Baker Plant signalling Flashcards
How does plant development differ from animals?
No cell migration,
Meristem tissue retains ability to differentiate
How do plants adapt to environment?
biochemically and physically
What are the 4 types of meristem?
shoot apical
auxillary
lateral
root apical
What are the main targets of signalling?
transcription factors, enzymes and cytoskeleton
What structure are plant hormones?
aromatic/conjugated small organics or peptides
What cell properties are affected by signalling?
Spatial differentiation of tissues, cells and within organs
polarity
growth rates
Where are hormones produced?
all cells
Where do plant hormones act?
On their own/different cells with a pleiotropic effect
How are plant hormones regulated?
locally-no CNS
What are the classic hormones?
Auxins Cytokinins gibberellins absisic acid ethylene
What are jasmonates involved in?
carbon partitionning mechanotransduction senescence reproductive development stress resposes
How do jasmonates respond to biotic stress?
upregulate production of protease inhibitors to deter herbivore
produce volatile compounds to attract parastiods and prime adjacent plants
What is an example of a volatile compound produced in response to biotic stress?
meJA
How are Jasmonates produced?
alpha linoleic acid release by phospholipases 13-(S)-HPOT by 13-lipoxogenase allene oxide by AOS cis-(+)-OPDA by AOC export into peroxisome activartion by OPR3 3 Beta oxidation export to cytoplasm conjugation
Where are jasmonates released from the membrane?
chloroplast
What are the JA animal cell analogs?
prostaglandins
How are JA stored?
Conjugation to amino acids or methylation
Which amino acid is JA mostly conjugated to?
isoleucine
What are modified JAs known as?
oxylipins
How is JA imported into the peroxisome?
Mostly by ABC transporter but some ion trapping
Which ABC transporter imports JA?
Class D comatose
Which compound mimicks JA-Ile?
coronatine bacterial toxin
What are the biosynthesis mutants for JA?
Orp3 (OPDA activation)
Fadd triple mutant (no alpha-linoleic acid)
cts1/2 import mutants
What characteristics do JA mutants have?
male sterility and increased susceptibility to disease
Which type of JA mutant is reversible?
biosynthesis
What is the JA response mutant?
coi1
What does coi1 encode?
SCF F box specificity of E3 ubiquitin ligase
What is the mechanism of JA activation?
JA-Ile acts as SCFcoi1 F box
binds JAZ (repressor) to promote E3 ubiquitination
genes are expressed
What characteristics do coi1 mutants have?
male sterility,
increases susceptibility to disease
resistance to bacterial toxins and MeJA
What do the auxin family control?
tropic growth, apical dominance organogenesis pattern formation polarity
How are auxins produced?
Derived mostly from tryptophan in a series of interlinked pathways under development and environmental control
Which enzymes are involved in synthesising auxins?
Aminotransferases, decarboxylases and oxidases
What is the main natural auxin?
indole-3-acetic acid
Why are synthetic auxins used?
More stable
How are auxins stored?
Conjugated through an ester bond to sugars
How are auxins transported?
Through phloem for fast, non polar transport
Through cells using carrier proteins for polarity
Which proteins transport auxins?
AUX1 influx, PIN efflux
PGP4 influx, PGP1 efflux
How does AUX1 transport auxins?
As ions with H+ down a concentration gradient from pH5.5 to pH7
How do plant cells maintain the H+ gradient?
P class ATPase
Where are PINs found in respect to AUX1?
opposite site of cell
What is the positionning of PINs in a root tip?
PIN1 and 4 bring auxins down centre
PIN3/7 act as quiescent centre
PIN2 transports up edge cells
Is PIN distribution constant?
No, changes during development and in response to environment
How is PIN expression controlled?
Synthesis in ER and transported in vesicles to plasma membrane.
Clathrin mediated endocytosis consitutively recycles
Degraded in the vacuole
What determines location of PINs?
phosphorylation
How is endocytosis stopped?
high [auxin]
How are gravity tropisms produced?
Gravity detected by statolit starch granules. PIN3 redistributes from all over cell to basal membrane and cells change shape/ grow assymetrically to restore vertical
How does auxin cause gene expression?
Binds aux/IAA repressor as the SCF-TIR1 F box unit of ubiquitin ligase. Repressor degraded and ARF promoter activated
How many mutants with no auxin have been discovered?
None
