Transcript Bio 226: Cell and Molecular Biology

Game plan
We will study effects of elevated CO2 and temperature on
flowering time and see where it takes us.
1. Learn more about how plants choose when to flower
Game plan
We will study effects of elevated CO2 and temperature on
flowering time and see where it takes us.
1. Learn more about how plants choose when to flower
•Environmental influences on flowering
Game plan
We will study effects of elevated CO2 and temperature on
flowering time and see where it takes us.
1. Learn more about how plants choose when to flower
•Environmental influences on flowering
2. Pick some plants to study
Game plan
We will study effects of elevated CO2 and temperature on
flowering time and see where it takes us.
1. Learn more about how plants choose when to flower
•Environmental influences on flowering
2. Pick some plants to study
3. Get them growing
Game plan
We will study effects of elevated CO2 and temperature on
flowering time and see where it takes us.
1. Learn more about how plants choose when to flower
•Environmental influences on flowering
2. Pick some plants to study
3. Get them growing
4. Design some experiments for other things to test before
they start flowering
1.Arabidopsis
3. Sorghum
5. Amaranthus
7. Kalanchoe
Game plan
Suggestions
2. Fast plant
4. Brachypodium distachyon
6. Quinoa
8. Venus fly traps
Options
1.Pick several plants
1.Arabidopsis
3. Sorghum
5. Amaranthus
7. Kalanchoe
Game plan
Suggestions
2. Fast plant
4. Brachypodium distachyon
6. Quinoa
8. Venus fly traps
Options
1.Pick several plants
• C3, C4, CAM
1.Arabidopsis
3. Sorghum
5. Amaranthus
7. Kalanchoe
Game plan
Suggestions
2. Fast plant
4. Brachypodium distachyon
6. Quinoa
8. Venus fly traps
Options
1.Pick several plants
• C3, C4, CAM
• Long Day, short day, Day neutral
1.Arabidopsis
3. Sorghum
5. Amaranthus
7. Kalanchoe
Game plan
Suggestions
2. Fast plant
4. Brachypodium distachyon
6. Quinoa
8. Venus fly traps
Options
1.Pick several plants
• C3, C4, CAM
• Long Day, short day, Day neutral
• Tropical, temperate, arctic
1. Arabidopsis
3. Sorghum
5. Amaranthus
7. Kalanchoe
Game plan
Suggestions
2. Fast plant
4. Brachypodium distachyon
6. Quinoa
8. Venus fly traps
Options
1. Pick several plants
• C3, C4, CAM
• Long Day, short day, Day neutral
• Tropical, temperate, arctic
• ?????
1. Arabidopsis
3. Sorghum
5. Amaranthus
7. Kalanchoe
Game plan
Suggestions
2. Fast plant
4. Brachypodium distachyon
6. Quinoa
8. Venus fly traps
Options
1. Pick several plants
• C3, C4, CAM
• Long Day, short day, Day neutral
• Tropical, temperate, arctic
• ?????
2. Pick one plant
• Study many conditions
Options
1. Pick several plants
• C3, C4, CAM
• Long Day, short day, Day neutral
• Tropical, temperate, arctic
• ?????
2. Pick one plant
• Study many conditions
• Study many variants/mutants
• ?????
Grading?
Combination of papers, presentations & lab reports
• 4 lab reports @ 2.5 points each
• 5 assignments @ 2 points each
• Presentation on global change and plants: 5 points
• Research proposal: 10 points
• Final presentation: 15 points
• Poster: 10 points
• Draft report 10 points
• Final report: 30 points
Assignment 1
1.Pick a plant that might be worth studying
•Try to convince the group in 5-10 minutes why yours
is best: i.e., what is known/what isn’t known
Plant Growth & Development
Occurs in 3 stages
1. Embryogenesis
From fertilization to seed
2. Vegetative growth
Juvenile stage
From seed germination to adult
"phase change" marks transition
3. Reproductive development
Start making flowers, can
reproduce sexually
Transition to Adult Phase
Juveniles & adults are very different!
Transition to Flowering
Adults are competent to flower, but need correct signals
Very complex process!
Can be affected by:
• Daylength
• Temperature (especially cold!)
• Water stress
• Nutrition
• Hormones
Early Studies
Julius Sachs (1865) first proposed florigen
Garner and Allard (1920) discovered photoperiodism
Maryland Mammoth tobacco flowers in the S but not in N
Knott (1934) day length is perceived by the leaves
Early Studies
Knott (1934) day length is perceived by the leaves
• Flowers are formed at SAM!
• Florigen moves from leaves
to SAM
• Is graft-transmissable!
• Moves in phloem
Complications
Some plants are qualitative (must have correct daylength),
others are quantitative (correct days speed flowering)
Four pathways control flowering:
1. Photoperiod
• PHY only
• PHY + CRY
2. Vernalization: requires cold period
3. gibberellin (GA)
4. Autonomous
Complications
Florigen is “universal”: transmitted from LDP to SDP and
vice-versa via grafts
Solved by identifying genes that control flowering time
Genes controlling flowering
Florigen is “universal”: transmitted from LDP to SDP and
vice-versa via grafts
Solved by identifying genes that control flowering time
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
Genes controlling flowering
Florigen is “universal”: transmitted from LDP to SDP and
vice-versa via grafts
Solved by identifying genes that control flowering time
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
• CO mRNA is expressed in leaf but not SAM &
increases in LD
Genes controlling flowering
Florigen is “universal”: transmitted from LDP to SDP and
vice-versa via grafts
Solved by identifying genes that control flowering time
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
• CO mRNA is expressed in leaf but not SAM &
increases in LD
• CO encodes a ZN-finger transcription factor
(TF) that induces expression of FLOWERING
LOCUS T (FT)
Genes controlling flowering
Florigen is “universal”: transmitted from LDP to SDP and
vice-versa via grafts
Solved by identifying genes that control flowering time
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
• CO mRNA is expressed in leaf but not SAM &
increases in LD
• CO encodes a ZN-finger TF that induces
expression of FLOWERING LOCUS T (FT)
2. FLOWERING LOCUS T (FT): a strong promoter
of flowering
Genes controlling flowering
Florigen is “universal”: transmitted from LDP to SDP and
vice-versa via grafts
Solved by identifying genes that control flowering time
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
• CO mRNA is expressed in leaf but not SAM &
increases in LD
• CO encodes a ZN-finger TF that induces
expression of FLOWERING LOCUS T (FT)
2. FLOWERING LOCUS T (FT): a strong promoter
of flowering: encodes a RAF kinase inhibitor protein
Genes controlling flowering
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
2. FLOWERING LOCUS T (FT): a strong promoter of
flowering: encodes a RAF kinase inhibitor protein
3. FLOWERING LOCUS C (FLC): a MADS-box gene
strongly represses flowering
Genes controlling flowering
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
2. FLOWERING LOCUS T (FT): a strong promoter of
flowering: encodes a RAF kinase inhibitor protein
3. FLOWERING LOCUS C (FLC): a MADS-box gene
strongly represses flowering
• Highly expressed in non-vernalized tissues
Genes controlling flowering
1. CONSTANS (CO): co mutants are day-length
insensitive & flower late
2. FLOWERING LOCUS T (FT): a strong promoter of
flowering: encodes a RAF kinase inhibitor protein
3. FLOWERING LOCUS C (FLC): a MADS-box gene
strongly represses flowering
• Highly expressed in non-vernalized tissues
• Turned off by vernalization due to chromatin mod
1.
2.
3.
4.
Genes controlling flowering
CONSTANS (CO): co mutants are day-length
insensitive & flower late
FLOWERING LOCUS T (FT): a strong promoter of
flowering: encodes a RAF kinase inhibitor protein
FLOWERING LOCUS C (FLC): a MADS-box gene
strongly represses flowering
• Highly expressed in non-vernalized tissues
• Turned off by vernalization due to chromatin mod
SUPPRESSOR OF CONSTANS 1 (SOC1): a MADSBOX TF that activates genes for floral development.
Transition to flowering
Upon induction, CO activates transcription of FT in leaves
FT protein moves from leaves to shoot apex in phloem!
Transition to flowering
Upon induction, CO activates transcription of FT in leaves
FT protein moves from leaves to shoot apex in phloem!
In SAM combines with FD to activate SOC1 & AP1
Transition to flowering
Upon induction, CO activates transcription of FT
FT protein moves from leaves to shoot apex in phloem!
In SAM combines with FD to activate SOC1 &AP1
These activate LFY &
Flower genes
Transition to flowering
Upon induction, CO activates transcription of FT
FT protein moves from leaves to shoot apex in phloem!
In SAM combines with FD to activate SOC1 &AP1
These activate LFY &
Flower genes
Other signals converge
On SOC1, either
Directly or via FLC
SDP
Rice homolog to CO is Hd1
Inhibits expression of Hd3a
(the FT homolog)
SDP
Rice homolog to CO is Hd1
Inhibits expression of Hd3a
(the FT homolog)
Induced by long days
SDP
Rice homolog to CO is Hd1
Inhibits expression of Hd3a
(the FT homolog)
Induced by long days
Only make Hd3a protein
under short days
Transition to flowering
Eventually start flowering
• Are now adults!
• Time needed varies from days to years.
• Shoot apical meristem now starts making new organ:
flowers, with many new structures & cell types
WATER
• Plants' most important chemical
• most often limits productivity
WATER
• Plants' most important chemical
• most often limits productivity
• Often >90%% of a plant cell’s weight
WATER
• Plants' most important chemical
• most often limits productivity
• Often >90%% of a plant cell’s weight
• Gives cells shape
WATER
• Plants' most important chemical
• most often limits productivity
• Often >90%% of a plant cell’s weight
• Gives cells shape
• Dissolves many chem
WATER
• Dissolves many chem
• most biochem occurs in water
• Source of e- for PS
WATER
• most biochem occurs in water
• Source of e- for PS
• Constantly lose water due to PS (1000 H2O/CO2)
WATER
• most biochem occurs in water
• Source of e- for PS
• Constantly lose water due to PS
• Water transport is crucial!
WATER
• Water transport is crucial!
• SPAC= Soil Plant Air Continuum
• moves from soil->plant->air
WATER
Formula = H2O
Formula weight = 18 daltons
Structure = tetrahedron, bond angle 104.5˚
WATER
Structure = tetrahedron, bond angle 104.5˚
polar :O is more attractive to electrons than H
+ on H
- on O
Water
Polarity is reason for water’s properties
water forms H-bonds with polar molecules
Water
Polarity is reason for water’s properties
water forms H-bonds with polar molecules
Hydrophilic = polar molecules
Hydrophobic = non-polar molecules
Properties of water
1) Cohesion = water H-bonded to water
-> reason for surface tension
Properties of water
1) Cohesion = water H-bonded to water
-> reason for surface tension
-> why water can be drawn from roots to leaves
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
• Cohesion and adhesion are crucial for water
movement in plants!
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
• Cohesion and adhesion are crucial for water
movement in plants!
• Surface tension & adhesion in mesophyll creates
force that draws water through the plant!
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
• absorb heat when break H-bonds: cools leaves
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
• absorb heat when break H-bonds
• Release heat when form H-bonds
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
4) Ice floats
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
4) Ice floats
5) Universal solvent
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
4) Ice floats
5) Universal solvent
•Take up & transport
nutrients dissolved in
water
Properties of water
5) “Universal” solvent
•Take up & transport nutrients dissolved in water
•Transport organics dissolved in water
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
4) Ice floats
5) Universal solvent
6) Hydrophobic bonds
Properties of water
1) Cohesion = water H-bonded to water
2) Adhesion = water H-bonded to something else
3) high specific heat
4) Ice floats
5) Universal solvent
6) Hydrophobic bonds
7) Water ionizes
pH
[H+] = acidity of a solution
pH = convenient way
to measure acidity
pH = - log10 [H+]
pH 7 is neutral:
[H+] = [OH-]
-> at pH 7 [H+]
= 10-7 moles/l
pH
Plants vary pH to control many processes!
Water movement
Diffusion: movement of single molecules down ∆[ ] due to
random motion until [ ] is even
•Driving force?
Water movement
Diffusion: movement of single molecules down ∆[ ] due to
random motion until [ ] is even
• Driving force: lowers free energy
•∆G = ∆H- T∆S
Water movement
Diffusion: movement of single molecules down ∆[ ] due to
random motion until [ ] is even
Bulk Flow: movement of groups of
molecules down a pressure gradient
Water movement
Diffusion: movement of single molecules down ∆[ ] due to
random motion until [ ] is even
Bulk Flow: movement of groups of
molecules down a pressure gradient
• Independent of ∆ [ ] !
Water movement
Diffusion: movement of single molecules down ∆[] due to
random motion until [ ] is even
Bulk Flow: movement of groups of molecules down a
pressure gradient
•Independent of ∆[ ] !
•How water moves through xylem
Water movement
Diffusion: movement of single molecules down [] due to
random motion until [ ] is even
Bulk Flow: movement of groups of molecules down a
pressure gradient
•Independent of ∆ [ ] !
•How water moves through xylem
•How water moves through soil and apoplast
Water movement
Bulk Flow: movement of groups of molecules down a
pressure gradient
•Independent of ∆ [ ] !
•How water moves through xylem
•Main way water moves through soil and apoplast
•Very sensitive to radius of vessel: increases as r4
Water movement
Diffusion: movement of single molecules down ∆[] due to
random motion until [ ] is even
Bulk Flow: movement of groups of molecules down a
pressure gradient
•Independent of ∆[ ] !
•How water moves through xylem
•Main way water moves through soil and apoplast
•Very sensitive to radius of vessel: increases as r4
Osmosis: depends on bulk flow and diffusion!
Water movement
Osmosis: depends on bulk flow and diffusion!
water crosses membranes but other solutes do not
water tries to even its [ ] on each side
Water movement
Osmosis: depends on bulk flow and diffusion!
water crosses membranes but other solutes do not
water tries to even its [ ] on each side
other solutes can’t: result is net influx of water
Water movement
Osmosis: depends on bulk flow and diffusion!
•Moves through aquaporins, so rate depends on
pressure and [ ] gradients!
Water movement
Osmosis: depends on bulk flow and diffusion!
•Moves through aquaporins, so rate depends on
pressure and [ ] gradients!
• Driving force = water's free energy (J/m3 = MPa)
Water potential
Driving force = water's free energy
= water potential Yw
• Important for many aspects of
plant physiology
Water potential
Driving force = water's free energy = water potential Yw
Water moves to lower its potential
Water potential
Driving force = water's free energy = water potential Yw
Water moves to lower its potential
Water potential
Driving force = water's free energy = water potential Yw
Water moves to lower its potential
Depends on:
1. [H2O]: Ys (osmotic potential)
Water potential
Water moves to lower its potential
Depends on:
1. [H2O]: Ys (osmotic potential)
2. Pressure : Yp
• Turgor pressure inside cells
Water potential
Water moves to lower its potential
Depends on:
1. [H2O]: Ys (osmotic potential)
2. Pressure : Yp
• Turgor pressure inside cells
• Negative pressure in xylem!
Water potential
Water moves to lower its potential
Depends on:
1. [H2O]: Ys (osmotic potential)
2. Pressure Yp
3. Gravity Yg
Yw = Ys +Yp + Yg
Water potential
Water moves to lower its potential
Depends on:
1. [H2O]: Ys (osmotic potential)
2. Pressure Yp
3. Gravity Yg
Yw = Ys +Yp + Yg
Yw of pure water at sea level
& 1 atm = 0 MPA
Yw = Ys +Yp + Yg
Water potential
Yw of pure water at sea level & 1 atm = 0 MPA
Ys (osmotic potential) is always negative
Yw = Ys +Yp + Yg
Water potential
Yw of pure water at sea level & 1 atm = 0 MPA
Ys (osmotic potential) is always negative
• If increase [solutes] water will move in
Yw = Ys +Yp + Yg
Water potential
Yw of pure water at sea level & 1 atm = 0 MPA
Ys (osmotic potential) is always negative
• If increase [solutes] water will move in
Yp (pressure potential) can be positive or negative
Yw = Ys +Yp + Yg
Water potential
Yw of pure water at sea level & 1 atm = 0 MPA
Ys (osmotic potential) is always negative
• If increase [solutes] water will move in
Yp (pressure potential) can be positive or negative
• Usually positive in cells to counteract Ys
Water potential
Yp (pressure potential) can be positive or negative
• Usually positive in cells to counteract Ys
• Helps plants stay same size despite daily fluctuations in
Yw
Water potential
Yw = Ys +Yp + Yg
Yp (pressure potential) can be positive or negative
• Usually positive in cells to counteract Ys
• Helps plants stay same size
despite daily fluctuations in Yw
• Yp in xylem is negative, draws
water upwards
Water potential
Yw = Ys +Yp + Yg
Yp (pressure potential) can be positive or negative
• Usually positive in cells to counteract Ys
• Helps plants stay same size
despite daily fluctuations in Yw
• Yp in xylem is negative, draws
water upwards
Yg can usually be ignored, but
important for tall trees