1. 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

2. Lipid metabolism
Acetyl-CoA carboxylase is also prokaryotic = 4 subunits, except in grasses (profoxydim & other herbicides inhibit ACCase)
Same biochem, but diff
location and enzymes
In light cp make lots of
NADPH, and leaves are
main sinks for FA
But, each cell makes
its own FA, so NADPH
in other cells comes from
Pentose-Pi shunt

3. 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”)

4. 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!

5. 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 ( Sulphoquinovosyl diacylglycerol) 16% cp

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. Lipid metabolism
Biofuels are now very fashionable
Biodiesel = fatty acid methyl esters
Trans-esterify oils to make them volatile

14. Lipid metabolism
Biofuels are now very fashionable
Biodiesel = fatty acid methyl esters
Trans-esterify oils to make them volatile
Projected to be 10% of european diesel in 2018

15. Lipid metabolism
Biofuels are now very fashionable
Biodiesel = fatty acid methyl esters
Trans-esterify oils, used cooking oil, etc
Projected to be 10% of european diesel in 2018
Also use coconut & other oils directly in diesel engines

16. Lipid metabolism
Also use coconut & other oils directly in diesel engines
Just need to be sufficiently fluid to reach cylinder

17. Lipid metabolism
Also use coconut & other oils directly in diesel engines
Just need to be sufficiently fluid to reach cylinder
Add double bonds to fatty acids or make them shorter

18. Lipid metabolism
Also use coconut & other oils directly in diesel engines
Just need to be sufficiently fluid to reach cylinder
Add double bonds to fatty acids or make them shorter
Problem: shifting from growing food to growing fuel!

19. Biofuels

20. Biofuels
1st gen Ethanol
Yeast makes EtOH from plant sugar
Corn, sugar cane, sugar beet, sorghum

21. Biofuels
1st gen Ethanol
Yeast makes EtOH from plant sugar
Corn, sugar cane, sugar beet, sorghum
Only use part of plant

22. Biofuels
1st gen Ethanol
Yeast makes EtOH from plant sugar
Corn, sugar cane, sugar beet, sorghum
Only use part of plant
Can yield 1.3x more energy than needed to grow, harvest & convert it to ethanol

23. Biofuels
1st gen Ethanol
Yeast makes EtOH from plant sugar
Corn, sugar cane, sugar beet, sorghum
Only use part of plant
Can yield 1.3x more energy than needed to grow, harvest & convert it to ethanol
Usually lose C

24. Biofuels
Yeast makes EtOH from plant sugar
Corn, sugar cane, sugar beet, sorghum
Only use part of plant
Can yield 1.3x more energy than needed to grow, harvest & convert it to ethanol
Usually lose C
Use crops for fuel instead of food

25. Biofuels
1st gen Ethanol
Yeast makes EtOH from plant sugar
Inefficient
Only use part of plant
Use crops for fuel instead of food
2nd gen (cellulosic) Ethanol
Use cell walls as source of sugar for yeast

26. Biofuels
2nd gen (cellulosic) Ethanol
Use cell walls as source of sugar for yeast
Can use entire plant

27. Biofuels
1st gen Ethanol
Yeast makes EtOH from plant sugar
Corn, sugar cane, sugar beet, sorghum
Only use part of plant
Use crops for fuel instead of food
2nd gen (cellulosic) Ethanol
Use cell walls as source of sugar for yeast

28. Biofuels
2nd gen (cellulosic) Ethanol
Use cell walls as source of sugar for yeast
Can use entire plant
Can use non-crops grown on marginal land
Switchgrass (Panicum virgatum)
C4 perennial: grows from Mexico to 55˚ N

29. Biofuels
Switchgrass (Panicum virgatum)
Can yield 5.4 x more energy than needed to
grow, harvest & convert it to ethanol cf 1.3 x
max for corn
Also used for soil conservation and
phytoremediation

30. Biofuels
Miscanthus giganteus
Sterile hybrid of M. sinensis X M. sacchariflorus (both from Asia)

31. Biofuels
Miscanthus giganteus
Sterile hybrid of M. sinensis & M. sacchariflorus (both from Asia)
C4 perennial that reproduces solely through rhizomes

32. Biofuels
Miscanthus giganteus
Sterile hybrid of M. sinensis & M. sacchariflorus (both from Asia)
C4 perennial that reproduces solely through rhizomes
Non-invasive cf both parents, even though grows > 4m tall cf 1-2 m max for both parents

33. Biofuels
Miscanthus giganteus
Non-invasive cf both parents, even though grows > 4m tall cf 1-2 m max for both parents
High N efficiency + C4 = grows well on barren land

34. Biofuels
Miscanthus giganteus
Non-invasive cf both parents, even though grows > 4m tall cf 1-2 m max for both parents
High N efficiency + C4 = grows well on barren land
Can yield 20 tons biomass/acre cf 7.6 for corn & 6 for switchgrass

35. Biofuels
Miscanthus giganteus
Can yield 20 tons biomass/acre cf 7.6 for corn & 6 for switchgrass
could supply 12% of the EU's energy by 2050
Trees
Poplar

36. Biofuels
Trees
Poplar
Eucalyptus
Can be harvested in 4-5 years
Low maintenance
Yield <4 tons
biomass/acre cf 20
for M. giganteus

37. Biofuels
2nd gen (cellulosic) Ethanol
Use cell walls as source of sugar for yeast
Can use entire plant
Can use non-crops grown on marginal land
Problem: lignin & other wall chems

38. Biofuels
Mutate plants to make simpler cell walls
10% of Arabidopsis genes are estimated to be involved in plant cell wall metabolism
Many mutants reduce lignin synthesis
Easier to digest cell walls
Easier for pathogens to attack
More prone to xylem collapse

39. Biofuels
Biodiesel = fatty acid methyl esters
Trans-esterify oils to make them volatile
Renewable Fuels Standard (RFS2): US must use > 1 billion gallons/year in 2012 through 2022 (cf ~40 billion/year total)
> 50% reduction in CO2 cf petrodiesel
2.1 billion gallons of biodiesel were used in 2015
Diamond Green Diesel in LA makes 275 million gallons/year

40. Biofuels
Oils from plants and algae

41. Biofuels
Algal oil production