Transcript Bio 226: Cell and Molecular Biology

Suggestions
1. Arabidopsis
2. Fast plant
3. Sorghum
4. Brachypodium distachyon
5. Amaranthus (C4 dicot)6. Quinoa
7. Kalanchoe
8. Venus fly traps
9. C3 vs C4 Atriplex
10. C3 vs C4 Flaveria
11. C3 vs C4 Panicum 12. M. crystallinum C3-CAM
13. P. afra C3-CAM
14 . P. oleracea C4-CAM
Options
1. Pick several plants
• C3, C4, CAM
• Long Day, Short day, Day Neutral
• Tropical, temperate, arctic
• ?????
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
WATER
• Plants' most important chemical
• most often limits productivity
•Gives cells shape
• Dissolves many chem: most biochem occurs in water
•Constantly lose water due to PS (1000 H2O/CO2)
Plant Water Uptake
Water is
drawn through
plants along
the SPAC,
relying on
adhesion &
cohesion
(&surface
tension) to
draw water
from the soil
into the air
Drawn through plant
by cohesion & adhesion
Surface tension & adhesion
in mesophyll creates force
that draws water through
the plant!
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
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
Water potential
Measuring water potential
Ys (osmotic potential) is “easy”
• Measure concentration of solution in equilibrium with
cells
Water potential
Measuring water potential
Ys (osmotic potential) is “easy”
• Measure concentration of solution in equilibrium with
cells
Yg (gravity potential) is easy: height above ground
• -0.01 Mpa/m
Water potential
Measuring water potential
Ys (osmotic potential) is “easy”
• Measure concentration of solution in equilibrium with
cells
Yg (gravity potential) is easy: height above ground
YP (pressure potential) is hard!
• Pressure bomb =
most common technique
Water potential
Measuring water potential
Ys (osmotic potential) is “easy”
• Measure concentration of solution in equilibrium with
cells
Yg (gravity potential) is easy: height above ground
YP (pressure potential) is hard!
• Pressure bomb =
most common technique
Others include pressure
transducers, xylem probes
Measuring water potential
YP (pressure potential) is hard!
• Pressure bomb =
most common technique
Others include pressure
transducers, xylem probes
Therefore disagree about H2O
transport in xylem
Water transport
Therefore disagree about H2O
transport in xylem
• Driving force = evaporation
in leaves (evapotranspiration)
• Continuous H2O column
from leaf to root draws up
replacement H2O from soil (SPAC)
Water transport
Driving force = evaporation
in leaves (evapotranspiration)
• Continuous H2O column
from leaf to root draws up
replacement H2O
• Exact mech controversial
Water transport
Driving force = evaporation in leaves (evapotranspiration)
• Continuous H2O column from leaf to root draws up
replacement H2O
• Exact mech controversial
Path starts at root hairs
Water transport
Path starts at root hairs
• Must take water from soil
Measuring water potential
Path starts at root hairs
• Must take water from soil
• Ease depends on availability
& how tightly it is bound
Measuring water potential
Path starts at root hairs
• Must take water from soil
• Ease depends on availability & how tightly it is bound
• Binding depends on particle size & chem
Measuring water potential
Must take water from soil
• Ease depends on availability & how tightly it is bound
• Binding depends on particle size & chem
• Availability depends on amount in soil pores
Measuring water potential
Availability depends on amount in soil pores
• Saturation: completely full
Measuring water potential
Availability depends on amount in soil pores
• Saturation: completely full
• Field capacity: amount left after gravity has drained
excess
Measuring water potential
Availability depends on amount in soil pores
• Saturation: completely full
• Field capacity: amount left after gravity has drained
excess
• Permanent wilting point: amount where soil water
potential is too negative for plants to take it up
Water movement in plants
Water enters via root hairs mainly through apoplast until
hits Casparian strip : hydrophobic barrier in cell walls of
endodermis
Water movement in plants
Water enters via root hairs mainly through apoplast until
hits Casparian strip : hydrophobic barrier in cell walls of
endodermis
Must enter
endodermal cell
Water Transport
Water enters via root hairs mainly through apoplast until
hits Casparian strip : hydrophobic barrier in cell walls of
endodermis
Must enter
endodermal cell
Why flooded
plants wilt!
Water Transport
Water enters via root hairs mainly through apoplast until
hits Casparian strip : hydrophobic barrier in cell walls of
endodermis
Must enter
endodermal cell
Why flooded
plants wilt!
Controls solutes
Water Transport
Must enter endodermal cell
Controls solutes
Passes water & nutrients to xylem
Water Transport
Passes water & nutrients to xylem
Ys of xylem makes root pressure
Water Transport
Passes water & nutrients to xylem
Ys of xylem makes root pressure
Causes guttation: pumping water into shoot
Water Transport
Passes water & nutrients to xylem
Ys of xylem makes root pressure
Causes guttation: pumping water into shoot
Most water enters near root tips
Water Transport
Most water enters near root tips
Xylem is dead! Pipes for moving water from root to shoot
Water Transport
Most water enters near root tips
Xylem is dead! Pipes for moving water from root to shoot
Most movement is bulk flow
Water Transport
Xylem is dead! Pipes for moving water from root to shoot
Most movement is bulk flow
• adhesion to cell wall helps
Water Transport
Xylem is dead! Pipes for moving water from root to shoot
Most movement is bulk flow
• adhesion to cell wall helps
•Especially if column is broken by
cavitation (forms embolisms)
Water Transport
Most movement is bulk flow
• adhesion to cell wall helps
•Especially if column broken by cavitation
In leaf water passes to mesophyll
Water Transport
Most movement is bulk flow
• adhesion to cell wall helps
•Especially if column broken by cavitation
In leaf water passes to mesophyll, then to air via stomates
Water Transport
In leaf water passes to mesophyll, then to air via stomates
Driving force = vapor pressure deficit (VPD)
• air dryness
Water Transport
In leaf water passes to mesophyll, then to air via stomates
Driving force = vapor pressure deficit (VPD)
• air dryness
•∆ H2O vapor pressure [H2O(g)]
& saturated H2O vapor pressure
Water Transport
In leaf water passes to mesophyll, then to air via stomates
Driving force = vapor pressure deficit (VPD)
• air dryness
•∆ H2O vapor pressure [H2O(g)]
& saturated H2O vapor pressure
• saturated H2O vapor pressure
varies with T, so RH depends on T
Water Transport
In leaf water passes to mesophyll, then to air via stomates
Driving force = vapor pressure deficit (VPD)
• air dryness
•∆ H2O vapor pressure [H2O(g)]
& saturated H2O vapor pressure
• saturated H2O vapor pressure
varies with T, so RH depends on T
• VPD is independent of T: says
how fast plants lose H2O at any T
Water Transport
In leaf water passes to mesophyll, then to air via stomates
Driving force = vapor pressure deficit (VPD)
• air dryness
Rate depends on pathway resistances
Water Transport
Rate depends on pathway resistances
• stomatal resistance
Water Transport
Rate depends on pathway resistances
• stomatal resistance
• Controlled by opening/closing
Water Transport
Rate depends on pathway resistances
• stomatal resistance
• boundary layer resistance
• Influenced by leaf shape & wind
Florigenic and antiflorigenic signaling pathways in Arabidopsis.
Matsoukas I G et al. Plant Cell Physiol 2012;53:1827-1842
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
• Age
Transition to Flowering
Can be affected by daylength (photoperiodic pathway)
• Mainly through CO protein stability
Transition to Flowering
Can be affected by daylength (photoperiodic pathway)
• Mainly through CO protein stability
• FKF1/GI bind CO & remove FT & CO inhibitor CDF
in afternoon (controlled by clock & enhanced by blue l)
Transition to Flowering
Can be affected by daylength (photoperiodic pathway)
• Mainly through CO protein stability
• FKF1/GI bind CO & remove FT & CO inhibitor CDF
in afternoon (controlled by clock & enhanced by blue l)
• FKF1/GI controlled
by circadian clock
Transition to Flowering
Can be affected by daylength
• Mainly through CO protein stability
• FKF1/GI bind CO & remove FT & CO inhibitor CDF
in afternoon (controlled by clock & enhanced by blue l)
• FKF1/GI controlled
by circadian clock
• PHYA & CRY
also stabilize CO @
end of day
Transition to Flowering
Can be affected by daylength
Can be affected by T
• FLC blocks flowering in fall; after 20 days near 0˚C
plants make COLDAIR ncRNA
FLC blocks flowering in fall; after 20 days near 0˚C plants
make COLDAIR ncRNA: Targets Polycomb Repressor
Complex 2 to
FLC locus &
makes
H3K27me3 ->
silences gene
Transition to Flowering
Can be affected by daylength
Can be affected by T
• FLC blocks flowering in fall; after 20 days near 0˚C
plants make COLDAIR ncRNA ->PRC2 silences FLC
• Can then flower
next spring
Transition to Flowering
Can be affected by daylength
Can be affected by T
• FLC blocks flowering in fall; after 20 days near 0˚C
plants make COLDAIR ncRNA ->PRC2 silences FLC
• Can then flower
next spring
• PIF4 activates
flowering @ high T
by inducing FT mRNA
(ind of daylength)
Transition to Flowering
Can be affected by daylength
Can be affected by T
Can be affected by gibberellins (GA)
Gibberellins
Discovered by studying "foolish seedling" disease in rice
• Kurosawa (1926): fungal filtrate causes these effects
• Yabuta (1935): purified gibberellins from filtrates of
Gibberella fujikuroi cultures
• Discovered in
plants in 1950s
Gibberellins
Discovered in plants in 1950s
• "rescued" some dwarf corn & pea mutants
• Made rosette plants bolt
Gibberellins
Discovered in plants in 1950s
• "rescued" some dwarf corn & pea mutants
• Made rosette plants bolt
• Trigger adulthood in
ivy & conifers
•
•
•
•
•
Gibberellins
"rescued" some dwarf corn & pea mutants
Made rosette plants bolt
Trigger adulthood in ivy & conifers
Induce growth of seedless fruit
Promote seed germination
Gibberellins
• "rescued" some dwarf corn
& pea mutants
• Made rosette plants bolt
• Trigger adulthood in ivy
& conifers
• Promote seed germination
• >136 gibberellins (based on
structure)!
Gibberellins
>136 gibberellins (based on
structure)!
• Most plants have >10
• Activity varies dramatically!
Gibberellins
>136 gibberellins (based on
structure)!
• Most plants have >10
• Activity varies dramatically!
• Most are precursors or
degradation products
• GAs 1, 3 & 4 are most bioactive
Gibberellin signaling
Used mutants to learn about GA signaling
•Many are involved in GA synthesis
•Varies during development
•Others hit GA signaling
•Gid = GA insensitive
• encode GA receptors
•Sly = E3 receptors
•DELLA (eg rga) =
repressors of GA signaling
Gibberellins
GAs 1, 3 & 4 are most bioactive
Act by triggering degradation
of DELLA repressors
Gibberellins
GAs 1, 3 & 4 are most bioactive
Made at many locations in plant
Act by triggering degradation
of DELLA repressors
w/o GA DELLA binds & blocks activator (GRAS)
Gibberellins
Act by triggering degradation of DELLA repressors
w/o GA DELLA binds & blocks activator
bioactive GA binds GID1; GA-GID1 binds DELLA & marks for
destruction
Gibberellins
Act by triggering degradation of DELLA repressors
w/o GA DELLA binds & blocks activator
bioactive GA binds GID1; GA-GID1 binds DELLA & marks for
destruction
GA early genes are
transcribed, start
GA responses
Transition to Flowering
Can be affected by gibberellins (GA)
DELLA bind microRNA156 (miR156)-targeted SPL
transcription factors, which promote flowering by
activating miR172 and MADS box genes
Transition to Flowering
Can be affected by gibberellins (GA)
DELLA bind microRNA156 (miR156)-targeted SPL
transcription factors, which promote flowering by
activating miR172 and MADS box genes
GA triggers DELLA
deg releasing SPL
Transition to Flowering
Can be affected by age (autonomous pathway)
In young plants, SPL synthesis is blocked by high levels of
miRNA156 : delays juvenile -> adult (OE delays it
more)
Transition to Flowering
Can be affected by age (autonomous pathway)
In young plants, SPL synthesis is blocked by high levels of
miR156 : delays juvenile -> adult
miR156 levels decay with age independently of other cues
->let SPL act
Transition to Flowering
Can be affected by age (autonomous pathway)
In young plants, SPL synthesis is blocked by high levels of
miR156 : delays juvenile -> adult
miR156 levels decay with age independently of other cues
->let SPL act
Tomato terminating
flower mutants
(tmf) flower early :
TMF coordinates
transition to
flowering
Transition to Flowering
Can be affected by nutrition
Pi deprivation induces miR399
Travels in phloem to repress PHO2, a neg regulator of Pi
uptake
Transition to Flowering
Can be affected by nutrition
Pi deprivation induces miR399
Travels in phloem to repress PHO2, a neg regulator of Pi
uptake
miR399 enhances
TSF expression
Transition to Flowering
Can be affected by nutrition
Pi deprivation induces miR399
Travels in phloem to repress PHO2, a neg regulator of Pi
uptake
miR399 enhances
TSF expression
Sucrose enhances
miR399 expression
(also many other genes)
Transition to Flowering
Can be affected by nutrition
Pi deprivation induces miR399
Travels in phloem to repress PHO2, a neg regulator of Pi
uptake
miR399 enhances
TSF expression
Sucrose enhances
miR399 expression
(also many other genes)
miR399 is Temp S!
http://www3.syngenta.com/global/e-licensing/en/elicensing/Catalog/Pages/Chemicallyinducedsucrosemetabolismtocontrolplantflowering.aspx