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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
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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?
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Is there anybody out there? Cells and organisms must monitor and respond to the environment.
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Stimulus Signal Transduction Stimulus Perception (by receptor) Effector Response Effector… Effector External Internal
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Signal transduction step by step: Perception
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Signal transduction step by step: Transduction
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Signal transduction step by step: Response – such as changes in cellular components or production of new cellular components
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Transduction can involve activation or inactivation of proteins.
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Cellular responses may involve changes in the expression of genes.
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Blood sugar levels as an example of cellular responses to the environment
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Why so many steps?
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Multiple steps allow for signal specificity. Different relay molecules lead to different responses
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Multiple steps allow for signal amplification: Calcium is a simple method of amplifying signals
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Calcium is a common effector. Cytoplasmic calcium levels are normally low.
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During signal transduction, calcium can be released into the cytoplasm: Perception
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During signal transduction, calcium can be released into the cytoplasm: Transduction
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During signal transduction, calcium can be released into the cytoplasm: Response
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During signal transduction, calcium can be released into the cytoplasm
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General model of Ca ++ signaling
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Multiple steps allow for signal amplification: Calcium is a simple method of amplifying signals
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Ca ++ is involved in many responses
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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?
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Everything has its place…
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Ikeda, Science 12 Oct 2001 Vol 294:318-319 Some Ca ++ channels have specific effectors associated with them: Micro-domains
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Root nodules: Nitrogen fixation
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Bacteria and Plants Symbiosis
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Signaling between bacteria and plants
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Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984 A biphasic Ca ++ response to Nod factor: 1nM Nod - toward nucleus 10nm Nod - away from nucleus 1nM Nod10nM Nod
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Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984 A biphasic Ca ++ response to Nod factor: 1nM Nod - toward nucleus 10nm Nod - away from nucleus 1nM Nod 10nM Nod 1nM Nod10nM Nod
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Everything has its place…
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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
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Photosynthesis: Plants can make sugar using energy from the sun, water from the ground, and CO 2 from the air.
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Stomata regulate gas exchange: CO 2 in, O 2 and water out H2OH2OH2OH2O
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Stomata closedopen
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Opening and closing of stomata
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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
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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
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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?
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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
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