Volatile Sex Pheromone Extraction and Chemoattraction Assay in <em>Caenorhabditis elegans</em>

Xuan Wan; Paul W. Sternberg

doi:10.3791/67115

JoVE Journal > Behavior

행동분석학

Volatile Sex Pheromone Extraction and Chemoattraction Assay in Caenorhabditis elegans

Published: August 09, 2024

doi:

10.3791/67115

Xuan Wan, Paul W. Sternberg

¹Division of Biology and Biological Engineering,California Institute of Technology

Summary

This protocol establishes methods for extracting and quantifying responses to the volatile sex pheromone in C. elegans, providing tools to study chemical communication and navigation trajectory.

Abstract

Chemical communication is vital in organismal health, reproduction, and overall well-being. Understanding the molecular pathways, neural processes, and computations governing these signals remains an active area of research. The nematode Caenorhabditis elegans provides a powerful model for studying these processes as it produces a volatile sex pheromone. This pheromone is synthesized by virgin females or sperm-depleted hermaphrodites and serves as an attractant for males.

This protocol describes a detailed method for isolating the volatile sex pheromone from several C. elegans strains (WT strain N2, daf-22, and fog-2) and C. remanei. We also provide a protocol for quantifying the male chemotaxis response to the volatile sex pheromone. Our analysis utilizes measurements such as chemotaxis index (C.I.), arrival time (A.T.), and a trajectory plot to compare male responses under various conditions accurately. This method allows for robust comparisons between males of different genetic backgrounds or developmental stages. Furthermore, the experimental setup outlined here is adaptable to investigating other chemoattraction chemicals.

Introduction

The interplay between chemical communication and reproductive success is a fundamental principle across the animal kingdom¹^,²^,³^,⁴^,⁵^,⁶^,⁷^,⁸^,⁹^,¹⁰. Sex pheromones trigger a wide array of sexually dimorphic behaviors essential for locating mates, coordinating the steps involved in finding and attracting a partner, and ultimately promoting the propagation of a species¹¹^,¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷. Significant progress has been made in understanding pheromone signaling, but the molecular mechanisms, neural circuits, and computational processes governing these interactions often remain incompletely defined¹⁸^,¹⁹^,²⁰^,²¹^,²²^,²³^,²⁴^,²⁵^,²⁶.

The nematode Caenorhabditis elegans provides a powerful model for dissecting these questions. Notably, C. elegans exhibits an unusual reproductive strategy-hermaphrodites can self-fertilize but also outcross with males²⁷^,²⁸^,²⁹^,³⁰^,³¹^,³²^,³³. This flexibility requires a robust communication system to signal reproductive status. C. elegans is known for its well-characterized water-soluble pheromones, the ascarosides, which play varied roles in development, behavior, and social interactions. Recent discoveries have unveiled a distinct class of volatile sex pheromones employed by nematodes. These pheromones are specifically produced by sexually mature C. elegans and C. remanei virgin females and sperm-depleted hermaphrodites, serving as an attractant for adult males²⁹^,³⁴^,³⁵. This attractant exhibits remarkable sexual dimorphism in its production and perception. The female somatic gonad governs the synthesis of this volatile sex pheromone, and production dynamically reflects reproductive status, ceasing upon mating and resuming several hours later²⁹^,³⁴.

Understanding nematode sex pheromone communication provides insights into the evolution of chemical communication systems, the interplay between reproductive state and behavior, and the mechanisms underlying sexually dimorphic neural processing²⁴^,²⁶^,³⁶^,³⁷^,³⁸^,³⁹. Studies implicate the amphid neuron AWA in males as critical for pheromone detection, with the G-protein-coupled receptor SRD-1 playing a key role in pheromone detection in males²⁴. C. elegans is well-suited for studying animal chemical communication, especially sex pheromone signaling, due to its reliance on the olfactory system for mate-searching. While much is known about ascaroside signaling, the volatile sex pheromone system offers unique opportunities for comparison²⁵^,²⁶^,³⁶^,⁴⁰^,⁴¹^,⁴²^,⁴³^,⁴⁴^,⁴⁵^,⁴⁶^,⁴⁷^,⁴⁸^,⁴⁹^,⁵⁰^,
⁵¹^,⁵²^,⁵³^,⁵⁴^,⁵⁵^,⁵⁶^,⁵⁷. Moreover, C. elegans is a powerful genetic model organism due to its fully sequenced genome, clearly defined cellular lineage, and well-characterized olfactory mutants.

However, the complete neural circuitry involved in processing this pheromone, the computations that translate its perception into targeted mate-searching behaviors, and its biosynthesis regulation remain to be fully elucidated. Further investigations into these processes are crucial for understanding the diverse mechanisms governing animal communication and reproductive behaviors. The identification of key genes involved in pheromone synthesis, secretion, and perception promises to unveil novel molecular players in animal communication. The assays described here provide a basis to address these questions.

Protocol

1. Crude sex pheromone extraction from females and hermaphrodites Protocol for C. elegans Synchronization Preparation of adult females or hermaphrodites Monitor culture plates daily until a large population of adult female/hermaphrodites exists and the OP50 food source depletes. Using fog-2 C. elegans and WT C. remanei females for crude sex pheromone extraction, prepare synchronized eggs from the mated females. NOTE: In this protoc…

Representative Results

Trajectory analysis of volatile sex pheromone perception defective strain in chemoattraction assay This chemoattraction assay reliably differentiates between wild-type and mutant strains of C. elegans in their response to volatile sex pheromones. Successful experiments with him-5 males consistently demonstrate robust chemotaxis towards the pheromone source. This is reflected in a high chemotaxis index (C.I.) (Figure 2), often exceeding 0.5, indicating…

Discussion

This protocol provides a robust methodology for the extraction of volatile sex pheromones from C. elegans, along with establishing a robust chemoattraction assay to measure male chemoattraction responses. Additional information can be found in the WormLab user guide (see the Table of Materials); for a basic code to visualize worm movement trajectory, see protocol section 7.3.8.5. Several crucial steps in the protocol are important for the outcome. First, careful synchronization of worm populatio…

Disclosures

The authors have nothing to disclose.

Acknowledgements

We are grateful to Dr. Tingtao Zhou for designing and writing the code for the trajectory visualizations used in our analysis. This work was supported by funding: R01 NS113119 (PWS), Chen senior postdoc fellowship, and the Tianqiao and Chrissy Chen Institute for Neuroscience.

Materials

10 cm Petri dishes	Falcon	25373-100	Falcon bacteriological Petri dish 100 x 15 mm
6 cm Petri dishes	Falcon	25373-085	Falcon bacteriological Petri dish 60 x 15 mm
C. remanei (EM464)	CGC
Centrifuge	Eppendorf	centrifuge 5418	Any brand should work.
Chemoattraction assay plates	Homemade solution	N/A	1.5% agar, 25 mM NaCl, 1.5 mM Tris-base, and 3.5 mM Tris-Cl
Cholesterol	Alfa Aesar	57-88-5
Dissecting Microscope	Leica	LeicaMZ75	Any brand should work.
E. Coli OP50	CGC
Ethanol	Koptec	64-17-5
fog-2(q71) (JK574)	CGC
him-5(e1490)(CB4088)	CGC
Household bleach	Clorox Germicidal bleach concentrated		Bleach
M9 buffer	Homemade solution	N/A	3 g KH₂PO₄, 11.3 g Na₂HPO₄.7H₂O, 5 g NaCl, H₂O to 1 L. Sterilize by autoclaving. Add 1 mL 1 M MgSO₄ after cool down to room temperature.
Magnesium Sulfate, Anhydrous, Powder	Macron	M1063-500GM-EA
Microwave	TOSHIBA	N/A	Any brand should work.
N₂	CGC
NaOH	Sigma-aldrich	S318-3	1 M
NGM plates solution	Homemade solution	N/A	2.5 g Peptone, 18 g agar, 3 g NaCl, H₂O to 1 L.Sterilize by autoclaving. Once the autoclave is done (2 h), wait until the temperature of the medium drops to 65 °C. Put on a hotplate at 65 °C and stir. Then add the following, waiting 5 min between each to avoid crystallization: 1 mL CaCl₂ (1 M), 1 mL MgSO₄ (1 M), 25 mL K₃PO4 (1 M, pH=6), 1 mL Cholesterol ( 5 mg/mL in ethanol).
Parafilm	Bemis	13-374-10	Bemis Parafilm M Laboratory Wrapping Film
Peptone	VWR	97063-324
Pipet- aid	Drummond Scientific	4-000-100	Any brand should work.
Plastic paper	Octago	Waterproof Screen Printing Inkjet Transparency Film	https://www.amazon.com/Octago-Waterproof-Transparency-Printing-Printers/dp/B08HJQWFGD
Potassium chloride	Sigma-aldrich	SLBP2366V
Potassium phosphate	Spectrum	7778-77-0
Pipette	Eppendorf	SKU: EPPR4331; MFG#: 2231300006	20 – 200 µL, 100 – 1000 µL, any brand should work.
Rotator	Labnet	SKU: LI-H5500	Labnet H5500 Mini LabRoller with Dual Direction Rotator. Any brand should work.
Sodium chloride	VWR	7647-14-5
sodium phosphate dibasic	Sigma-aldrich	SLCG3888
Tris-base	Sigma-aldrich	77-86-1
Tris-Cl	Roche	1185-53-1
Tryptone	VWR	97063-390
Vortex	Scientific industries	Vortex-Genie 2	Any brand should work.
WormLab system	MBF Bioscience	N/A	https://www.mbfbioscience.com/help/WormLab/Content/home.htm; https://www.mbfbioscience.com/products/wormlab/
Wormpicker	Homemade	N/A	made with platinum and glass pipet tips

References

Audesirk, T. E. Chemoreception in Alphysia californica. Iii. Evidence for pheromones influencing reproductive behavior. Behav Biol. 20 (2), 235-243 (1977).
Traynor, K. S., Le Conte, Y., Page, R. E. Queen and young larval pheromones impact nursing and reproductive physiology of honey bee (Apis mellifera) workers. Behav Ecol Sociobiol. 68 (12), 2059-2073 (2014).
Cowley, J. J., Wise, D. R. Pheromones, growth and behaviour. Ciba Found Study Group. 35, 144-170 (1970).
Epple, G. Pheromones in primate reproduction and social behavior. Adv Behav Biol. 11, 131-155 (1974).
Levinson, H. Z. Possibilities of using insectistatics and pheromones in pest control. Naturwissenschaften. 62 (6), 272-282 (1975).
Roelofs, W. Manipulating sex pheromones for insect suppression. Environ Lett. 8 (1), 41-59 (1975).
Marchlewska-Koj, A. Pheromones and mammalian reproduction. Oxf Rev Reprod Biol. 6, 266-302 (1984).
Keverne, E. B. Neuroendocrinology briefings 11: Pheromones and reproduction. J Neuroendocrinol. 12 (11), 1045-1046 (2000).
Rekwot, P. I., Ogwu, D., Oyedipe, E. O., Sekoni, V. O. The role of pheromones and biostimulation in animal reproduction. Anim Reprod Sci. 65 (3-4), 157-170 (2001).
Gomez-Diaz, C., Benton, R. The joy of sex pheromones. EMBO reports. 14 (10), 874-883 (2013).
Shorey, H. H., Gaston, L. K., Jefferson, R. N. Insect sex pheromones. Adv Pest Control Res. 8, 57-126 (1968).
Bruce, H. M. Pheromones and behavior in mice. Acta Neurol Psychiatr Belg. 69 (7), 529-538 (1969).
Shorey, H. H., Bartell, R. J. Role of a volatile female sex pheromone in stimulating male courtship behaviour in Drosophila melanogaster. Anim Behav. 18 (1), 159-164 (1970).
Bobadoye, B., et al. Evidence of aggregation-sex pheromone use by longhorned beetles (coleoptera: Cerambycidae) species native to Africa. Environ Entomol. 48 (1), 189-192 (2019).
Saunders, J. R. Sex pheromones in bacteria. Nature. 275 (5682), 692-694 (1978).
Schulz, S., Toft, S. Identification of a sex pheromone from a spider. Science. 260 (5114), 1635-1637 (1993).
Finnegan, D. E., Chambers, J. Identification of the sex pheromone of the guernsey carpet beetle, Anthrenussarnicus mroczkowski (coleoptera: Dermestidae). J Chem Ecol. 19 (5), 971-983 (1993).
Vaillancourt, L. J., Raudaskoski, M., Specht, C. A., Raper, C. A. Multiple genes encoding pheromones and a pheromone receptor define the b beta 1 mating-type specificity in Schizophyllum commune. 유전학. 146 (2), 541-551 (1997).
Ludewig, A. H., Schroeder, F. C. Ascaroside signaling in C. elegans. WormBook : the online review of C. elegans biology. , 1-22 (2013).
Sakai, N., et al. A sexually conditioned switch of chemosensory behavior in C. elegans. PLoS One. 8 (7), e68676 (2013).
Sengupta, S., Smith, D. P., Mucignat-Caretta, C. How Drosophila detect volatile pheromones: signaling, circuits, and behavior. Neurobiology of chemical communication. , (2014).
Zhang, Y. K., Reilly, D. K., Yu, J., Srinivasan, J., Schroeder, F. C. Photoaffinity probes for nematode pheromone receptor identification. Org Biomol Chem. 18 (1), 36-40 (2019).
Aprison, E. Z., Ruvinsky, I. Dynamic regulation of adult-specific functions of the nervous system by signaling from the reproductive system. Curr Biol. 29 (23), 4116-4123.e3 (2019).
Wan, X., et al. SRD-1 in AWA neurons is the receptor for female volatile sex pheromones in C. elegans males. EMBO Rep. 20 (3), e46288 (2019).
Peckol, E. L., Troemel, E. R., Bargmann, C. I. Sensory experience and sensory activity regulate chemosensory receptor gene expression in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 98 (20), 11032-11038 (2001).
Jang, H., et al. Neuromodulatory state and sex specify alternative behaviors through antagonistic synaptic pathways in. C. elegans. Neuron. 75 (4), 585-592 (2012).
Liu, K. S., Sternberg, P. W. Sensory regulation of male mating behavior in Caenorhabditis elegans. Neuron. 14 (1), 79-89 (1995).
Chasnov, J. R., Chow, K. L. Why are there males in the hermaphroditic species Caenorhabditis elegans. 유전학. 160 (3), 983-994 (2002).
Chasnov, J. R., So, W. K., Chan, C. M., Chow, K. L. The species, sex, and stage specificity of a Caenorhabditis sex pheromone. Proc Natl Acad Sci U S A. 104 (16), 6730-6735 (2007).
Susoy, V., et al. Natural sensory context drives diverse brain-wide activity during C. elegans mating. Cell. 184 (20), 5122-5137.e17 (2021).
Barriere, A., Felix, M. A. High local genetic diversity and low outcrossing rate in Caenorhabditis elegans natural populations. Curr Biol. 15 (13), 1176-1184 (2005).
Click, A., Savaliya, C. H., Kienle, S., Herrmann, M., Pires-Dasilva, A. Natural variation of outcrossing in the hermaphroditic nematode Pristionchus pacificus. BMC Evol Biol. 9, 75 (2009).
Anderson, J. L., Morran, L. T., Phillips, P. C. Outcrossing and the maintenance of males within C. elegans populations. J Hered. 101 (suppl_1), S62-S74 (2010).
Leighton, D. H., Choe, A., Wu, S. Y., Sternberg, P. W. Communication between oocytes and somatic cells regulates volatile pheromone production in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 111 (50), 17905-17910 (2014).
White, J. Q., et al. The sensory circuitry for sexual attraction in C. elegans males. Curr Biol. 17 (21), 1847-1857 (2007).
Fagan, K. A., et al. A single-neuron chemosensory switch determines the valence of a sexually dimorphic sensory behavior. Curr Biol. 28 (6), 902-914.e5 (2018).
Lipton, J., Kleemann, G., Ghosh, R., Lints, R., Emmons, S. W. Mate searching in Caenorhabditis elegans: A genetic model for sex drive in a simple invertebrate. J Neurosci. 24 (34), 7427-7434 (2004).
Frady, E. P., Palmer, C. R., Kristan, W. B. Sexual attraction: Sex-specific wiring of neural circuitry. Curr Biol. 22 (22), R953-R956 (2012).
Liu, Q., et al. Two preputial gland-secreted pheromones evoke sexually dimorphic neural pathways in the mouse vomeronasal system. Front Cell Neurosci. 13, 455 (2019).
Ludewig, A. H., et al. Pheromone sensing regulates Caenorhabditis elegans lifespan and stress resistance via the deacetylase sir-2.1. Proc Natl Acad Sci U S A. 110 (14), 5522-5527 (2013).
Golden, J. W., Riddle, D. L. A pheromone influences larval development in the nematode Caenorhabditis elegans. Science. 218 (4572), 578-580 (1982).
Butcher, R. A., Fujita, M., Schroeder, F. C., Clardy, J. Small-molecule pheromones that control dauer development in Caenorhabditis elegans. Nat Chem Biol. 3 (7), 420-422 (2007).
Jeong, P. Y., et al. Chemical structure and biological activity of the Caenorhabditis elegans dauer-inducing pheromone. Nature. 433 (7025), 541-545 (2005).
Butcher, R. A., Ragains, J. R., Kim, E., Clardy, J. A potent dauer pheromone component in Caenorhabditis elegans that acts synergistically with other components. Proc Natl Acad Sci U S A. 105 (38), 14288-14292 (2008).
Aprison, E. Z., Ruvinsky, I. Counteracting ascarosides act through distinct neurons to determine the sexual identity of C. elegans pheromones. Curr Biol. 27 (17), 2589-2599.e3 (2017).
Aprison, E. Z., Ruvinsky, I. Sex pheromones of C. elegans males prime the female reproductive system and ameliorate the effects of heat stress. PLoS Genet. 11 (12), e1005729 (2015).
Izrayelit, Y., et al. Targeted metabolomics reveals a male pheromone and sex-specific ascaroside biosynthesis in Caenorhabditis elegans. ACS Chem Biol. 7 (8), 1321-1325 (2012).
Kaplan, F., et al. Ascaroside expression in Caenorhabditis elegans is strongly dependent on diet and developmental stage. PLoS One. 6 (3), e17804 (2011).
Pungaliya, C., et al. A shortcut to identifying small molecule signals that regulate behavior and development in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 106 (19), 7708-7713 (2009).
Srinivasan, J., et al. A modular library of small molecule signals regulates social behaviors in Caenorhabditis elegans. PLoS Biol. 10 (1), e1001237 (2012).
Srinivasan, J., et al. A blend of small molecules regulates both mating and development in Caenorhabditis elegans. Nature. 454 (7208), 1115-1118 (2008).
Choe, A., et al. Ascaroside signaling is widely conserved among nematodes. Curr Biol. 22 (9), 772-780 (2012).
Von Reuss, S. H., et al. Comparative metabolomics reveals biogenesis of ascarosides, a modular library of small-molecule signals in C. elegans. J Am Chem Soc. 134 (3), 1817-1824 (2012).
Choe, A., et al. Sex-specific mating pheromones in the nematode panagrellus redivivus. Proc Natl Acad Sci U S A. 109 (51), 20949-20954 (2012).
Hsueh, Y. P., Mahanti, P., Schroeder, F. C., Sternberg, P. W. Nematode-trapping fungi eavesdrop on nematode pheromones. Curr Biol. 23 (1), 83-86 (2013).
Hong, M., et al. Early pheromone experience modifies a synaptic activity to influence adult pheromone responses of C. elegans. Curr Biol. 27 (20), 3168-3177.e3 (2017).
Ryu, L., et al. Feeding state regulates pheromone-mediated avoidance behavior via the insulin signaling pathway in Caenorhabditis elegans. EMBO J. 37 (15), e98402 (2018).
Diaz, S. A., Lindström, J., Haydon, D. T. Basic demography of Caenorhabditis remanei cultured under standard laboratory conditions. J Nematol. 40 (3), 167 (2008).
Bargmann, C. I. Chemosensation in C. elegans. WormBook : the online review of C.elegans biology. , 1-29 (2006).
Margie, O., Palmer, C., Chin-Sang, I. C. elegans chemotaxis assay. JoVE: J Vis Exp. (74), e50069 (2013).
Bargmann, C. I., Hartwieg, E., Horvitz, H. R. Odorant-selective genes and neurons mediate olfaction in C. elegans. Cell. 74 (3), 515-527 (1993).

This article has been published

Video Coming Soon

Keep me updated:

.

PDF

DOI

DOWNLOAD MATERIALS LIST

Cite This Article

Wan, X., Sternberg, P. W. Volatile Sex Pheromone Extraction and Chemoattraction Assay in Caenorhabditis elegans. J. Vis. Exp. (210), e67115, doi:10.3791/67115 (2024).