Plan C We will pick a problem in plant biology and see where it takes us. Phytoremediation II Plant products Biofuels VIII Climate/CO2 change III Stress responses/stress avoidance I Improving food production Biotechnology Plant movements III Plant signaling (including neurobiology)VI Flowering? Regeneration? Seed germination? 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 Peroxisomes 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 ab tubulin subunits polymerize to form protofilaments (PF) PF form sheets Sheets form microtubules
Microtubules Protofilaments are polar -tubulin @ - end -tubulin @ + end all in single MT have same polarity
Microtubules In constant flux polymerizing & depolymerizing Add to (+) Fall off (-)
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 Give cells shape by guiding cellulose synth
µT functions Give cells shape by guiding cellulose synth Anchor organelles
µT functions Give cells shape by guiding cellulose synth Anchor organelles Intracellular motility