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Today: Signal Transductionthe textbook has very little about signal transduction, see http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.section.2743 for more info.
Bonus #1 due in class 2/24/09
Bonus #2 due in class on 4/21/09
Five Perceptions of Genes:
1. Genes act as units of heredity
2. Genes are seen as a cause of disease
3. Genes code for proteins
4. Genes act as switches, controlling
development
5. Genes are replicators (selfish gene)
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?
Stimulus
Signal Transduction
Stimulus
Perception(by receptor)
EffectorResponse
Effector…
EffectorEffector
External
Internal
Signal transduction step by step: Response
– such as changes in
cellular components
or production of new cellular components
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?
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
Bacteria and Plants Symbiosis
...
....
.
Bacteria far from root, 1nM Nod,
root grows towards bacteria
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
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.
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 Ca++ signals are transduced:Signatures vs. Switches
Signal transduction
– such as changes in
cellular components
or production of new cellular components