Call To Arms Flashcards
On what does the type of the warning signal in a plant depend?
On the nature of systemic resistance
What are biotrophs?
Attackers that need to keep the plant alive
What is the hypersensitive response?
The suicide of a cell in order to kill off the invader
What is SAR?
Systemic acquired resistance
When distant plant tissues that are not under attack yet are put on alert.
One signaling molecule is salicylic acid
What is ISR?
Induced systemic resistance
Is like a vaccine
Example for an ISR
When lower leaves of a tabacco plant are inoculated, the other parts of the plant are resistant to the pathogens
How was it possible to undermine the assumption that salicylic acid is the mobile signal in plant defence?
By adding a gene to the plant that degrades salicylic acid. Experiments have shown that plants with that gene were still able to develop SAR
What is the signal responsible for alerting distant tissues in tomato plants?
Methyl jasmonate
What happens when one plant is treated with methyl jasmonate?
Other plants that have not been treated with it also accumilated the defensive proteinase inhibitors. The methyl jasmonate volatilized and acted as an airbone signal
Are the defences activated by jasmonic acid?
No, but by modified forms of it, by which it is conjugated to amino acids
One of it being jasmonoylisoleucine (JA-Ile)
What exactly happens when a leaf is wounded by insect attack?
- Jasmonic acid is synthesized (within 30 sec at wound site, followed just 15 seconds later by accumilation of jasmonic acid at undamaged sites near the wound)
2.JA-Ile is synthesized - Defences get activated
Why do herbivores often consume small amounts of a leaf before they go to the next one?
Because the jasmonic acid gets synthesized
How fast does the wound signal travel?
3 - 8cm per minute
What are WASPs?
Wound activated surface potential changes
electrical signals that are produced upon wounding and the activation of defences
When do WASPs occur?
Only when larvae is feeding on the leafs, not when they walk over it
How fast do these signals travel?
9cm per minute
What happens when the electrical signals are received at sites?
The defences get turned on
How are these electrical signals generated?
By glutamate receptor like (GLR) ion channels
How does the electrical signaling work?
When an insect herbivore munches on a leaf, the signal is transmitted to other leafs where jasmonic acid is produced, which activates defences
How is this electrical wave generated?
By a continous relay of cell-membrane depolarization
What are one of the messengers triggered rapidly in cells?
Calcium
What is calcium important for in plants defences?
Signal transduction
What signals are transmitted between plants that cant talk otherwise?
Volatile signals
How were volatile signals proven?
They put plants in a chamber where they were damaged. They let the air flow in a chamber next to it, and plants got their defences ready
How is this air signal called?
Volatile plant communication
What are volatile signals good for too?
To attract predators of herbivores
Can volatile „cocktails“ vary?
Yes, depending on the insect feeding on the differet plants
Even different varieties of the same plant can release different volatile blends
Is volatile communication possible between different plant species?
Yes! f.e. Sagebrush and tabacco plants
How do these cocktails vary?
Even when the same insect is feeding on different plants
Do the herbivores react to specific parts of the volatile cocktail?
It is believed that they react to the cocktail as whole
Are these volatiles only used to attract?
No, they can also repell insects looking to lay eggs
What are oak apples?
Galls that form on oak trees. Wasps are responsible for it
What are galls good for for insects?
Accomodation
Shelter
Protection
Food
How does the gall inducing fly protect itself?
When it attacks a plant, the plant is unable to send out volatile signals
They can also use the volatile signals to ward off their own enemys
How do aphids use pstacchio tree defence?
They induce galls on the tree - in the process, the plant releases a volatile signal that acts as a goat deterrent.
These goats dont eat the leaves anymore, protecting the aphids
Why are insectivourous birds attracted to damaged trees?
birds can react to volatile cues
What is the maximum distance for volatile communication of trees?
50cm. The plant mainly talks to itself
How do alarmsignals travel inside the plant?
Via its vascular system - but it will only reach leaves or branches with a direct connection to the attacked leaf
Volatile signals can help to induce a defence activation in other parts of the plant
What are the major players in plant defence?
Salicylic acid and jasmonic acid
What are pathogens that kill plant cells called?
Necrotrophs
Which plant hormones are crucial in plant defence?
Ethylene
Auxin
Cytokinin
Absicisic acid
What is reffered to as hormonal crosstalk?
Antagonistic and synergistic interaction between hormones
This helps the plant to fine tune its response to the attacker
What does a crosstalk between salicylic acid and jasmonic acid provide the plant with?
It helps to prioritize the right pathway - depending on the nature of attack
How do insects overcome plant defences
They like to eat parts of the plant that havent been primed
