homework #1 is posted and due 9/20 bonus #1 is posted and due 10/25
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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. - PowerPoint PPT PresentationTRANSCRIPT
•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
Protein
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?
Is thereanybodyout there?
Cells and organisms must monitor and respond to the environment.
Stimulus
Signal Transduction
Stimulus
Perception(by receptor)
EffectorResponse
Effector…
EffectorEffector
External
Internal
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:
in Plants• Development• Cold• Guard cell closing• Osmotic shock• Light• Fungal infection• Touch• Pollen tube growth• Wounding…
in Animals• Neurons• Muscle movement• Wounding• Development• Fertilization• Hormones• …
How can there be specificity?
Everything has its place…
Ikeda, Science 12 Oct 2001 Vol 294:318-319
Some Ca++ channels have specific effectors associated with them:Micro-domains
Root nodules: Nitrogen fixation
Bacteria and Plants Symbiosis
Signaling between bacteria and plants
Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984
A biphasic Ca++ response to Nod factor:1nM Nod - toward nucleus10nm Nod - away from nucleus
1nM Nod 10nM Nod
Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984
A biphasic Ca++ response to Nod factor:1nM Nod - toward nucleus10nm Nod - away from nucleus
1nM Nod 10nM Nod
1nM Nod 10nM Nod
Everything has its place…
Fig 1. Scrase-Field and Knight, Current Opinion in Plant Biology 2003, 6:500–506
2 hypotheses about how Ca++ signals are transduced:Signatures vs. Switches
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
H2OH2O
Stomata
closedopen
Opening and closing of stomata
Fig 5. Sanders et al., The Plant Cell, S401–S417, Supplement 2002
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 1. Scrase-Field and Knight, Current Opinion in Plant Biology 2003, 6:500–506
2 hypotheses about how calcium signals are transduced:Signatures vs. Switches
Ca++ is involved in signal transduction for responses of:
in Plants• Development• Cold• Guard cell closing• Osmotic shock• Light• Fungal infection• Touch• Pollen tube growth• Wounding…
in Animals• Neurons• Muscle movement• Wounding• Development• Fertilization• Hormones• …
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