EPN pheromones

Director: Fatma Kaplan, Ph.D.
Entomopathogenic nematode (EPN) pheromones

Dr. Kaplan has an experience to work on pheromones, nematodes as parasites (or vectors), or host as plants or insects, look at the chemical ecology of nematodes, understand how nematodes communicate using pheromones, explore the nematode pheromone knowledge for environmentally friendly control of plant parasitic nematodes, insect pests, and more…….

Project 1: Isolation of dispersal pheromone blend and infectivity signal to improve EPN dispersal and infectivity.

This is a very exciting project. This project has a CRADA with USDA (2015- 2016) and pending grants. Collaborators are Dr. David Shapiro (USDA-ARS, GA), Dr. Ed Lewis (UC-Davis, CA) and Paul Schliekelman (University of Georgia, GA).

Project 2:   Role of Xenorhabdus Bacteria on Pheromone Production by Steinernema Nematodes: Impact on Nematode Fitness and Formulation

This project is funded by a USDA-NIFA grant (2015 – 2018): Collaborators are Dr. Patricia Stock (Lead PI) at the University of Arizona and Dr. Rebecca Butcher (Co-PI) at the University of Florida.

Dr. Kaplan’s background in pheromones, nematodes and insects

In 2005, Dr. Kaplan accepted a postdoctoral position for chemistry training to identify pheromones from Caenorhabditis elegans for dauer development, aggregation and mating behavior at the Edison Laboratory at the National High Magnetic Field Laboratory where one of the world’s most sensitive NMR probes (1-mm high temperature superconducting) was developed. Dr. Edison had a collaborative grant with Dr. Sternberg at Caltech from the Human Frontier Science Program (HFSP) for identification of dauer, mate finding and aggregation pheromone from C. elegans. Since dauer pheromone was identified in 2005 after Dr. Kaplan accepted the position, she focused on isolation of mate finding pheromone from C. elegans. In 2007, two more compounds were reported with dauer pheromone activity from C. elegans (Butcher et al 2007, Nature Chem. Biol. 3:420-422). This was the year (2007), Dr. Kaplan purified a component of mating pheromone. We realized that the same class of compounds regulated both mate finding behavior and development (dauer/dispersal larvae formation). Dr. Kaplan’s postdoc advisor Dr. Art Edison asked Dr. Schroeder to chemically synthesize the compound we purified. Since these pheromones were a class of compounds, regulated both development and behavior and the compound Dr. Kaplan purified was the fourth compound to be identified. Therefore, it was named ascaroside number 4 (ascr#4).  This work was published in Nature in 2008 (Srinivasan and Kaplan et al. 2008, Nature 454: 1115–1118 and Kaplan et al. 2008, Mag Lab Reports 15: 14-15). The same year, using Dr. Kaplan’s data on pheromones (Kaplan et al. 2009 J. Chem. Ecol.; Kaplan et al. 2011 PLoS ONE), Dr. Kaplan participated in writing Dr. Edison’s collaborative NIH grant (funded in 2009), “Comparative Behavioral Metabolomics in Nematodes”, with the main objective of “identification of Panagrellus redivivus mating pheromone and pheromone receptors”. This very rare training opportunity on writing collaborative NIH RO1 grant.

In Aug 2008, Dr. Kaplan accepted a position at the Center for Medical, Agricultural and Veterinary Entomology (CMAVE) at USDA-ARS with the goal of expanding C. elegans pheromones to plant parasitic nematode, root knot nematodes (RKNs, Meloidogyne spp.).  Application of pheromone knowledge from C. elegans to RKN was a big leap so Dr. Kaplan started with insect pathogenic nematodes (EPNs) which are closely related to C. elegans, to test whether this idea was feasible. She picked an agronomically important behavior (dispersal behavior of dauer/dispersal larvae) which was also aligned well with the CMAVE, USDA-ARS chemistry unit’s expertise in chemical ecology and pheromones. First, she developed a fast visual bioassay using EPN dispersal larvae, and then she adapted this assay to C. elegans. After that, Dr. Kaplan identified dispersal blend from C. elegans by using comparative metabolomics (LC-MS based ascaroside profiling). The ascr#2, ascr#3, ascr#8 and icas#9 together gave dispersal activity in C. elegans. Furthermore, the C. elegans blend was recognized by EPN dispersal larvae and RKN dispersal larvae. This suggested that may be EPNs and RKNs use ascaroside pheromones for their dispersal. Dr. Kaplan started purifying EPN (S. feltiae) dispersal cue from insect host cadavers. She found that S. feltiae dispersal was regulated by a blend of  compounds and one component was an ascaroside (ascr#9). Dr. Kaplan published this work in 2012 (Kaplan et al. 2012, PLoS ONE 7 (6), e38735). This was very well received by the EPN community. Dr. Kaplan met wonderful scientists, established collaborations and wrote research grants.

At CMAVE, Dr. Kaplan gained additional experience on insect development and physiology and insects as vectors through collaborative research. Insects as vectors of diseases and interaction with environment. This project is about how an invasive weed affects vector (insect) fitness for malaria transmission. Dr. Kaplan led the NMR based structural verification a toxic compound, parthenin from invasive weeds (PLoS ONE (2015). Insect development and physiology.  This project was about isolating insect hormone which affects insect development. Dr. Kaplan led the NMR based structural elucidation of insect hormone which was isolated from insect blood. I also verified the structure with synthetic methyl farnesoate (J. Nat. Prod. (2014) 77:402-405). In an insect communication project, Dr. Kaplan led and elucidated the citrus Diaprepes root weevil mating pheromone that had eluded structure determination efforts for over ten years. It was published in J. Chem. Ecol. (2012) 38: 408–417 and highlighted by MagLab Science Highlights, and patented (US Patent No: US 8,663,621).

In 2011,  Dr. Kaplan was awarded the Schroth Faces of the Future, Nematology, a prestigious award by the American Phytopathological Society. She followed that up with a 5 year vision essay for nematode pheromones in December 2013 that was selected for publication in the Genetics Society of America newsletter (The GSA Reporter 2014, Winter issue).