BB30129: Wound signalling (Hans)
Note: Hans emphasised standard signalling principles that are common to
different pathways we have covered. E.g. calcium signalling,
phosphorylation, etc.
Wound signalling
Numerous organisms consume plant material to obtain energy. These
include:
Herbivores e.g. pandas eat bamboo
Herbivorous insects e.g. larva of hawkmoth Manduca sexta feed on
thorn apple fruit Datura wrightii
Root nematodes e.g. soybean root cyst nematode infects soybean
roots, attaching to vascular tissue and consuming plant material.
Then emerges from infected root.
Two types of wound defence mechanisms employed by plants:
Constitutive defence mechanisms: preformed resistance traits,
always expressed. These include:
a) Physical barriers – thorns, trichomes, resins, etc.
b) Chemical defence compounds – e.g. proteinase inhibitors (small
molecules that inhibit digestion of plant by predator by inhibiting
the proteinases produced by herbivores to degrade plant proteins)
& toxins (small molecules like alkaloids, phenolics, cyanogenic
glycosides – deleterious/lethal effects on predators)
Wound-induced defence mechanisms: only triggered upon detection
of plant wounding. These include:
a) Local & systemic production of a range of chemical defence
compounds – locally at site of injury or systemically across
widespread/distant plant regions
b) Production of volatile signals that attract predators/parasitoids of
the herbivore
Fitness costs:
Constitutive defence – high energy outlay (costly) but provides good
resistance against wounding (prevents injury)
Wound-induced defence – low energy outlay (not as costly) but
provides incomplete resistance (does not prevent injury)
We will be concentrating on wound-inducible defence mechanisms,
however, many of the defence compounds produced during these are the
same as in constitutive defence mechanisms.
, Wound-induced defence mechanisms
Wound responses occur within minutes-hours:
plant rapidly detects signals of wounding and
triggers a response.
They can occur locally (at the site of injury) and
systemically (wounding in one region is signalled
to distinct plant regions to induce a widespread
response – proteins and proteinase inhibitors
accumulate in distant tissues).
Repairs damaged tissues and prevents further
damage to the plant.
How are wound-induced responses made specific
to different insults?
1. Elicitors
Compounds from herbivores that come into contact with plant cells and
act as wound signals – usually oral secretions
Enzymes: β-glucosidase (produced in cabbage white caterpillar
saliva), glucose oxidase (corn earworm, European corn borer).
Fatty acid amino acid conjugates (FACs) e.g. Manduca sexta
Bruchins (long chain diols) in oviposition fluid of Bruchidae pea &
bean weevils
EXTRA: how plants distinguish herbivorous vs. mechanical wounding
Plants have evolved the ability to perceive HAMPs (herbivory-
associated molecular patterns) which have 2 categories:
1) Chemical elicitors derived from herbivore oral secretions and
oviposition fluids
2) Elicitors that originate from the specific patterns of wounding
Several elicitors from oral secretions are identified as triggering
responses to herbivory.
-- A glucose oxidase (GOX) isolated from Helicoverpa zea oral
secretions, and acts to suppress plants’ defence responses.
-- HPLC (high performance liquid chromatography) separation of oral
secretions from armyworm (attack cowpea plants) revealed the
peptide inceptin to trigger defence response. Inceptins are
proteolytic products of plant chloroplastic ATP synthase – this
protein is digested within the armyworm to produce inceptins.
Many herbivorous insects lay eggs on plants – oviposition fluid also
contains elicitors.
-- Benzyl cyanide (BC) isolated from oviposition fluid elicits defence
responses in brussel sprouts plants that arrest he egg parasitioid
Trichogramma brassicae.
Note: Hans emphasised standard signalling principles that are common to
different pathways we have covered. E.g. calcium signalling,
phosphorylation, etc.
Wound signalling
Numerous organisms consume plant material to obtain energy. These
include:
Herbivores e.g. pandas eat bamboo
Herbivorous insects e.g. larva of hawkmoth Manduca sexta feed on
thorn apple fruit Datura wrightii
Root nematodes e.g. soybean root cyst nematode infects soybean
roots, attaching to vascular tissue and consuming plant material.
Then emerges from infected root.
Two types of wound defence mechanisms employed by plants:
Constitutive defence mechanisms: preformed resistance traits,
always expressed. These include:
a) Physical barriers – thorns, trichomes, resins, etc.
b) Chemical defence compounds – e.g. proteinase inhibitors (small
molecules that inhibit digestion of plant by predator by inhibiting
the proteinases produced by herbivores to degrade plant proteins)
& toxins (small molecules like alkaloids, phenolics, cyanogenic
glycosides – deleterious/lethal effects on predators)
Wound-induced defence mechanisms: only triggered upon detection
of plant wounding. These include:
a) Local & systemic production of a range of chemical defence
compounds – locally at site of injury or systemically across
widespread/distant plant regions
b) Production of volatile signals that attract predators/parasitoids of
the herbivore
Fitness costs:
Constitutive defence – high energy outlay (costly) but provides good
resistance against wounding (prevents injury)
Wound-induced defence – low energy outlay (not as costly) but
provides incomplete resistance (does not prevent injury)
We will be concentrating on wound-inducible defence mechanisms,
however, many of the defence compounds produced during these are the
same as in constitutive defence mechanisms.
, Wound-induced defence mechanisms
Wound responses occur within minutes-hours:
plant rapidly detects signals of wounding and
triggers a response.
They can occur locally (at the site of injury) and
systemically (wounding in one region is signalled
to distinct plant regions to induce a widespread
response – proteins and proteinase inhibitors
accumulate in distant tissues).
Repairs damaged tissues and prevents further
damage to the plant.
How are wound-induced responses made specific
to different insults?
1. Elicitors
Compounds from herbivores that come into contact with plant cells and
act as wound signals – usually oral secretions
Enzymes: β-glucosidase (produced in cabbage white caterpillar
saliva), glucose oxidase (corn earworm, European corn borer).
Fatty acid amino acid conjugates (FACs) e.g. Manduca sexta
Bruchins (long chain diols) in oviposition fluid of Bruchidae pea &
bean weevils
EXTRA: how plants distinguish herbivorous vs. mechanical wounding
Plants have evolved the ability to perceive HAMPs (herbivory-
associated molecular patterns) which have 2 categories:
1) Chemical elicitors derived from herbivore oral secretions and
oviposition fluids
2) Elicitors that originate from the specific patterns of wounding
Several elicitors from oral secretions are identified as triggering
responses to herbivory.
-- A glucose oxidase (GOX) isolated from Helicoverpa zea oral
secretions, and acts to suppress plants’ defence responses.
-- HPLC (high performance liquid chromatography) separation of oral
secretions from armyworm (attack cowpea plants) revealed the
peptide inceptin to trigger defence response. Inceptins are
proteolytic products of plant chloroplastic ATP synthase – this
protein is digested within the armyworm to produce inceptins.
Many herbivorous insects lay eggs on plants – oviposition fluid also
contains elicitors.
-- Benzyl cyanide (BC) isolated from oviposition fluid elicits defence
responses in brussel sprouts plants that arrest he egg parasitioid
Trichogramma brassicae.
