Homework 1 is posted and due 920 Bonus
• 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 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: • • • 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
1 n. M Nod Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976– 984 10 n. M Nod A biphasic Ca++ response to Nod factor: 1 n. M Nod - toward nucleus 10 nm Nod - away from nucleus
1 n. M Nod 10 n. M Nod A biphasic Ca++ response to Nod factor: 1 n. M Nod - toward nucleus 10 nm 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 CO 2 from the air.
Stomata regulate gas exchange: CO 2 in, O 2 and water out H 2 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. det 3 and gca 2: mutants that fail to close stomata following treatment Fig 5. Sanders et al. , The Plant Cell, S 401–S 417, 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
- Slides: 43