swagat ppt

1. Presented by
Ravi Kumar
I’d. No. – CA 12057/2021
Ph.D.
Plant Pathology

2. Symbiosis

3. Mutulism

4. Comensalism

5. Amensalism

6. PARASITISM
The removal of food by a
parasite from its host is called
parasitism.
An organism that lives on or in some
other organism and obtains its food
from the latter is called a parasite
PARASITE
Fungi, Nematoes,
Bacteria, Parasitic Plants
etc.

8. PARASITIC PLANTS
•
•
Plant that obtains all or part of its nutrition from
another plant (the host) without contributing to the
benefit of the host and, in some cases, causing
extreme damage to the host.
Approximately 4,500 parasitic species belonging to 28
families, representing 1% of the dicotyledonous
angiosperm species, have been reported as parasitic
plant.

9. Classification
Stem
Parasite
Root
Parasite
Holo Stem
Parasite
Hemi Stem
Parasite
Holo Root
Parasite
Hemi Root
Parasite
On the basis of site of attachment

10. On the basis of on host dependency
Obligate Parasite Facultative Parasite
Stem
Parasite
Root
Parasite
Holo
Parasite
Hemi
Parasite
Holo
Parasite
Hemi
Parasite
Root
Parasite
Hemi
Root
Parasite

11. Hemi parasite Vs Holo parasite

12. Dodder (Cuscuta spp.)
Family- Convolvulaceae
Genus- Cuscuta
>150 Spp. Are reported
Other names- Amarbel, Devil’s hair
etc.
Degenerated leaves
Photosynthesis absent
Spread through- Contaminated seed,
movement of Soil equipments,animals
and some spp. by water.
Host- Tomato, Potato, Soybean,
Cotton, Alfalfa, Roses,
Chrysanthemums, Carnations etc.

13. Mistletoe (Viscum spp.)
Family- Loranthaceae
Genus- Viscum
Other names- Loranthus, Bana, Banar,
Banah, Dharua and Parjeevi etc.
 True leaves
Root system absent
Photosynthesis take place
Spread through- Contaminated seed,
movement of Soil equipments,animals
and some spp. by water.
Host- Mango, Coffee, Baniyan
tree, Citrus, Walnut, Barberry, Ber
and other plantation crops.

14. Orobanche (broomrape)
Family- Orobanchaceae
Genus- Orobanche
 Other names- Tokra, Vakumba,
Bambaku, Pokayilaikalan, Bodu ,
malle.
 Root system absent
 Photosynthesis does not take place
 Single plant produce about
100000 seed
Host- Sunflower, Tobacco,
Tomato, Eggplant, Cabbage and
other plants of solanaceous and
crucifer crop.

15. Striga (Witchweed)
 Family- Orobanchaceae
 Genus- Striga
Root system absent
 Photosynthesis take place
 Witchweed produce 50,000 to
500,000 seed/plant (12-40 yr)
 Dispersal through human
activity, machinery, tools and
clothing.
 Host- Sugarcane, Maize,
Cereal, Millets etc.

16. Triphysaria spp.
 Family- Scrophulariaceae
 Genus- Triphysaria
Other name- Yellowbeak owl's-clover
Root system present
 Photosynthesis take place
 Witchweed produce 50,000 to
500,000 seed/plant (12-40 yr)
 Dispersal through human activity,
machinery, tools and clothing.
 Host- Sugarcane, Maize, Cereal,
Millets etc.

17. Phtheirospermum spp.
 Family- Orobanchaceae
 Genus- Phtheriospermum
Other name- Kanak
Champa, Muchakunda or
Karnikar tree
Root system present
 Photosynthesis take place

18. Germination
• Strigolactones (SLs) (e.g. Sesquiterpene) are the best-
characterized class of germination stimulants.
• At least 20 different SLs molecules have been identified in
plants by which parasite seeds are able to differentiate among
hosts on the basis of the identity of exuded SLs.
• Function-
1. Endegeneous hormon to control Plant development
2. Promote relationship between prasitic plants and host

20. PARASITE IDENTIFICATION OF HOSTS
Strigolactones (SLs) are the best-characterized
class of germination stimulants for members of the
Orobanchaceae
Cuyper et al., 2017

21. The KAI2 genes in parasitic
Orobanchaceae
diverged KAI2
Provides Parasites with a mechanism to
1. Recognize specific host SLs,
2. Adapt to changes in host SL
profiles,
3. Shift to recognize new hosts
expansion and
specialization
Parasitic plants use a protein related to D14
termed KARRIKIN INSENSITIVE 2 (KAI2;
also known as HYPOSENSITIVE TO
LIGHT)

22. MODE OF ACTIONOF STRIGOLACTONES
Binding of SLs to the KAI2 protein
D ring is cleaved from the fused ABC
ring
Covalent binding of d ring to KAI2 protein
resulting in germination promotion of seeds
Cuyper et al., 2017

23. Clarke et al., 2019

24. Locating the Host
Chemotropic growth of
the parasite radicle in
Orobanchaceae and
Cuscuta has been
postulated.

26. "Runyon et al., (2006) conducted an experiment and reported that some
volatile chemicals, such as ß-phellandrene, ß-myrcene and α-pinene,
released by host plants (tomato and wheat), help Cuscuta to locate its host
plant."

27. Prehaustorium formation [Induced by
haustorium inducing factors (HIFs)]
Haustorium maturation

28. What is HIFs?
Chemicals released by host plants stimulating
production of haustorial connection in
parasitic plants
 Flavonoids
 Phenolic acids
 Quinones
 Cytokinins
 Cyclohexene oxides

29. Recognition of HIFs by parasitic roots/radicles
Radicals start to show morphological changes
Semispherical shaped prehaustorium are
formed within a few days

30. Haustoria maturation
Haustorium reaches the host tissues, the
epidermal cells of the haustorium apex
differentiate into intrusive cells
Intrusive cells grow inside host tissue towards
host vasculature
Some adjacent parasitic cells differentiate
into tracheary elements and form xylem
bridge

31.  Orobanche and Phelipanche do not form obvious haustorial
structures in response to DMBQ.
 They form haustoria when treated with root exudates of Brassica
napus.
T. versicolor forms haustoria in
response to DMBQ, but Triphysaria
eriantha does not
Not all Orobanchaceae
respond to the same
HIFs

32. Chang et al., 1986
The first HIF identified : 2,6-dimethoxy-1,4-
benzoquinone (DMBQ)

33. Pérez-de-Luque, 2013

34. Birschwilks et al.,
2006

35. 35

36. Attachment via Haustorial Hairs
The first contact between certain Orobanchaceae parasites and
hosts is made by haustorial hairs, which cement the parasite to
the host.
When host and parasite roots were forced to grow closely
together, haustorial hair mutants produced similar numbers of
haustoria as do wild-type P. Japonicum. Thus, haustorial hairs
may play a role in host–parasite associations but not in
haustorium initiation.
Clarke et al., 2019

37. HORMONE ACTION
 Auxin :
 Stimulate haustoria development
 Cytokinin :
 Act as HIF
Kinetin (a synthetic cytokinin)
6-benzylaminopurine (BAP)

38. Material transfer
Water and Nutrients :-
 Xylem–xylem connections - Striga spp.
 Phloem–phloem connections - Orobanche spp
 Hyaline body - Striga, Alectra, Lathraea and
Rhinanthus
 Paratracheal parenchyma around the XB - T.
versicolor, P. japonicum and Orobanche

39. Parasite–host exchange of RNAs :-
mRNAs are bidirectionally transfered between cuscuta and their
hosts
 Arabidopsis–C. pentagona interaction- 1% of mRNAs from the host
to the parasite & 0.6% from the parasite to the host through
haustoria.
 Tomato–C. pentagona interaction – RNAs transferred through the
phloem.
Horizontal Gene Transfer :-
Exchange of genetic component (Bidirectional)
• Mitochondrial HGTs
• Chloroplast & Nuclear HGTS (Rare)
 Rafflesiaceae plants – 24-41% mitochondrial HGTS
 P. aegyptiaea- legume – albumin 1 KNOTTIN like protein
(Nuclear HGTS)

40. Kaiser et al., 2015

41. (a) No or reduced production of germination stimulant(s).
(b) Production of germination inhibitors.
(c) Delay, reduction, or complete inhibition of haustorium
formation leading to attachment incompetence, and
(d) Development of preformed mechanical or structural barriers on the
host surface to impede attachment.
Host Reaction to Attack by Root Parasitic Plants
Gressel et al., 2
2
0
6
13

42. (a) Abiosis, the synthesis and release of cytotoxic compounds (e.g., phenolic
acids, phytoalexins) by the challenged host root cells.
(b) Rapid formation of physical barriers to prevent
possible pathogen ingress and growth (e.g., lignification and other forms of
cell wall modification at the host–parasite interface.
(c) Release of reactive oxygen species and activation of programmed cell
death in the form of a hypersensitive response at the point of parasite
attachment to limit parasite development and retard its penetration.
(d) Prevention of the parasite establishing the essential functional vascular
continuity (i.e., xylem-to-xylem and/or phloem-to-phloem connections)
with the host, delaying parasite growth followed by parasite
developmental arrest and eventual death.

43. The haustorium is well developed with xylem
continuity between parasite and host; in the
resistant interaction, the haustorium invades
host root cortex but is not able to penetrate the
endodermis to establish host– parasite xylem
connectivity
Lignification of host tissue around the invading
parasite the haustorium penetrates into the
cortex but does not form connections.
root showing a xylem vessel filled with
mucilage 30 days after inoculation with O.
crenata
An unsuccessful O. crenata penetration in root
of a resistant vetch cultivar 20 days after
inoculation, showing lignification of host cells,
accumulation of a brown secreted material

44. Succeptible
Reaction
• Host derived
succeptibility
factors
• Suppression of host
immune system
Resistance
Reaction
PARASITIC
PLANT ON
HOST
Innate immunity
•ETI
•PTI

45.  Host-derived germination stimulants and HIFs.
 Components of the cell wall and cell membrane that must be
modified to form successful haustoria.
 Regulators of the plant immune system that are affected by
parasitic plants.
 Metabolic or nutrient transport genes that are hijacked by parasitic
plants to meet their nutritional needs.

46. Pre-attachment resistance includes:
 No or reduced production of germination stimulant(s).
 Production of germination inhibitors.
 Delay, reduction, or complete inhibition of haustorium formation
leading to attachment incompetence.
 Development of preformed mechanical or structural barriers on
the host surface to impede attachment.

47. Post-attachment resistance includes :
Enhanced cell wall lignification.
 Suberinization.
Modifications and structures (hairs or other outgrowths)
that retard attachment to the host.

48. Innate immunity can present as
 Abiosis ( phenolic acids, phytoalexins)
 Formation physical barriers
( lignification and cell wall modification)
 Hypersensitive response
(Release of reactive oxygen species & activation of
programmed cell death )
 Prevention functional vascular continuity
( xylem-to-xylem and/or phloem-to-phloem
connections)

49. A Place for Parasitic Plants in the Current Model of
Plant–Pathogen Interactions?
• The leading paradigm for host plant–microbial pathogen interactions
- The zigzag model (Jones and Dangl 2006)
plants and pathogens are locked in a perpetual arms race.
• Pathogen trigerred immunity :-
Pathogen produce PAMPs PAMPS identified by R-genes
Elicite an immune response

50. • Cuscuta reflexa on tomato
Parasitic plants produce ParAMPs ParAMPS identified by
CuRel receptor Elicite an immune response (Ethylene
production).
• Cowpea – S. gesnerioides Interaction :
R-gene detect a pathogen derieved effector protien & initiate
immune response.
• Orobranchae cumana on sunflower : HR reaction
• P. aegypyica – Arabidopsis mutant : perturbation of Jasmonic acid
biosynthetic signal pathway.

51. Cui et al., 2015

52. CHALLENGES IN PARASITIC
PLANT RESEARCH
The slower rate of research progress with parasitic plants
is partially due to
 The inherent problems that exist with growing and
manipulating parasites free of hosts,
 The fact that both the host and parasite are
angiosperms
 The relatively limited and only recently available high-
quality parasitic plant genomes and transcriptomes
 The difficulty or impossibility of transforming most
species of parasitic plants

53. • The discovery of parasitic plant–derived microRNAs that target host
genes.
• mRNAs are delivered via extracellular vesicles shown to carry small
RNAs that can be delivered to the fungal pathogen B. cinerea and
target Botrytis mRNAs.
• Genomic sequencing of parasitic plants combined with haustorium
cell-specifific transcriptome analyses
• Identification the genes required for parasitism and test hypotheses
about how the haustorium evolved

54. Summary
• Development of the haustorium and its interactions with the host plant are
becoming exciting areas of research, and new insights have emerged into
its role in the exchange of hormones, nutrients, and macromolecules,
including RNAs.
• Transfer of mRNA and microRNA between host and parasite appears to
be an important virulence and host adaptation strategy in Cuscuta.
• Parallels are emerging between the molecular mechanisms mediating
parasitic plant–host interactions and other plant– pathogen interactions,
including the elicitation of host innate immunity.

55. REFERENCES
• Albrecht, H., Yoder, J.I. and Phillips, D.A. (1999). Flavonoids promote haustoria
formation in the root parasite Triphysaria versicolor. Plant Physiology, 119: 585–
591.
• Birschwilks, M., Haupt, S., Hofius, D. and Neumann, S. (2006). Transfer of
phloem-mobile substances from the host plants to the holoparasite Cuscuta spp. J.
Exp. Bot., 57: 911–921.
• Asai, S. and Shirasu, K. (2015). Plant cells under siege: plant immune system
versus pathogen effectors. Curr. Opin. Plant Biol., 28: 1–8.
• Chang, M. and Lynn, D.G. (1986). The haustorium and the chemistry of host
recognition in parasitic angiosperms. J. Chem. Ecol. 12: 561–579.
• Cui, H., Tsuda, K. and Parker, J.E. (2015). Effector-triggered immunity from
pathogen perception to robust defense. Annu. Rev. Plant Biol. 66: 487–511.

56. • DeCuyper, C., Struk, S., Braem, L., Gevaert, K., DeJaeger, G. and
Goormachtig, S. (2017). Strigolactones, karrikins and beyond. Plant Cell
Environ, 40: 1691–1703.
• Furuhashi, T., Furuhashi, K. And Weckwerth, W. (2011). The parasitic
mechanism of the holostemparasitic plant Cuscuta. J. Plant Interact, 6: 207–
219.
• Kaiser, B., Vogg, G., Furst, U.B. and Albert, M. (2015). Parasitic plants of the
genus Cuscuta and their interaction with susceptible and resistant host plants.
Front. Plant Sci. 6: 45.