Download Jan 25

Plan C
We will pick a problem in plant biology and see where it takes us.
1. Phytoremediation II
2. Plant products
3.
Biofuels VIII
4. Climate/CO2 change III
5. Stress responses/stress avoidance I
6. Improving food production
7. Biotechnology
8. Plant movements III
9. Plant signaling (including neurobiology)VI
10. Flowering?
11. Regeneration? Seed germination?
12. Bioluminescence II
endosymbionts
• derived by division of preexisting organelles
• no vesicle transport
•Proteins & lipids are not glycosylated
endosymbionts
1) Peroxisomes (microbodies)
2) Mitochondria
Mitochondria
Fn : cellular respiration
-> oxidizing food & supplying energy to cell
Also make important biochems & help recycle PR prods
• Have extra oxidases: burn off excess NADH or NADPH?
Mitochondria
Fn : cellular respiration
-> oxidize food & supply energy to cell
Also make important biochems & help
recycle PR prods
• Have extra oxidases: burn off excess
NADH or NADPH?
• Do lots of extra biochemistry
endosymbionts
1) Peroxisomes
2) Mitochondria
3) Plastids
Plastids
Chloroplasts do photosynthesis
Amyloplasts store starch
Chromoplasts store pigments
Leucoplasts are found in roots
Chloroplasts
Bounded by 2 membranes
1) outer envelope
2) inner envelope
Chloroplasts
Interior = stroma
Contains thylakoids
• membranes where light
rxns of photosynthesis occur
•mainly galactolipids
Chloroplasts
Interior = stroma
Contains thylakoids
• membranes where light rxns of photosynthesis occur
•mainly galactolipids
Contain DNA, RNA, ribosomes
Chloroplasts
Contain DNA, RNA, ribosomes
120,000-160,000 bp, ~ 100 genes
Chloroplasts
Contain DNA, RNA, ribosomes
120,000-160,000 bp, ~ 100 genes
Closest relatives = cyanobacteria
Chloroplasts
Contain DNA, RNA, ribosomes
120,000-160,000 bp, ~ 100 genes
Closest relatives = cyanobacteria
Divide by fission
Chloroplasts
Contain DNA, RNA, ribosomes
120,000-160,000 bp, ~ 100 genes
Closest relatives = cyanobacteria
Divide by fission
Fns: Photosynthesis
Chloroplasts
Fns: Photosynthesis & starch synth
Photoassimilation of N & S
Chloroplasts
Fns: Photosynthesis & starch synth
Photoassimilation of N & S
Fatty acid & some lipid synth
Chloroplasts
Fns: Photosynthesis & starch synth
Photoassimilation of N & S
Fatty acid & some lipid synth
Synth of ABA, GA, many other biochem
Chloroplasts & Mitochondria
Contain eubacterial DNA, RNA, ribosomes
Inner membranes have bacterial lipids
Divide by fission
Provide best support for endosymbiosis
Endosymbiosis theory (Margulis)
Archaebacteria ate eubacteria & converted them to
symbionts
Endosymbiosis theory (Margulis)
Archaebacteria ate
eubacteria &
converted them
to symbionts
Endosymbiosis theory (Margulis)
Archaebacteria ate
eubacteria &
converted them
to symbionts
cytoskeleton
network of proteins which give cells their shape
also responsible for shape of plant cells because guide
cell wall formation
left intact by detergents that extract rest of cell
Cytoskeleton
Actin fibers (microfilaments)
~7 nm diameter
Form 2 chains of polar actin subunits arranged in a double
helix
Actin fibers
polar subunits arranged in a double helix
• Add to + end
• Fall off - end
• Fn = movement
Actin fibers
Very conserved in evolution
Fn = motility
Often with myosin
Actin fibers
Very conserved in evolution
Fn = motility
Often with myosin: responsible for cytoplasmic streaming
Actin fibers
Very conserved in evolution
Fn = motility
Often with myosin: responsible for cytoplasmic streaming,
Pollen tube growth & movement through plasmodesmata
Actin fibers
Often with myosin: responsible for cytoplasmic streaming,
Pollen tube growth & movement through plasmodesmata
Intermediate filaments
Protein fibers 8-12 nm dia (between MFs & MTs)
form similar looking filaments
Conserved central, rod-shaped
-helical domain
Intermediate filaments
2 monomers form dimers with parallel subunits
Dimers form
tetramers
aligned in
opposite
orientations
& staggered
Intermediate filaments
2 monomers form dimers with parallel subunits
Dimers form
tetramers
Tetramers
form IF
Intermediate filaments
2 monomers form dimers with parallel subunits
Dimers form
tetramers
Tetramers
form IF
Plants have several
keratins: fn unclear
Intermediate filaments
2 monomers form dimers with parallel subunits
Dimers form tetramers
Tetramers form IF
Plants have several keratins: fn unclear
No nuclear lamins!
Have analogs that form similar structures
Microtubules
Hollow, cylindrical; found in most eukaryotes
outer diameter - 24 nm
wall thickness - ~ 5 nm
Made of 13 longitudinal rows
of protofilaments
Microtubules
Made of a b tubulin subunits
polymerize to form protofilaments (PF)
PF form sheets
Sheets form
microtubules
Microtubules
Protofilaments are polar
a-tubulin @ - end
b-tubulin @ + end
all in single MT have same
polarity
Microtubules
In constant flux
polymerizing & depolymerizing
Add to b (+)
Fall off a (-)
Microtubules
Control growth by controlling
rates of assembly & disassembly
because these are distinct processes
can be controlled independently!
Colchicine makes MTs disassemble
Taxol prevents disassembly
Microtubules
Control growth by controlling rates of assembly &
disassembly
Are constantly rearranging inside plant cells!
Microtubules
Control growth by controlling rates of assembly &
disassembly
Are constantly rearranging inside plant cells!
• during mitosis & cytokinesis
Microtubules
Control growth by controlling rates of assembly &
disassembly
Are constantly rearranging inside plant cells!
• during mitosis & cytokinesis
• Guide formation of cell plate & of walls in interphase
µT Assembly
µTs always emerge from Microtubule-Organizing Centers
(MTOC)
µT Assembly
µTs always emerge from Microtubule-Organizing Centers
(MTOC) patches of material at outer nuclear envelope
Microtubules
MAPs (Microtubule Associated Proteins) may:
• stabilize tubules
• alter rates of
assembly/disassembly
• crosslink adjacent
tubules
• link cargo
2 classes of molecular motors
1) Kinesins move cargo to µT plus end
2) Dyneins move cargo to minus end
“Walk” hand-over-hand towards chosen end
µT functions
1) Give cells shape by guiding cellulose synth
µT functions
1) Give cells shape by guiding cellulose synth
2) Anchor organelles
µT functions
1) Give cells shape by guiding cellulose synth
2) Anchor organelles
3) Intracellular motility