Plan C

1.Pick a problem2.Pick some plants to study3.Design some experiments4.See where they lead us

Endomembrane systemOrganelles derived from the ER1) ER2) Golgi3) Vacuoles 4) PlasmaMembrane5) Nuclear Envelope6) Endosomes7) Oleosomes

VACUOLESVacuoles are subdivided: lytic vacuoles are distinctfrom storage vacuoles!

Endomembrane SystemOleosomes: oil storage bodies derived from SERSurrounded by lipid monolayer!

• filled with lipids: no internal hydrophobic effect!

endosymbionts• derived by division of preexisting organelles• no vesicle transport•Proteins & lipids are not glycosylated

endosymbionts•derived by division of preexisting organelles• little exchange of membranes with other organelles1) Peroxisomes (microbodies)

Peroxisomes (microbodies)1 membrane

Peroxisomes (microbodies)found in (nearly) all eukaryotes1 membraneFn:

1) destroy H2O2, other O2-related poisons

PeroxisomesFn:

1. destroy H2O2, other O2-related poisons2. change fat to CH2O (glyoxysomes)

PeroxisomesFns:

1. destroy H2O2, other O2-related poisons2. change fat to CH2O (glyoxysomes)• Detoxify & recycle photorespiration products

PeroxisomesFn:

• destroy H2O2, other O2-related poisons• change fat to CH2O (glyoxysomes)• Detoxify & recycle photorespiration products• Destroy EtOH (made in anaerobic roots)

PeroxisomesER can make peroxisomes under special circumstances!e.g. peroxisome-less mutants can restore peroxisomes when

the wild-type gene is restored

endosymbionts1) Peroxisomes (microbodies)2) Mitochondria

MitochondriaBounded by 2 membranes

Mitochondria2 membranesSmooth OM

Mitochondria2 membranesSmooth OMIM folds into cristae

Mitochondria-> 4 compartments

1) OM2) intermembrane space3) IM4) matrix

Mitochondria matrix contains DNA, RNA and ribosomes

Mitochondria matrix contains DNA, RNA and ribosomesGenomes vary from 100,000 to 2,500,000 bp, but only 40-43 genes

Mitochondriamatrix contains DNA, RNA and ribosomesGenomes vary from 100,000 to 2,500,000 bp, but only 40-43 genesReproduce by fission

Mitochondriamatrix contains DNA, RNA and ribosomesGenomes vary from 100,000 to 2,500,000 bp, but only 40-43 genesReproduce by fissionIM is 25% cardiolipin, a bacterial phospholipid

MitochondriaGenomes vary from 100,000 to 2,500,000 bp, but only 40-43 genesReproduce by fissionIM is 25% cardiolipin, a bacterial phospholipidGenes most related to Rhodobacteria

MitochondriaFn : cellular respiration -> oxidizing food & supplying energy to cellAlso make many important biochemicals

MitochondriaFn : cellular respiration -> oxidizing food & supplying energy to cellAlso make important biochemicals & help recycle PR products

endosymbionts1) Peroxisomes2) Mitochondria 3) Plastids

PlastidsChloroplasts do photosynthesisAmyloplasts store starchChromoplasts store pigmentsLeucoplasts are found in roots

ChloroplastsBounded by 2 membranes

1) outer envelope 2) inner envelope

ChloroplastsInterior = stromaContains thylakoids• membranes where light rxns of photosynthesis occur•mainly galactolipids

ChloroplastsInterior = stromaContains thylakoids• membranes where light rxns of photosynthesis occur•mainly galactolipidsContain DNA, RNA, ribosomes

ChloroplastsContain DNA, RNA, ribosomes120,000-160,000 bp, ~ 100 genes

ChloroplastsContain DNA, RNA, ribosomes120,000-160,000 bp, ~ 100 genesClosest relatives = cyanobacteria

ChloroplastsContain DNA, RNA, ribosomes120,000-160,000 bp, ~ 100 genesClosest relatives = cyanobacteriaDivide by fission

ChloroplastsContain DNA, RNA, ribosomes120,000-160,000 bp, ~ 100 genesClosest relatives = cyanobacteriaDivide by fissionFns: Photosynthesis

ChloroplastsFns: Photosynthesis & starch synthPhotoassimilation of N & S

ChloroplastsFns: Photosynthesis & starch synthPhotoassimilation of N & SFatty acid & some lipid synth

ChloroplastsFns: Photosynthesis & starch synthPhotoassimilation of N & SFatty acid & some lipid synthSynth of ABA, GA, many other biochem

Chloroplasts & MitochondriaContain eubacterial DNA, RNA, ribosomesInner membranes have bacterial lipidsDivide by fissionProvide best support for endosymbiosis

Endosymbiosis theory (Margulis)Archaebacteria ate eubacteria & converted them to symbionts

Endosymbiosis theory (Margulis)Archaebacteria ate eubacteria & converted themto 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 formationleft intact by detergents that extract rest of cell

CytoskeletonActin fibers (microfilaments)~7 nm diameterForm 2 chains of polar actin subunits arranged in a double helix

Actin fiberspolar subunits arranged in a double helix• Add to + end• Fall off - end• Fn = movement

Actin fibersVery conserved in evolutionFn = motilityOften with myosin

Actin fibersVery conserved in evolutionFn = motilityOften with myosin: responsible for cytoplasmic streaming

Actin fibersVery conserved in evolutionFn = motilityOften with myosin: responsible for cytoplasmic streaming,Pollen tube growth & movement through plasmodesmata

Actin fibersOften 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 filaments2 monomers form dimers with parallel subunitsDimers form tetramersaligned in opposite orientations& staggered

Intermediate filaments2 monomers form dimers with parallel subunitsDimers form tetramersTetramers form IF

Intermediate filaments2 monomers form dimers with parallel subunitsDimers form tetramersTetramers form IFPlants have several:Fn unclear

MicrotubulesHollow, cylindrical; found in most eukaryotes

outer diameter - 24 nmwall thickness - ~ 5 nmMade of 13 longitudinal rows of protofilaments

MicrotubulesMade of tubulin subunits polymerize to form protofilaments (PF)PF form sheetsSheets form microtubules

MicrotubulesProtofilaments are polar -tubulin @ - end-tubulin @ + endall in single MT have same polarity

MicrotubulesIn constant fluxpolymerizing & depolymerizingAdd to (+)Fall off (-)

MicrotubulesControl growth by controllingrates of assembly & disassembly

because these are distinct processes can be controlled independently!

Colchicine makes MTs disassemble

Taxol prevents disassembly

MicrotubulesControl growth by controlling rates of assembly & disassemblyAre constantly rearranging inside plant cells!

MicrotubulesControl growth by controlling rates of assembly & disassemblyAre constantly rearranging inside plant cells!

• during mitosis & cytokinesis

MicrotubulesControl growth by controlling rates of assembly & disassemblyAre 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

MicrotubulesMAPs (Microtubule Associated Proteins) may:

• stabilize tubules• alter rates of assembly/disassembly• crosslink adjacent tubules • link cargo

2 classes of molecular motors1) Kinesins move cargo to µT plus end2) Dyneins move cargo to minus end “Walk” hand-over-hand towards chosen end

µT functions1) Give cells shape by guiding cellulose synth

µT functions1) Give cells shape by guiding cellulose synth2) Anchor organelles

µT functions1) Give cells shape by guiding cellulose synth2) Anchor organelles3) Intracellular motility