1. 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

2. 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

3. 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)

4. 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

5. 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”)

6. 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!

7. Lipid metabolism
Unique aspects in plants
Chloroplasts have lots
of galactolipids: sugar
linked directly to
diacylglycerol

8. Lipid metabolism
Unique aspects in plants
Chloroplasts have lots
of galactolipids: sugar
linked directly to
diacylglycerol: saves PO4

9. 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!

10. 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

11. 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

12. 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!

13. 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

14. 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

15. Lipid metabolism
Unique aspects in plants
Make fatty acids in plastids
large amounts of galactolipids
Oleosomes: oil-storing organelles with only outer leaflet

16. Lipid metabolism
Oleosomes: oil-storing organelles with only outer leaflet
Put oils between the leaflets as they are made

17. 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

18. 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

19. Lipid metabolism
Use fats to store carbon as well as energy!!??
Recover C via glyoxylate cycle & gluconeogenesis

20. Lipid metabolism
Biological roles
Plasma membrane lipids help
survive freezing

21. Lipid metabolism
Biological roles
Plasma membrane lipids help
survive freezing
Unacclimated cells vesiculate as
they lose water & pop when it returns

22. 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

23. 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

24. 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
Mito show defects at <10˚ C not seen in other plants

25. 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

26. 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

27. 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

28. Lipid metabolism
Other commercial aspects
Yield and quality of seed oil is very important:12 million tons/year

29. 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

30. 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

31. 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

32. 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