This document discusses how organisms interact in their environment through communication. It focuses on nematodes and their use of chemical signals called semiochemicals. Nematodes have developed a sophisticated chemical language to organize their communities using pheromones, allomones, synomones and kairomones. The document examines nematode nervous systems, chemosensory organs, the role of age and other factors on attractants, and examples of nematode communication such as attraction to hosts, fungi, and responses to sex pheromones. It discusses recent research findings on quorum sensing and chemical mating cues in C. elegans.

1. NEM 893 - DOCTORAL SEMINAR - III (0+1)
BY
C. MATHIVATHANI
2016801402
1

2. How organisms interact
in an environment?
2

3. Content
 Introduction
 Communication
 Semiochemicals
 Nervous system
 Quorum sensing
 Research findings
 Conclusion.
3

4. • Exchange of information between individuals.
• Most nematode language is innate.
• Nematodes developed a sophisticated chemical
language - use to organize their communities.
• Exploring the nervous system senses and
deciphering the different chemical messages.
Introduction
4

5.  Nematode messages
are more complex -
combining two or
more different
molecules.
5

6.  Recognition of inmates.
 Locating or identifying the opposite sex.
 Facilitation of courtship and mating.
 Locating food.
 Regulating spatial distribution of
individuals (aggregation or dispersal).
 Warning of danger.
 Expressing threat or submission.
Why Nematodes Communicate ?
6

7. OLFACTORY
AUDITORY
CHEMICAL
STIMULI
Communication
7

8. • Chemicals that mediate inter and intra specific
interactions between organisms.
Semiochemicals
Pheromones Allelochemicals
Huettel, 1986
Semiochemicals
8

9. (Huettel, 1986)
9

10. • Nematodes - ability to chemo-orientate using a
combination of head to tail chemosensory sensors
to simultaneously compare the intensities of the
stimulus across their body length.
(Hilliard, 2002)
10

11. Sense organs
11

12. • The nervous system
is the conduit
between stimulus,
reception and
behavioural output.
Nervous System
12

13. Functional unit - Neuron
Neurocyte
Nerve fibre (Axon)
Dendrites
Process
13

14. Chemicals that cause a physiological or
behavioural response between members of same
species. Produce intraspecific signals.
• Sex – Attraction & Aggregation
• Epidietic – Dauer inducing
• Alarm - Protection
The discovery of Bombykol prompted Karlson and Luscherin
1959 to introduce the term “pheromone”
Pheromones
14

15. • Pheromone communication between nematodes -
first observed in Panagrolaimus rigidus (Greet,
1964), Globodera & Heterodera (Green and Plumb,
1970).
• Aggregating pheromones - Nippostrongylus
brasiliensis, and the active fraction has been
isolated and partially identified.
• All possible combinations of sex attraction were
observed in bioassay no aggregating pheromones
were detected in Radopholus sp. (Greet, 1975).
15

16. • Reproductive organs.
• Only female nematodes secrete pheromones.
Site of Secretion
16

17. • Nematodes emit the pheromone in aqueous or semi
aqueous medium.
 Q - pheromone emission rate (molecules/second)
 K - Behavioral threshold concentration
(molecules/cm3)
• For effective function of pheromone Q/K ratio
should be more.
The function of the pheromone diffusion
is determined by Q/K. ratio
Pheromone diffusion and flow
17

18. Initiation
Establishment of concentration gradient
Continuous emission of pheromone
Gradient – stable
Attraction
(Samoiloff et al., 1973)
Steps in Pheromone Secretion
18

19. • Generally - No storage organ to store pheromone.
• H. schachtii & G. rostochiensis - dead female
attracts nematode.
• Pheromones are released by apertures.
PRODUCTION
RELEASE
STORAGE
(Green, 1980)
Mechanism of Secretion
19

20. SPECIES AUTHOR
Anchylostoma caninum Roche, 1966
Nippostrongylus brasiliensis Gimmenze and Roche, 1972
Panagrellus rigidus Greet, 1964
Panagrellus silusiae Duggal, 1978
Rhabditis pellio Somers et al., 1977
Trichenella spiralis Bone et al., 1977
Trichenella spiralis Bonner and Etges, 1967
Ditylenchus dipsaci Windrich, 1973
Globodera pallida Green and Plumb, 1970
Sex PheromonesSex pheromones
20

21. • A receptor must be present to accept the signal.
• Nematode transforms the signal to a behavioral
response.
• Chemoreceptors - anterior region.
Chemo-orientation is vital for nematode survival &
essential for detection of host plant exudates, food
stimulants and sex pheromones.
Pheromone - Reception
21

22.  Amphids
 Phasmids
 Labial sensilla
 Spicules
Nematode signalling components present in the
chemosensory organs are in contact with external
environment - exposed to antagonistic molecules that
could block their interaction with host cues.
(Perry, 2005)
Mechanism of attraction
22

23. Head region of nematode
23

24. Tail region of nematode
24

25. Spicule of nematode
25

26. Chemofactor exuded by chemosensory sensillae bind to the cuticle
glycocalyx
As concentration increases in the zone around the nematode head.
Competitive displacement of previously bound molecules allow diffusion
along the cuticle surface (the glycocalyx).
Penetration of molecules into the pores of the sensillae.
Eventual detection by receptors on sensilla membranes .
Pheromone - Reception
26

27. Initiating the events leading to chemotaxis
Head waving behavior of the nematode
Enhances the opportunity for binding chemoattractants
to the cuticle area surrounding the cephalic sensillae.
27

28. 28

29. • Amphids - number of dendritic processes
surrounded by secretions produced by the
glandular sheath cell.
Amphids
29

30. Structure of cilia
30

31. (Dwyer et al., 2001).
31

32. 32

33. Ultrastructure of Sensilla
33

34. • Nematodes - possess well-developed sensilla to
sense physical and chemical cues (Olfaction).
(Coomans and De Grisse, 1981).
• Olfaction - for chemical sensing of C. elegans
possess gustatory sense organs.
(Bargmann et al., 1993).
Responses to Signals
34

35. Example
• Males & second stage juveniles (J2s) of
Heterodera schachtii - oriented behavior -
presence of female sex pheromone or host root
diffusates.
• Individuals random movement - absence of
stimuli - exploration area, increased track lengths
and reduced number of forward & backward
movements.
(Clemens et al., 1994)
35

36. 36

37. Short-distance
pheromone
Guide male
orientation towards
the female (taxis).
Long-distance
pheromone
Enhance the
movement of males
(kinesis).
(Dusenbery, 1980)
In C. elegans, Male nematode responses to
female sex pheromones.
Taxes and Kineses
37

38.  Temperature - 25-30oC
 pH - Neutral
 Medium - varies according to the habitat
 Population - Generally no effect
 Age - decreases with increasing age
Factors affecting attractants
38
(Curtis, 2007)

39. S.
No
Nematode Stage Reference
1. Globodera sp.
Heterodera schachtii
Virgin female Green et al., 1970
2. Panagrellus silusiae Pre – adult Cheng, 1971
3. Rhabditis pellio Matured adult Somers et al., 1977
4. Panagrellus ridivivus After final
moult
Duggal, 1978
Age factor
39

40. • Ions : e.g. Ca2+ , Na+, K+, Mg2+.
• The most powerful attractants - cyclic
nucleotides, cAMP and cGMP.
Classes of attracting chemicals
(Perry, 1983)
40

41. • A substance with sex pheromone activity from
females of H. glycines - vanillic acid used in
preliminary field trials to disrupt mating of this
species.
• Vanillic acid did not attract males of H. schachtii or
G. rostochiensis.
• It reveals that H. schachtii posses two different
types of sex pheromones - pentane and methanol.
Greet et al. (1978)
(Perry & Beane, 1983).
41

42. • Mate attraction is dictated by specific glycosides
and side chains of the dideoxysugar ascarylose, a
class of molecules – Ascarosides (Daumone).
• Modifications of ascarosides dictate different
behaviors (Male attraction, hermaphrodite attraction
& dauer formation).
• The existence of a complex, synergistic, chemical
mating cue system between males and
hermaphrodites in C. elegans.
Chemical Mating Cues in C. elegans
42

43. 43

44. Stage of the female. Size of the population
Pheromone secreted
by other nematodes.
Pheromone diffusion
track
Carbondioxide
Modification of the responses
44

45. • Attraction of nematodes to nematophagous
fungus- the animals are lured into the vicinity of
their natural enemies, then captured and digested
by the fungi.
Attraction to Nematophagous
Fungi
45

46. • The nematode-trapping fungi utilize hyphal traps
to capture nematodes.
• Traps – “NEMIN” spontaneously produced or
induced by nematodes or proteinaceous
compounds, e.g. peptides.
46

47. • Nematodes - attracted to both living roots & root exudates.
• Plant and carbon dioxide - principal attractant.
• In other nematodes, e. g. the Golden cyst nematode
Globodera rostochiensis, - highly host-specific, very specific
chemoattractants.
Nematode towards Root
exudates
47

48. • In G. rostochiensis J2 changes in amphidial
structure during hatching process.
• The absence of secretions and the shrunken state of
the sheath cell in unhatched nematodes - amphids
may not be functional before hatching.
48
(Perry & Beane, 1983).

49. • Nematodes with lowest lipid content attracted
to the pine wood volatile α-myrcene.
• Highest lipid content attracted to toluene
hydrocarbon in the cuticle of the beetle vector
for the nematode.
(Stamps & Linit, 2001).
49

50. • Nematode quorum sensing (QS) signals
regulate entry into a hardened larval stage.
• Affects host parasite interaction provides
platform to develop drugs that combat human
parasitic nematodes, breed nematode resistant
plants & to control insect pests.
Quorum sensing (QS)
50
(Reynolds et al., 2010).

51. • Nematicidal compounds produced by many
different species of plants - resistance to
root-knot nematodes in marigolds,
Tagetes sp. – Terthinyl compounds was
first reported in 1938.
Allomones
51

52. • Treatment of adult female P. penetrans with
aldicarb - hypertrophy of the internal dendrite
terminals within the amphidial sheath cell.
52

53. • Nordlund and Lewis proposed the term
"synomone" for chemical that mediate
mutualistic interactions.
• Chemicals benefit both the receiver and the
emitter, with the behavioral or physiological
response being adaptively favorable.
Synomones
53

54. • In nematode - Host-parasite recognition mediated
by lectin-carbohydrate interactions.
• Some lectins also bound to the external cuticular
surface.
• Species and race specific binding patterns were
observed for both amphidial and cuticular binding
sites.
Kairomones
54

55. • Lectin binding sites on the surface of
Meloidogyne incognita Races 1, 2, 3, and 4;
M. javanica; M. arenaria Races 1 and 2; and
M. hapla .
(Michael, 1988)
55

56. Extracellular recordings of electrical activity inside the body of
male G. rostochiensis in response to stimulants such
as the sex pheromone from adult female G. rostochiensis.
Electrophysiological analyses
of nematode responses
56

57. Research findings57

58. Root exudates include secretion of ions, free
oxygen and water, enzymes, mucilage and a
diverse array of primary and secondary
metabolites.
(Bertin et al., 2003).
58

59. 59

60. • Root exudates not only contain compounds that
induce nematode hatching, attraction and
repellence to roots but also compounds that induce
characteristic nematode exploratory behaviour,
including stylet thrusting; release of secretions in
preparation for root penetration; aggregation and
increase in nematode mobility.
(Curtis, 2007).
60

61. Solanoeclepin A
The hatching stimulus for the parasitic
potato cyst nematode
(Curtis, 2007).
61

62. • In vitro, plant signals present in root exudates,
trigger a rapid alteration of the surface cuticle
of M. incognita and the same changes were also
induced by indole-acetic acid (IAA).
• IAA binds to the chemosensory organs of
M. incognita
• IAA acts as a signal that orientates the
nematode on the root surface in the
rhizosphere and/or inside the root tissue and
thereby promotes nematode infection. 62

63. • The behavioral response of adult male S. carpocapsae
to several different potential sources were measured.
• Species-specific communication takes place between
adult entomopathogenic nematodes within the host
cadaver just prior to mating.
63

64. Male S. carpocapsae responded to
virgin females only.
64

65. Ethogram on events till copulation
65

66. • Compare the olfactory responses of Heterorhabditis
and Steinernema infective juveniles (IJs) to those of
Caenorhabditis elegans dauers.
• Ability to respond universally produced signal
carbon dioxide (CO2), using gas chromatography-
mass spectroscopy. 66

67. • The parasitic IJs and C. elegans dauers that lack BAG neurons are not
attracted to CO2 .
• In addition, S. carpocapsae IJs that lack BAG neurons do not exhibit CO2-
induced jumping .
• BAG neurons are required for CO2 attraction in both free-living and parasitic
nematodes and contribute to both chemotaxis and jumping. 67

68. 68

69. Modified Y chamber
69

70. • Two provisos:
(i) All of the channels through which the attractant diffuses
are accessible to the nematodes.
(ii) Nematodes can resolve all chemical gradients no matter
how small.
The predictions are supported by experimental studies of the
movement patterns of the root-knot nematodes
Meloidogyne incognita and Meloidogyne graminicola in
Modified Y-chamber olfactometers filled with Pluronic gel.
70

71. 71

72. • Movement of three species of insect-parasitic
nematodes, Steinernema carpocapsae, Steinernema
feltiae & Heterorhabditis megidis in response to
chemical and vibrational cues.
• All species showed strong, significant taxes towards
the vibrations.
• In soils, the utility of chemical cues as attractants is
substantially reduced by the presence of organic
matter.
72

73. 73

74. 74

75. Virgin females were taken from roots.
Surface dried with filter paper placed between the ends
of two glass capillary tubes filled with distilled water.
The female body separated the capillaries with the head
in one and the tail in the other.
The open ends of the capillaries were sealed with
Silicone Fluid
After 18 hours the capillaries were removed and their
contents bio assayed. 75

76. a: The arrangements of roots and females on agar
plates. Left with vulval secretions isolated, right with
vulval secretions touching the agar.-
b : The position of capillary tubes over the head and
tail of a female.
A, agar: R, root: V, vulval secretion : S, sealing fluid : W, water.
76

77. Results
• Females of H. schachtii and H. rostochiensis secrete
male attractant all over the body.
• More attractant is secreted around the tail of
H. schachtii females than around the head, so the
egg sac can act as a carrier of the pheromone
whereas the small egg sac of H. rostochiensis does
not.
77

78. 78

79. 79

80. 80

81. 81

82. • Ascarosides, are produced not only by a plant-
parasitic nematode, but also by vector beetle.
• Ascarosides secreted by the dispersal third-stage
nematode LIII larvae promote beetle pupation by
inducing ecdysone production in the beetle and
upregulating ecdysone-dependent gene expression.
82

83. 83

84. • Once the beetle develops into the adult stage, it
secretes ascarosides - dispersal fourth-stage
nematode LIV larvae, potentially facilitating their
movement into the beetle trachea for transport to
the next pine tree.
• Ascarosides play a key role in the survival and
spread of pine wilt disease.
84

85. 85

86. 86

87. 87

88. 88

89. 89

90. • Comparisons of two bioassays, an agar plate method
and a sand slide method.
• The gradient established by the pheromone could travel
30 mm, with a net positive movement of males to the
pheromone at 27-66% and 85-90%, respectively.
90

91. Percent of positive movement of
Heterodera glycines – Various
combinations
Males Females Agar plate Sand slide
3 3 66 % 93%
3 4 60%
3 5 56% 87%
4 4 41%
4 3 96%
4 5 85%
5 5 40%
5 3 40%
5 4 38%
91

92. 92

93. 93

94. • Lectin binding sites on the surface of Meloidogyne
sp. - lectins conjugated to fluorescein
isothiocyanate or colloidal gold.
• The amphidial exudate, histochemically to contain
carbohydrate, was the principal binding site.
• Species and race specific binding patterns were
observed for both amphidial and cuticular binding
sites. 94

95. 95

96. • Both exosporia and spore fragments of P.
penetrans - capable of host-specific
attachment to the cuticle of M. incognita, a
root-knot nematode host.
• Putative M. incognita receptors appear to be
soluble in β mercaptoethanol (BME).
• The juvenile cuticle components involved in
attachment are also BME-soluble, suggesting
that they might be collagens, and are sensitive
to trypsin and endoglycosidase.
96

97. 97

98. • A single compound with sex pheromone activity -
isolated from the female soybean cyst nematode,
Heterodera glycines.
• A sequence of HPLC - identified as vanillic acid.
• Both attractancy and coiling behavior - elicited.
98

99. • Nematode parasitism is initiated when
P. penetrans endospores attach in a host- and
stage-specific manner to the cuticle of
nematodes.
(Sayre, 1980)
99

100. 100

101. • The bacterium Pseudomonas oryzihabitans
symbiotically associated entomopathogenic
nematode Steinernema abbasi, is particularly
effective against root-knot nematodes.
• The bacterium have colligative stimulation in
the simultaneous presence of tomato root tip
exudates and J2 of M. javanica
101

102. • The surface of the J2 appears to contain
carbohydrate recognition domains probably
not collagen - interact with
N-acetylglucosamine on the spore surface
which are linked to either glycoproteins or
peptidoglycans.
(Davies, 1993)
102

103. 103

104. 104

105. 􀅏Learning about how nematodes
communicate opens up new possibilities
for prevention of nematode infection in
humans and nematode control in
agricultural settings said co author
Frank Schroeder a Cornell adjunct
assistant professor of chemistry and
chemical biology and at scientist at BTI an
independent alliate of Cornell
105

106. 106

107. Conclusion
• Plant, animals and pathogens share elements
such as fatty acids, proteins, neurotransmitters
and in some of the signalling machinery
underlying responsiveness to the environment.
• Understanding the signalling & perception
processes occuring in the interactions will reveal
targets for chemical or genetic intervention.
107

108. References
108
• Leontopoulos, S., Petrotos, K., Anatolioti, V., Skenderidis, P.,
Tsilfoglou, S., & Vagelas, I. (2017). Chemotactic Responses of
Pseudomonas oryzihabitans and Second Stage Juveniles of
Meloidogyne javanica on Tomato Root Tip Exudates. International
Journal of Food and Biosystems Engineering, 5(1), 75-100.
• Persidis, A., Lay, J. G., Manousis, T., Bishop, A. H., & Ellar, D. J.
(1991). Characterisation of potential adhesins of the bacterium
Pasteuria penetrans, and of putative receptors on the cuticle of
Meloidogyne incognita, a nematode host. Journal of Cell Science,
100(3), 613-622.

109. 109
• Perry, R. N. (1996). Chemoreception in plant parasitic nematodes.
Annual review of phytopathology, 34(1), 181-199.
• Zuckerman, B. M., & Jansson, H. (1984). Nematode chemotaxis and
possible mechanisms of host/prey recognition. Annual Review of
Phytopathology, 22(1), 95-113.
• Riddle, D. & Bird, A. (1985). Responses of the plant parasitic
nematodes Rotylenchulus reniformis, Anguina agrostis and
Meloidogyne javanica to chemical attractants. Parasitology, 91(1),
185-195.
• Zwaal, R.R., Mendel, J.E., Sternberg, P.W., and Plasterk, R.H.
(1997). Two neuronal G proteins are involved in chemosensation of
the Caenorhabditis elegans Dauer-inducing pheromone. Genetics
145, 715–727.

110. Thank you
110