Deadly Chemistry Flashcards
How are the two different types of plant structure called, that are involved in „shooting“ out chemicals
Lacticifers
Resin ducts
What are Lacticifers?
Produce and store latex
What is latex?
A water soluble emulsion containing highly polymerized terpenes as well as proteins
What do lactifers consist of?
A single cell, several centimeters longwhich may be branched or unbranched
What happens when a lactifer is damaged?
The latex oozes out and gets sticky bc it is exposed to air
What are cardenolides in milkweed latex?
Toxins
They inhibit Na+/K+ ATPases (cation pump that is responsible for transporting NA+ out of the cell and K+ into it)
When insects feed on it they becomecataleptic
What can lactifers be?
Living cells
Resin ducts
Secretory canals#
Intercellular spaces which develop through seperation or breakdown of cells
What are Ecdysteroids?
Steroidal hormones present in all classes of arthropods
They regulate aspects of development, meetamorphisis and reproduction
What are arthropods?
An insect
How are insects able to produce their steroid hormones?
They cant produce their own steroid nucleus
To do so they need to obtain cholesterol and sitosterol from their diet
This allows moulting
What are Brassica tissues?
Tissues in cabbages containg mustard oil
Where are glucosinolates kept in brassica tissues?
Seperate from the enzyme responsible for breaking them down - myrosinase.
If an insects feeds on it, they contact -> isothiocyanates and nitrils get released
The mixture of those is toxic
Are glucosinolates only released by feeding?
Some of them are on the leaf top
Why are glucosinolates on the leaf surface?
As a first line of plant defence
Deterring non specialist insects and pathogens
What are saponins?
triterpenoid compounds that are antimicrobial that also act as feeding deterrents
What is the major glucosinolate in cabbages?
Sinigrin which forms mustard oil ( allyl isothiocyanate) when hydrolysed by myrosinase
How is the formation of mustard oil by herbivores chewing called?
Mustard oil bomb mechanism
What is a avirulent?
A microbe that is unable to cause disease
What happens when we oculate a plant with an avirulent?
The plants get resistant to the virulent corresponding as well -> All the plant tissues are resisitant, not only the inoculated one
How many phytoalexins have been identified?
Over 300 (2015)
What is a phytoalexin?
A plant defence compound
What distinguishes Phytoalexins from different antimicrobial compounds
They are only made and accumilated following attack
What are Phytoancipins?
Antimicrobial compounds that are present in the plant before attack or ones made after attack but only using pre-existing constituents
How much less phytoalexins do resistant plant accumilate?
Less than one third of the amount of a susceptile variety
They also accumilate faster in a resistant plant
What are roles of serotonin in plants?
Senescence
Flowering
Plant defence (Phytoalexin)
How does the hypersensitive response (HR) work against fungi?
The plant that is resistant to the fungi, kills of cells that are attacked by it, thereby killing the fungi as well
How do fungi use the HR for their gain?
Only works for necrotrophs: they trigger HR in attacked cells, and feed on them
What are hemibiotrophs?
Pathogens that start as biotroph but convert into a necrotoph
What is to be said about dead cells?
They often contain a lot of antimicrobial compounds
These chemicals are made both by the attacked cells before they die and by the surrounding cells
Is programmed cell death only part of a defence response?
It is an important part of plant development occuring for example in the fomation of xylem vessels
How do viruses multiply?
They hijack the plants genetic machinery, getiing it to replicate thei RNA(DNA for some viruses)
During the replication, viral RNA accumilates
What determines the specificity in the RNA silencing machanism?
Antisense RNA -
How does gel electrophoresis work?
It seperates macromolecules (DNA, RNA and Proteins) according to size and charge
Samples are placed at the bottom of the gel and an electric current is applied
Negatively charged nucleic acid molecules move through the gel - shorter molecules move faster and are further up the gel than bigger ones
How exactly does RNA silencing work?
- Virus double stranded RNA is set upon by plant enzymes known as dicer proteins
- The dicer proteins (enzymes) cut the viral double stranded DNA into specific fragments of between 21 and 24 nucleotides in lenght (siRNA)
3.These two strands of siRNA are seperated and one of these strands becomes incorporated in the RNA induced silencing complex
4.In this complex are two enzymes - one binds the RNA strand, the other one (a nuclease) degrades the RNA
Using the RNA strand as a template, the binding enzymes bind the complimentary nucleotide sequence
5.The viral RNA molecules are then degraded
-> this suppresses the accumilation of viral RNA
Why is the RNA silencing mechanism in plants?
It is a potent defence mechanism that is effective against rapidly replicating viruses
Because the complex is targeting siRNA derived from virus RNA, it is specific for viral RNA and the hosts RNAs are not affected
The silencing signal is mobile, it moves with the virus so it cannot escape the silencing even when it moves
How do viruses overcome the RNA silencing complex?
A suppressor from the tomato bushy stunt virus binds directly to the dsRNA molecules, preventing them to be incorporated into the RNA induced silencing complex
Other viruses may disrupt RNA silencing by interfering with the function of the dicer-like enzyme
What are siRNAs good for except virus resistance?
Bacterium resistance
microRNA regulates plant defence
What is the circadian rhythm?
The rhythm that determines the sleeping and eating patterns of an organism
Is the circadian rhythm a response to light or temperature changes?
No
They are capable to measure 24h intervalls
What genes depend on the circadian rhythm?
Stomata opening
Spore production
Defence production such as jasmonic acid (during the daytime)
