separated into 3 fractions and each fraction was injected intoDrosophila melanogasteradults at a dose of 5 ng/fly. Only fraction #1 and #2 kill the flies as quickly as the full mixture of ESPs (Fig. 4). This indicates that it is feasible to separate toxic components from non-toxic ones. However, only the anion exchange column has been tested so far. We plan to test different columns in the GE HiTrap IEX Selection Kit, including a cation exchange column, to see if we get better resolution in our fractions. Once we have narrowed down to one or few toxic fractions using one type of column, we will further fractionate them using another type of column or another fractionation technique based on molecular size or isoelectric point. We will then find the toxic secondary fractions by injection intoD. melanogasteradults andM. sextalarvae, and analyze their protein contents by protein gel electrophoresis and mass spectrometry. If we can narrow down the candidates to fewer than 20 proteins, we will start analyzing the proteins individually.1B. Characterizing candidate insecticidal proteins:We will generate recombinant versions of candidate insecticidal proteins and test their activity by injection intoD. melanogasteradults andM. sextalarvae. We have produced a couple of recombinant proteins using Baculovirus andTrichoplusia ni(High-five® - Hi5) insect cells (Fig. 5)(Hamilton et al., 2016; Tonkin et al., 2011; Vulliez-Le Normand et al., 2012). Using an insect cell expression system eliminates contamination of endotoxins that can occur when using a bacterial expression system such asE. coli. However, it is possible that candidate insecticidal proteins we identify will be toxic to the insect cell expression system, in which case we are prepared to produce the recombinant proteins usingE. coli. We will test the activities of individual recombinant proteins by injection intoD. melanogasteradults andM. sextalarvae in a dose-response curve to determine the LD50. If we only find several weak toxins, we will mix them and test toxicity. With the toxicity tests, we expect to distinguish the possibilities that (1) a few individual proteins are potent toxins; (2) individual proteins are weak toxins but have combinatorial or synergistic effects. We will also want to know what cells or organs in the host are targeted by the toxin proteins we identify. We plan to make recombinant toxins with fluorescent (e.g., GFP) or luciferase tags to track the location of the recombinant proteins in the host after injection. We assume that hemocytes may be a good potential target, but we will dissect the injected hosts to find the specificity of the recombinant toxins. From there, we can start dissecting the molecular and cellular mechanisms of the functions of toxinsin vivo. Our published data indicated thatS. carpocapsaevenom/ESPs can anesthetize waxworms (Lu et al., 2017). Therefore, we expect that the ESPs might have some toxins targeting to the nervous system or muscles.2. Determine feasibility of feeding nematode-derived toxins to kill insectsWe will feed fractions of the nematode ESPs as well as individual recombinant proteins toD. melanogasteradults andM. sextalarvae in order to determine the feasibility of using the nematode-derived insecticidal toxins in pest control.2A. Feeding ESP fractions and individual proteins to insects:We will begin by feeding the whole collected ESPs toD. melanogasteradults andM. sextalarvae using established feeding assays. ForD. melanogaster, the CAFE assay is a quantitative feeding assay that allows researchers to determine the quantity of food being ingested by individual flies over a given period of time (Diegelmann et al., 2017). We will make use of this assay by providing flies with serial dilutions of toxins. We will make dilutions of the total ESPs, the ESP fractions, and individual recombinant proteins to test the activity of potential insecticidal proteins and their potency by oral ingestion. Similarly, forM. sextafeeding assays we will use filter papers moistened with different concentrations of total ESPs, the ESP fractions, and individual recombinant proteins using a described feeding assay (Gretes et al., 2016). The toxicity and dose of the different protein solutions will be tested and larval survival will be recorded. These experiments will allow us to determine the feasibility of using nematode-derived toxins to control pest insects and the data we acquire will serve as the foundation of our next grant proposal.

Progress 03/15/18 to 03/14/20

Outputs
Target Audience:Our target audience is other scientific researchers. We have disseminated our research progress with the scientific community through a peer-reviewed primary research article. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?I have been able to work with and train one postdoctoral fellow, one graduate student, and two undergraduates on this project. Further, it has allowed me to collaborate with colleagues and increase my understanding of biochemical tools such as mass spectrometry and some of the various applications and techniques that can be applied to understanding protein identity and function. How have the results been disseminated to communities of interest?We have disseminated our research progress with the scientific community through an open-accesspeer-reviewed primary research article. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We have made significant progress in characterizing the insecticidal proteins released by Steinernema carpocapsae. Thesecretome of S. carpocapsae, which includes all of the excreted/secreted proteins (ESPs) that are released upon activation ofthe infective juvenile stage was published in 2017, and reported to contain more than 470 protein (Lu et al., 2017).From that starting point, we have performed fractionation of this crude collection of ESPs using fast protein liquidchromatography (FPLC), using a strong anion exchange column. We collected fractions and tested them for activity byinjection into Drosophila melanogaster adults. We have demonstrated that only a small number of fractions collected in thisway maintain high toxicity to adult fruit flies. By performing mass spectrometry, we have identified 84 proteins in the toxicfraction, thus narrowing down from 472 nematode-derived proteins with possible insect activity down to 84 proteins. Wedetermined that 83 of these proteins are indeed nematode-derived, but that there was one protein in this active fraction thatwas bacterial in nature, coming from the bacterial symbiont Xenorhabdus nematophila, known to be associated with S.carpocapsae. We identified the contaminating protein as XaxB (D3VB23), a 39 kDa protein present at very low levels in theactive fraction. To rule out the possibility that the toxicity we were seeing was a result of bacterial contamination, we producedrecombinant XaxB protein using E. coli and have injected it at a dose of 200 ng/fly, resulting in zero toxicity. The crude ESPsare toxic at a dose of 20 ng/fly and the active fraction containing 84 proteins is toxic at a dose of 10 ng/fly, confirming that theXaxB protein is not the source of the toxicity and that the insecticidal activity we observe is a result of nematode-derivedprotein(s). This is an exciting result as it represents the first experimental finding of genuine insecticidal activity resulting from nematode-derived proteins and confirms the core hypothesis that is foundational to this grant.We are continuing to pursue further fractionation to reduce the number of candidate toxins from 83 proteins, but we have alsobegun producing and testing candidate proteins based on their abundance in the active fraction. Thus far we have cloned, produced, and purified a chymomtrypsin-like protein, a glycosyl hydrolase, and several sPLA2 proteins. We have started to produce a sapposin-like protein and an shTk-domain-containing protein. We began to test these proteins for toxicity by injecting quantified amounts of these proteins into adult fruit flies. So far we have not identified any proteins that by themselves are toxic to the flies when injects. However, we have found that nematode-derives sPLA2 enyzmes do modulate the immune system of adult flies such that they have increased susceptibility to bacterial infection. In addition to our progress investigating and characterizing the insecticidal proteins released by S. carpocapsae, we applied our strategy to another, distantly related entomopathogenic nematode, S. feltiae. This nematode is also ageneralist insect parasite but with a narrower host range than S. carpocapsae. We have activated S. feltiae IJs, collected theirESPs, identified their ESPs using mass spectrometry, and tested the crude ESPs for insecticidal activity in adult fruit flies. Wehave shown that, similar to S. carpocapsae, S. feltiae releases a variety of proteins, and this collection of proteins is alsohighly toxic to fruit flies and other insects. We identified 266 proteins that are released by S. feltiae, and this collection of 266proteins is highly toxic to insects. In comparing the ESPs of S. feltiae to those of S. carpocapsae, we found a subset of 52proteins that are present in the ESPs of both species. This may narrow down for us the candidate toxin proteins in S.carpocapsae, if we hypothesize that the mechanism for insecticidal activity is conserved between these two species. It is anexciting finding that insecticidal toxins are present in the ESPs of both species of nematodes, as it suggests that there may beseveral potential toxins that could be discovered and evaluated for their potential use in agriculture. The results of our work onS. feltiae have recently been accepted for publication in PLoS Pathogens. While we have not yet identified any proteins that are individually toxic, we have identified many candidates and continue to work towards testing these candidates.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Chang DZ, Serra L, Lu D, Mortazavi A, Dillman AR (2019) A core set of venom proteins is released by entomopathogenic nematodes in the genus Steinernema. PLoS Pathog 15(5): e1007626. https://doi.org/10.1371/journal.ppat.1007626

Progress 03/15/18 to 02/20/20

Outputs
Target Audience:Our target audience is other scientific researchers. We have disseminated our research progress with the scientific community through a peer-reviewed primary research article. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?I have been able to work with and train one postdoctoral fellow, one graduate student, and two undergraduates on this project. Further, it has allowed me to collaborate with colleagues and increase my understanding of biochemical tools such as mass spectrometry and some of the various applications and techniques that can be applied to understanding protein identity and function. How have the results been disseminated to communities of interest?We have disseminated our research progress with the scientific community through an open-accesspeer-reviewed primary research article. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We have made significant progress in characterizing the insecticidal proteins released by Steinernema carpocapsae. Thesecretome of S. carpocapsae, which includes all of the excreted/secreted proteins (ESPs) that are released upon activation ofthe infective juvenile stage was published in 2017, and reported to contain more than 470 protein (Lu et al., 2017).From that starting point, we have performed fractionation of this crude collection of ESPs using fast protein liquidchromatography (FPLC), using a strong anion exchange column. We collected fractions and tested them for activity byinjection into Drosophila melanogaster adults. We have demonstrated that only a small number of fractions collected in thisway maintain high toxicity to adult fruit flies. By performing mass spectrometry, we have identified 84 proteins in the toxicfraction, thus narrowing down from 472 nematode-derived proteins with possible insect activity down to 84 proteins. Wedetermined that 83 of these proteins are indeed nematode-derived, but that there was one protein in this active fraction thatwas bacterial in nature, coming from the bacterial symbiont Xenorhabdus nematophila, known to be associated with S.carpocapsae. We identified the contaminating protein as XaxB (D3VB23), a 39 kDa protein present at very low levels in theactive fraction. To rule out the possibility that the toxicity we were seeing was a result of bacterial contamination, we producedrecombinant XaxB protein using E. coli and have injected it at a dose of 200 ng/fly, resulting in zero toxicity. The crude ESPsare toxic at a dose of 20 ng/fly and the active fraction containing 84 proteins is toxic at a dose of 10 ng/fly, confirming that theXaxB protein is not the source of the toxicity and that the insecticidal activity we observe is a result of nematode-derivedprotein(s). This is an exciting result as it represents the first experimental finding of genuine insecticidal activity resulting from nematode-derived proteins and confirms the core hypothesis that is foundational to this grant.We are continuing to pursue further fractionation to reduce the number of candidate toxins from 83 proteins, but we have alsobegun producing and testing candidate proteins based on their abundance in the active fraction. Thus far we have cloned, produced, and purified a chymomtrypsin-like protein, a glycosyl hydrolase, and several sPLA2 proteins. We have started to produce a sapposin-like protein and an shTk-domain-containing protein. We began to test these proteins for toxicity by injecting quantified amounts of these proteins into adult fruit flies. So far we have not identified any proteins that by themselves are toxic to the flies when injects. However, we have found that nematode-derives sPLA2 enyzmes do modulate the immune system of adult flies such that they have increased susceptibility to bacterial infection. In addition to our progress investigating and characterizing the insecticidal proteins released by S. carpocapsae, we applied our strategy to another, distantly related entomopathogenic nematode, S. feltiae. This nematode is also ageneralist insect parasite but with a narrower host range than S. carpocapsae. We have activated S. feltiae IJs, collected theirESPs, identified their ESPs using mass spectrometry, and tested the crude ESPs for insecticidal activity in adult fruit flies. Wehave shown that, similar to S. carpocapsae, S. feltiae releases a variety of proteins, and this collection of proteins is alsohighly toxic to fruit flies and other insects. We identified 266 proteins that are released by S. feltiae, and this collection of 266proteins is highly toxic to insects. In comparing the ESPs of S. feltiae to those of S. carpocapsae, we found a subset of 52proteins that are present in the ESPs of both species. This may narrow down for us the candidate toxin proteins in S.carpocapsae, if we hypothesize that the mechanism for insecticidal activity is conserved between these two species. It is anexciting finding that insecticidal toxins are present in the ESPs of both species of nematodes, as it suggests that there may beseveral potential toxins that could be discovered and evaluated for their potential use in agriculture. The results of our work onS. feltiae have recently been accepted for publication in PLoS Pathogens. While we have not yet identified any proteins that are individually toxic, we have identified many candidates and continue to work towards testing these candidates.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Chang DZ, Serra L, Lu D, Mortazavi A, Dillman AR (2019) A core set of venom proteins is released by entomopathogenic nematodes in the genus Steinernema. PLoS Pathog 15(5): e1007626. https://doi.org/10.1371/journal.ppat.1007626

Progress 03/15/18 to 03/14/19

Outputs
Target Audience:We have disseminated our research progress with the scientific community through a peer-reviewed primary research article. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?I have been able to work with and train one postdoctoral fellow, one graduate student, and two undergraduates so far in working on this project. Further, it has allowed me to collaborate with colleagues and increase my understanding of biochemical tools such as mass spectrometry and some of the various applications and techniques that can be applied to understanding protein identity and function. How have the results been disseminated to communities of interest?We have disseminated our research progress with the scientific community through a peer-reviewed primary research article and plan to attend scientific conferences this coming year. What do you plan to do during the next reporting period to accomplish the goals?During this next reporting period we will continue our efforts in fractionation to narrow down the list of candidate toxin proteins. We will do this using FPLC, and combine two different types of fractionation such as anion exchange and size, using two different columns. This should increase the separation that we get and reduce our list of 83 candidate S. carpocapsae toxins. In addition to this fractionation, we will continue to choose rational candidates, express them transgenically, and test individual proteins from our list of candidates. We are currently in the process of testing 3 recombinant proteins and will test more during this next reporting period. We will also begin feeding assays using adult fruit flies and larval Manduca sexta. We will do these feeding assays with the active fractions to confirm that there is oral toxicity in the candidate toxins. We hope to be able to test individual candidate proteins in this feeding assay, but we will wait for confirmation of toxicity of the individual proteins in our injection assay before testing them in an oral assay.

Impacts
What was accomplished under these goals? We have made significant progress in characterizing the insecticidal proteins released by Steinernema carpocapsae. The secretome of S. carpocapsae, which includes all of the excreted/secreted proteins (ESPs) that are released upon activation of the infective juvenile stage was published in 2017, and reported to contain more than 470 protein (Lu et al., 2017). From that starting point, we have performed fractionation of this crude collection of ESPs using fast protein liquid chromatography (FPLC), using a strong anion exchange column. We collected fractions and tested them for activity by injection into Drosophila melanogaster adults. We have demonstrated that only a small number of fractions collected in this way maintain high toxicity to adult fruit flies. By performing mass spectrometry, we have identified 84 proteins in the toxic fraction, thus narrowing down from 472 nematode-derived proteins with possible insect activity down to 84 proteins. We determined that 83 of these proteins are indeed nematode-derived, but that there was one protein in this active fraction that was bacterial in nature, coming from the bacterial symbiont Xenorhabdus nematophila, known to be associated with S. carpocapsae. We identified the contaminating protein as XaxB (D3VB23), a 39 kDa protein present at very low levels in the active fraction. To rule out the possibility that the toxicity we were seeing was a result of bacterial contamination, we produced recombinant XaxB protein using E. coli and have injected it at a dose of 200 ng/fly, resulting in zero toxicity. The crude ESPs are toxic at a dose of 20 ng/fly and the active fraction containing 84 proteins is toxic at a dose of 10 ng/fly, confirming that the XaxB protein is not the source of the toxicity and that the insecticidal activity we observe is a result of nematode-derived protein(s). This is an exciting result as it represents the first experimental finding of genuine insecticidal activity resulting from nematode-derived proteins and confirms the core hypothesis that is foundational to this grant. We are continuing to pursue further fractionation to reduce the number of candidate toxins from 83 proteins, but we have also begun producing and testing candidate proteins based on their abundance in the active fraction. Thus far we have started to produce a sapposin-like protein, a chymomtrypsin-like protein, and an shTk-domain-containing protein. We are in the process of testing these individual candidate proteins for toxicity, all of which are highly abundant in the active ESP fraction. In addition to our progress investigating and characterizing the insecticidal proteins released by S. carpocapsae, we have begun to apply our strategy to another, distantly related entomopathogenic nematode, S. feltiae. This nematode is also a generalist insect parasite but with a narrower host range than S. carpocapsae. We have activated S. feltiae IJs, collected their ESPs, identified their ESPs using mass spectrometry, and tested the crude ESPs for insecticidal activity in adult fruit flies. We have shown that, similar to S. carpocapsae, S. feltiae releases a variety of proteins, and this collection of proteins is also highly toxic to fruit flies and other insects. We identified 266 proteins that are released by S. feltiae, and this collection of 266 proteins is highly toxic to insects. In comparing the ESPs of S. feltiae to those of S. carpocapsae, we found a subset of 52 proteins that are present in the ESPs of both species. This may narrow down for us the candidate toxin proteins in S. carpocapsae, if we hypothesize that the mechanism for insecticidal activity is conserved between these two species. It is an exciting finding that insecticidal toxins are present in the ESPs of both species of nematodes, as it suggests that there may be several potential toxins that could be discovered and evaluated for their potential use in agriculture. The results of our work on S. feltiae have recently been accepted for publication in PLoS Pathogens.

Publications

• Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: Chang D, Serra L, Lu D, Mortazavi A, Dillman AR (2019). A core set of venom proteins is released by entomopathogenic nematodes in the genus Steinernema. PLoS Pathogens.