Transcript Bio 226: Cell and Molecular Biology

Next Assignment = GMO plants
In class starting March 27
Herbicide resistance
• Bromoxynil
• Glyphosate (roundup)
• Glufosinate (Basta)
• Isoxaflutole (Balance, Corvus, Prequel)
• Dicamba/2,4-D
•Pathogen/herbivore resistance
• BT (Bacillus thuringiensis toxin)
• Colorado Potato Beetle (CPB) Resistant NewLeaf Potato
• Papaya Ring Spot Virus Resistant Papaya
•Improving nutrition
• Golden rice
• Potato: reducing acrylamide
•Improving shelf-life
• FlavrSavr tomato.
•Making vaccines, other useful biochems
Lipid metabolism
Unique aspects in plants
Make fatty acids by
same reactions, but in
plastids with a prokaryotic
fatty acid synthase
12 proteins, cf one
multifunctional
protein
Lipid metabolism
Make fatty acids in plastids with a prokaryotic FAS
• 12 proteins, instead of one multifunctional protein
• Assemble some lipids in CP, others in ER
• Acetyl-CoA carboxylase is also prokaryotic = 4 subunits, except
in grasses (profoxydim & other grass herbicides inhibit ACCase)
Lipid metabolism
Source of acetyl-CoA is controversial
• Most comes from plastid PDH
• Some comes from cytoplasmic acetate; activated in cp
• Also used to make
sterols, some amino
acids, many others
Lipid metabolism
“16:3 plants” assemble lipids in cp using FA-ACP = prokaryotic
pathway (“primitive”)
“18:3 plants” export FA, assemble lipids in ER using FA-CoA =
eukaryotic pathway (“advanced”)
Lipid metabolism
“16:3 plants” assemble lipids in cp using FA-ACP = prokaryotic
pathway (“primitive”)
“18:3 plants” export FA, assemble lipids in ER using FA-CoA =
eukaryotic pathway (“advanced”)
Substrates for most desaturases
are lipids, not FA!
Lipid metabolism
Unique aspects in plants
Chloroplasts have lots
of galactolipids: sugar
linked directly to
diacylglycerol
Lipid metabolism
Unique aspects in plants
Chloroplasts have lots
of galactolipids: sugar
linked directly to
diacylglycerol: saves PO4
Lipid metabolism
Unique aspects in plants
Chloroplasts have lots of galactolipids: sugar linked directly to
diacylglycerol : saves PO4
A) MGDG (Monogalactosyl diacylglycerol) 50% cp
-> most abundant lipid on earth!
Lipid metabolism
Unique aspects in plants
Chloroplasts have lots of galactolipids: sugar linked directly to
diacylglycerol : saves PO4
A) MGDG (Monogalactosyl diacylglycerol) 50% cp
B) DGDG (Digalactosyl diacylglycerol) 28% cp
Lipid metabolism
Chloroplasts have lots of galactolipids: sugar linked directly to
diacylglycerol : saves PO4
A) MGDG (Monogalactosyl diacylglycerol) 50% cp
B) DGDG (Digalactosyl diacylglycerol) 28% cp
C) SQDG ( Sulphoquinovosyldiacylglycerol) 16% cp
Lipid metabolism
Chloroplasts have lots of galactolipids: sugar linked directly to
diacylglycerol : saves PO4
A) MGDG (Monogalactosyl diacylglycerol) 50% cp
B) DGDG (Digalactosyl diacylglycerol) 28% cp
C) SQDG ( Sulphoquinovosyldiacylglycerol) 16% cp
• Very unsaturated!
Lipid metabolism
Chloroplasts have lots of galactolipids: sugar linked directly to
diacylglycerol : saves PO4
A) MGDG (Monogalactosyl diacylglycerol) 50% cp
B) DGDG (Digalactosyl diacylglycerol) 28% cp
C) SQDG ( Sulphoquinovosyldiacylglycerol) 16% cp
• Very unsaturated!
• Makes membranes
very fluid
Lipid metabolism
Chloroplasts have lots of galactolipids: sugar linked directly to
diacylglycerol : saves PO4
A) MGDG (Monogalactosyl diacylglycerol) 50% cp
B) DGDG (Digalactosyl diacylglycerol) 28% cp
C) SQDG ( Sulphoquinovosyldiacylglycerol) 16% cp
• Very unsaturated!
• Makes membranes
very fluid
• Source of 3 FA
Lipid metabolism
Unique aspects in plants
1) Make fatty acids in plastids
2) large amounts of galactolipids
3) Oleosomes: oil-storing organelles with only outer leaflet
Lipid metabolism
Oleosomes: oil-storing organelles with only outer leaflet
• Put oils between the leaflets as they are made
Lipid metabolism
Oleosomes: oil-storing organelles with only outer leaflet
• Put oils between the leaflets as they are made
• Add oleosin proteins to outside: curve the membrane
Lipid metabolism
Oleosomes: oil-storing organelles with only outer leaflet
• Put oils between the leaflets as they are made
• Add oleosin proteins to outside: curve the membrane
• Oils often have unusual fatty acids
Lipid metabolism
Use fats to store carbon as well as energy!!??
• Recover C via glyoxylate cycle & gluconeogenesis
Lipid metabolism
Biological roles
• Plasma membrane lipids help
survive freezing
Lipid metabolism
Biological roles
• Plasma membrane lipids help
survive freezing
• Unacclimated cells vesiculate as
they lose water & pop when it returns
Lipid metabolism
Biological roles
• Plasma membrane lipids help
survive freezing
• Unacclimated cells vesiculate as
they lose water & pop when it returns
• Acclimated cells shrivel & reswell
Lipid metabolism
Biological roles
• Plasma membrane lipids help survive freezing
• Mito lipid composition may also influence chilling sensitivity
• CS plants (eg bananas) are damaged at 10˚ C
Lipid metabolism
log respiration (nmol O2/min/mg protein)
Biological roles
• Plasma membrane lipids help survive freezing
• Mito lipid composition may also influence chilling sensitivity
• CS plants (eg bananas) are damaged at 10˚ C
• Mito show defects at <10˚ C not seen in other plants
3.0
B) SB-H mitochondria
A) fr2 x fr1 mitochondria
34°
2.8
2.6
18°
2.4
35°
25°
24°
2.2
2.0
16°
Control
17:0
18:1
Control
17:0
18:1
1.8
3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 3.15
3.60 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 3.60
1/T (°K x 1000)
1/T (°K x 1000)
Lipid metabolism
CS plants (eg bananas) are damaged at 10˚ C
• Mito show defects at <10˚ C not seen in other plants
• Membrane lipids show phase changes at these T
Lipid metabolism
CS plants (eg bananas) are damaged at 10˚ C
• Mito show defects at <10˚ C not seen in other plants
• Membrane lipids show phase changes at these T
• Blamed on saturated PG
log respiration (nmol O2/min/mg protein)
Lipid metabolism
Biological (& commercial) roles
• Plasma membrane lipids help survive freezing
• Mito lipid composition influences chilling sensitivity
• Mito show defects at <10˚ C not seen in other plants
•
unsaturated FA did not fix CS, but saturated FA made it
worse: reason for GM desaturases
3.0
B) SB-H mitochondria
A) fr2 x fr1 mitochondria
34°
2.8
2.6
18°
2.4
35°
25°
24°
2.2
2.0
16°
Control
17:0
18:1
Control
17:0
18:1
1.8
3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 3.15
3.60 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 3.60
1/T (°K x 1000)
1/T (°K x 1000)
Lipid metabolism
Other commercial aspects
• Yield and quality of seed oil is very important:12 million
tons/year
Lipid metabolism
Other commercial aspects
• Yield and quality (especially unsaturation) of seed oil is very
important:12 million tons/year
• Want more double bonds, especially w-3, for health
• Want less double bonds for shelf life and taste
• Each double bond increases p(oxidation) 40x
Lipid metabolism
Other commercial aspects
• Yield and quality (especially unsaturation) of seed oil is very
important:12 million tons/year
• Want more double bonds, especially w-3, for health
• Want less double bonds for shelf life and taste
• Each double bond increases p(oxidation) 40x
• Have GM oils with more & less double bonds
Lipid metabolism
Other commercial aspects
• Yield and quality of seed oil is very important:12 million tons/yr
• Also have markets for many specialized oils
Lipid metabolism
Other commercial aspects
• Yield and quality of seed oil is very important
• Also have markets for many specialized oils
• Have genetically-engineered many crops to alter seed oils or
produce specific fats