Transcript Signal Transduction

•Homework #1 is posted and due 9/20
•Bonus #1 is posted and due 10/25
•For Bonus points, today’s quiz is due T 9/18
DNA is used to
produce RNA
and/or proteins,
but not all
genes are
expressed at the
same time or in
the same cells.
How do cells
control which
genes are
expressed?
Protein
Cells and
organisms
must monitor
and respond
to the
environment.
Is there
anybody
out there?
Signal Transduction
External
Stimulus
Internal
Effector…
Effector
Effector
Effector
Response
Perception
(by receptor)
Stimulus
Signal transduction step by step: Perception
Signal transduction step by step: Transduction
Signal transduction step by step: Response
– such as
changes in
cellular
components
or
production of
new cellular
components
Transduction can
involve activation or
inactivation of
proteins.
Cellular responses
may involve changes
in the expression of
genes.
Blood sugar
levels as an
example of
cellular
responses to
the
environment
Why so many steps?
Multiple steps allow for signal specificity.
Different relay molecules lead to different responses
Multiple steps
allow for
signal
amplification:
Calcium is a
simple
method of
amplifying
signals
Calcium is a
common
effector.
Cytoplasmic
calcium levels
are normally
low.
During signal transduction, calcium can be
released into the cytoplasm: Perception
During signal transduction, calcium can be
released into the cytoplasm: Transduction
During signal transduction, calcium can be
released into the cytoplasm: Response
During signal transduction, calcium can be
released into the cytoplasm
General model of Ca++
signaling
General model of
Ca++ signaling
Multiple steps
allow for
signal
amplification:
Calcium is a
simple
method of
amplifying
signals
Ca++ is involved in many responses
Ca++ is involved in signal
transduction for responses of:
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in Plants
in Animals
Development
• Neurons
Cold
• Muscle movement
Guard cell closing
• Wounding
Osmotic shock
• Development
Light
• Fertilization
Fungal infection
• Hormones
Touch
• …
Pollen tube growth
Wounding…
How can there be specificity?
Everything has its
place…
Some Ca++ channels
have specific
effectors associated
with them:
Micro-domains
Ikeda, Science 12 Oct 2001 Vol 294:318-319
Root nodules: Nitrogen fixation
Bacteria and Plants Symbiosis
Signaling between bacteria and plants
1nM Nod
Fig 3. Shaw and
Long, Plant
Physiology, March
2003, Vol. 131, pp.
976–984
10nM Nod
A biphasic Ca++
response to Nod
factor:
1nM Nod - toward
nucleus
10nm Nod - away
from nucleus
1nM Nod
10nM Nod
1nM Nod
10nM Nod
A biphasic Ca++ response to
Nod factor:
1nM Nod - toward nucleus
10nm Nod - away from nucleus
Fig 3. Shaw and Long, Plant Physiology,
March 2003, Vol. 131, pp. 976–984
Everything has its
place…
2 hypotheses about
how Ca++ signals are
transduced:
Signatures vs.
Switches
Fig 1. Scrase-Field and Knight, Current Opinion in
Plant Biology 2003, 6:500–506
Photosynthesis:
Plants can make sugar
using energy from the
sun, water from the
ground, and CO2 from
the air.
Stomata regulate gas
exchange: CO2 in, O2 and
water out
H2 O
H2 O
Stomata
open
closed
Opening and closing of stomata
Ca++ fluxes in
guard cells in
response to
hormone or stress
that cause
stomatal closing.
Wildtype vs. det3
and gca2: mutants
that fail to close
stomata following
treatment
Fig 5. Sanders et al., The Plant Cell,
S401–S417, Supplement 2002
2 hypotheses about
how calcium
signals are
transduced:
Signatures vs.
Switches
Fig 1. Scrase-Field and Knight, Current Opinion in
Plant Biology 2003, 6:500–506
Ca++ is involved in signal
transduction for responses of:
•
•
•
•
•
•
•
•
•
in Plants
in Animals
Development
• Neurons
Cold
• Muscle movement
Guard cell closing
• Wounding
Osmotic shock
• Development
Light
• Fertilization
Fungal infection
• Hormones
Touch
• …
Pollen tube growth
Wounding…
How can there be specificity?
•Homework #1 is posted and due 9/20
•Bonus #1 is posted and due 10/25
•For Bonus points, today’s quiz is due T 9/18