Target of Rapamycin Inhibition in Chlamydomonas reinhardtii Triggers de Novo Amino Acid Synthesis by Enhancing Nitrogen Assimilation[OPEN]

TOR inhibition leads to an immediate and substantial accumulation of amino acids, which is driven by an increase in nitrogen assimilation and amino acid synthesis. The Target of Rapamycin (TOR) kinase is a central regulator of growth and metabolism in all eukaryotic organisms, including animals, fungi, and plants. Even though the inputs and outputs of TOR signaling are well characterized for animals and fungi, our understanding of the upstream regulators of TOR and its downstream targets is still fragmentary in photosynthetic organisms. In this study, we employed the rapamycin-sensitive green alga Chlamydomonas reinhardtii to elucidate the molecular cause of the amino acid accumulation that occurs after rapamycin-induced inhibition of TOR. Using different growth conditions and stable 13C- and 15N-isotope labeling, we show that this phenotype is accompanied by increased nitrogen (N) uptake, which is induced within minutes of TOR inhibition. Interestingly, this increased N influx is accompanied by increased activities of glutamine synthetase and glutamine oxoglutarate aminotransferase, the main N-assimilating enzymes, which are responsible for the rise in levels of several amino acids, which occurs within a few minutes. Accordingly, we conclude that even though translation initiation and autophagy have been reported to be the main downstream targets of TOR, the upregulation of de novo amino acid synthesis seems to be one of the earliest responses induced after the inhibition of TOR in Chlamydomonas.

• Publication year

  2018

• Venue

  The Plant Cell

• Publication date

  2018-09-18

• Fields of study

  Biology, Medicine, Environmental Science

• Identifiers
  DOI 10.1105/tpc.18.00159PMID 30228127PMCID PMC6241278
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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