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

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