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Plant Molecular Biology

, Volume 89, Issue 3, pp 309–318 | Cite as

Target of rapamycin (TOR) plays a critical role in triacylglycerol accumulation in microalgae

  • Sousuke Imamura
  • Yasuko Kawase
  • Ikki Kobayashi
  • Toshiyuki Sone
  • Atsuko Era
  • Shin-ya Miyagishima
  • Mie Shimojima
  • Hiroyuki Ohta
  • Kan Tanaka
Article

Abstract

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.

Keywords

Chlamydomonas reinhardtii Cyanidioschyzon merolae Lipid droplet Microalga Target of rapamycin Triacylglycerol 

Notes

Acknowledgments

We thank Ms. A. Ishiwata and Dr. M. Iwai for their technical assistance and technical advice, respectively. This study was supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (Grants-in-Aid 22681010, 24117521, 25440129 and 26117711 to S.I. and Grants-in-Aid 24248061 to K.T.).

Supplementary material

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Sousuke Imamura
    • 1
    • 2
  • Yasuko Kawase
    • 1
  • Ikki Kobayashi
    • 1
  • Toshiyuki Sone
    • 1
  • Atsuko Era
    • 2
    • 3
  • Shin-ya Miyagishima
    • 2
    • 3
  • Mie Shimojima
    • 4
  • Hiroyuki Ohta
    • 2
    • 4
    • 5
  • Kan Tanaka
    • 1
    • 2
  1. 1.Chemical Resources LaboratoryTokyo Institute of TechnologyYokohamaJapan
  2. 2.Core Research for Evolutional Science and Technology (CREST)Japan Science and Technology Agency (JST)SaitamaJapan
  3. 3.Department of Cell GeneticsNational Institute of GeneticsMishimaJapan
  4. 4.Graduate School of Bioscience and BiotechnologyTokyo Institute of TechnologyYokohamaJapan
  5. 5.Earth-Life Science InstituteTokyo Institute of Technology Tokyo Japan

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