Target of rapamycin (TOR) plays a critical role in triacylglycerol accumulation in microalgae.
Most microalgae produce triacylglycerol (TAG) under stress conditions such as nitrogen depletion, but the underlying molecular mechanism remains unclear. In this study, we focused on the role of target of rapamycin (TOR) in TAG accumulation. TOR is a serine/threonine protein kinase that is highly conserved and plays pivotal roles in nitrogen and other signaling pathways in eukaryotes. We previously constructed a rapamycin-susceptible Cyanidioschyzon merolae, a unicellular red alga, by expressing yeast FKBP12 protein to evaluate the results of TOR inhibition (Imamura et al. in Biochem Biophys Res Commun 439:264-269, 2013). By using this strain, we here report that rapamycin-induced TOR inhibition results in accumulation of cytoplasmic lipid droplets containing TAG. Transcripts for TAG synthesis-related genes, such as glycerol-3-phosphate acyltransferase and acyl-CoA:diacylglycerol acyltransferase (DGAT), were increased by rapamycin treatment. We also found that fatty acid synthase-dependent de novo fatty acid synthesis was required for the accumulation of lipid droplets. Induction of TAG and up-regulation of DGAT gene expression by rapamycin were similarly observed in the unicellular green alga, Chlamydomonas reinhardtii. These results suggest the general involvement of TOR signaling in TAG accumulation in divergent microalgae.
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan. simamura@res.titech.ac.jp.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama, 332-0012, Japan. simamura@res.titech.ac.jp.
Sousuke
S
Imamura
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.
Yasuko
Y
Kawase
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.
Ikki
I
Kobayashi
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.
Toshiyuki
T
Sone
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama, 332-0012, Japan.|Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan.
Atsuko
A
Era
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama, 332-0012, Japan.|Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan.
Shin-Ya
SY
Miyagishima
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B1 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
Mie
M
Shimojima
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama, 332-0012, Japan.|Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B1 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.|Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan.
Hiroyuki
H
Ohta
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan. kntanaka@res.titech.ac.jp.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama, 332-0012, Japan. kntanaka@res.titech.ac.jp.
Kan
K
Tanaka
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D058086:Microalgae / Q000502:physiology*; D009584:Nitrogen; D000461:Rhodophyta / Q000235:genetics / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*; D015854:Up-Regulation
D020418:Algal Proteins; D014280:Triglycerides; D058570:TOR Serine-Threonine Kinases; D009584:Nitrogen
Chlamydomonas reinhardtii; Cyanidioschyzon merolae; Lipid droplet; Microalga; Target of rapamycin; Triacylglycerol