Med bot quiz deux Flashcards
Constitutive vs induced defenses?
“constitutive defenses” are protective mechanisms that are always present, regardless of an attack, while “induced defenses” are only activated in response to a threat like herbivory or pathogen infection
Induced responses differ by type of attack, give 2 examples:
chewing herbivores vs. pathogens
Herbivore response centers on what?
the jasmonic acid (JA) signaling cascade
Pathogen response centers on what?
hypersensitive response, phytoalexins, and salicylic acid (SA) signaling cascade
Elicitors are
hybrid herbivore-plant molecules that signal herbivory damage (and can tell plant about identity of specific herbivore)
Fatty acid amides = what are, and what do for le plant?
fatty acid from plant + amino acid from insect gut
Initiate downstream defenses in plant
In what way is jasmonic acid important? Who does it primarily effect?
(bonus for what type of defense)
JA is an essential signal in both local and systemic herbivory response, primarily through its effect on gene transcription
(herbivory defense)
Linolenic acid is what and from what?
a fatty acid derived from membrane lipids
Cyclized in chloroplast, then further hydrolyzed in peroxisome by β-oxidation pathway (which is also involved in hydrolysis of fats)
JA mechanism of acion (god bless you brave soldier)
1) JA is conjugated to isoleucine (an amino acid) by JAR1
2) JA-Ile binds to SCF-ubiquitin complex
3) JA-Ile-SCF complex targets JAZ repressor (of other transcription factors) protein, which is then degraded
4) With no JAZ, MYC2 and other transcription factors can initiate transcription of defense genes
Biosynthesis enzymes of all major secondary metabolite pathways
1) α-amylase inhibitors:
2) lectins:
3) protease inhibitors
4) JAZ
α-amylase inhibitors:
inhibit insect amylases that break down starch
protease inhibitors:
block enzymes that break down plant proteins
lectins:
proteins that bind to carbohydrates and epithelial cells of the insect’s gut
Plants use volatile chemicals in defense- why??
Signal to predators and parasites of herbivores
Also signal to self and neighboring plants to induce jasmonate response
JAZ:
interestingly, JA signal initiates JAZ transcription. Remember that JAZ is a repressor protein of JA-induced genes.
What kind of feedback is at play here?
(negative feedback loop to make sure JA doesnt happen too long)
Examples of volatile plant chemicals
Various low-molecular-weight compounds (terpenoids, phenolics, and alkaloids, as well as green leaf volatiles = aldehydes, alcohols, and esters)
**review slide 12
yeaa know the rough roder/idea
What are saponins? What type of defense is this?
pathogen defense molecules, look like honeycomb,
constitutive defense,
binds to sterols on fungal membranes
Receptors for pathogen-specific proteins – can also be considered a type of
elicitor
MAMP =
What are and what for?
microbe-associated general molecular pattern
Very general receptors that recognize broad groups such as oomycetes or flagellated bacteria
R genes
what are and what for?
(R for resistance):
recognize more specific markers from a given pathogen, sometimes even strains within a species
Activation of MAMP and R genes receptors initiates what and who is most important in that
signaling cascades: most important seem to be Ca2+, salicylic acid, and production of phytoalexins
hypersensitive response-
Ca2+ signals nitric oxide and reactive oxygen species production →
The hypersensitive response does what?
This is a kind of a “nuclear option” that kills cells locally, both plant and pathogen
Followed by production of lignin and callose in cell walls of healthy cells = barrier to further infection
