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 Make fatty acids in plastids large amounts of galactolipids 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 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

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

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

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