Production of ricinoleic acid-containing monoestolide triacylglycerides in an oleaginous diatom, Chaetoceros gracilis.
Ricinoleic acid (RA), a hydroxyl fatty acid, is suitable for medical and industrial uses and is produced in high-oil-accumulating organisms such as castor bean and the ergot fungus Claviceps. We report here the efficient production of RA in a transgenic diatom Chaetoceros gracilis expressing the fatty acid hydroxylase gene (CpFAH) from Claviceps purpurea. In transgenic C. gracilis, RA content increased at low temperatures, reaching 2.2 pg/cell when cultured for 7 d at 15 °C, without affecting cell growth, and was enhanced (3.3 pg/cell) by the co-expression of a palmitic acid-specific elongase gene. Most of the accumulated RA was linked with monoestolide triacylglycerol (ME TAG), in which one RA molecule was esterified to the α position of the glycerol backbone and was further esterified at its hydroxy group with a fatty acid or second RA moiety, or 1-OH TAG, in which RA was esterified to the glycerol backbone. Overall, 80% of RA was accumulated as ME TAGs. Furthermore, exogenous RA-methyl ester suppressed the growth of wild-type diatoms in a dose-dependent manner and was rapidly converted to ME TAG. These results suggest that C. gracilis masks the hydroxyl group and accumulates RA as the less-toxic ME TAG.
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Masataka
M
Kajikawa
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Tatsuki
T
Abe
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Kentaro
K
Ifuku
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Ken-Ichi
KI
Furutani
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Dongyi
D
Yan
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Tomoyo
T
Okuda
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Akinori
A
Ando
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Shigenobu
S
Kishino
Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Jun
J
Ogawa
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Hideya
H
Fukuzawa
D019149:Bioreactors; D003001:Cloning, Molecular; D017377:Diatoms / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism; D060847:Metabolic Engineering; D006899:Mixed Function Oxygenases / Q000235:genetics; D012277:Ricinoleic Acids / Q000378:metabolism*; D014280:Triglycerides / Q000096:biosynthesis*
D012277:Ricinoleic Acids; D014280:Triglycerides; D006899:Mixed Function Oxygenases