Homeostasis of branched-chain amino acids is critical for the activity of TOR signaling in Arabidopsis

Abstract

The target of rapamycin (TOR) kinase is an evolutionarily conserved hub of nutrient sensing and metabolic signaling. In plants, a functional connection of TOR activation with glucose availability was demonstrated, while it is yet unclear whether branched-chain amino acids (BCAAs) are a primary input of TOR signaling as they are in yeast and mammalian cells. Here, we report on the characterization of an Arabidopsis mutant over-accumulating BCAAs. Through chemical interventions targeting TOR and by examining mutants of BCAA biosynthesis and TOR signaling, we found that BCAA over-accumulation leads to up-regulation of TOR activity, which causes reorganization of the actin cytoskeleton and actin-associated endomembranes. Finally, we show that activation of TOR is concomitant with alteration of cell expansion, proliferation and specialized metabolism, leading to pleiotropic effects on plant growth and development. These results demonstrate that BCAAs contribute to plant TOR activation and reveal previously uncharted downstream subcellular processes of TOR signaling.

Data availability

All data generated or analyzed in this study have been included in the manuscript and the supporting files.

Article and author information

Author details

  1. Pengfei Cao

    MSU-DOE Plant Research Lab, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6998-9302
  2. Sang-Jin Kim

    Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Anqi Xing

    Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Craig A Schenck

    Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-5711-7213
  5. Lu Liu

    MSU-DOE Plant Research Lab, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Nan Jiang

    Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Jie Wang

    Department of Plant Biology, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
  8. Robert L Last

    Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6974-9587
  9. Federica Brandizzi

    MSU-DOE Plant Research Lab, Michigan State University, East Lansing, United States
    For correspondence
    fb@msu.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-0580-8888

Funding

National Science Foundation (MCB1727362)

  • Federica Brandizzi

National Institute of Food and Agriculture (MICL02299)

  • Federica Brandizzi

National Science Foundation (NPGI-1811055)

  • Craig A Schenck

U.S. Department of Energy (DE-FG02-91ER20021)

  • Federica Brandizzi

U.S. Department of Energy (DE-FC02-07ER64494)

  • Federica Brandizzi

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

© 2019, Cao et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 4,634
    views
  • 759
    downloads
  • 75
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Pengfei Cao
  2. Sang-Jin Kim
  3. Anqi Xing
  4. Craig A Schenck
  5. Lu Liu
  6. Nan Jiang
  7. Jie Wang
  8. Robert L Last
  9. Federica Brandizzi
(2019)
Homeostasis of branched-chain amino acids is critical for the activity of TOR signaling in Arabidopsis
eLife 8:e50747.
https://doi.org/10.7554/eLife.50747

Share this article

https://doi.org/10.7554/eLife.50747

Further reading

    1. Biochemistry and Chemical Biology
    2. Plant Biology
    Hao Wang, Biying Zhu ... Zhaoliang Zhang
    Research Article

    Ethylamine (EA), the precursor of theanine biosynthesis, is synthesized from alanine decarboxylation by alanine decarboxylase (AlaDC) in tea plants. AlaDC evolves from serine decarboxylase (SerDC) through neofunctionalization and has lower catalytic activity. However, lacking structure information hinders the understanding of the evolution of substrate specificity and catalytic activity. In this study, we solved the X-ray crystal structures of AlaDC from Camellia sinensis (CsAlaDC) and SerDC from Arabidopsis thaliana (AtSerDC). Tyr341 of AtSerDC or the corresponding Tyr336 of CsAlaDC is essential for their enzymatic activity. Tyr111 of AtSerDC and the corresponding Phe106 of CsAlaDC determine their substrate specificity. Both CsAlaDC and AtSerDC have a distinctive zinc finger and have not been identified in any other Group II PLP-dependent amino acid decarboxylases. Based on the structural comparisons, we conducted a mutation screen of CsAlaDC. The results indicated that the mutation of L110F or P114A in the CsAlaDC dimerization interface significantly improved the catalytic activity by 110% and 59%, respectively. Combining a double mutant of CsAlaDCL110F/P114A with theanine synthetase increased theanine production 672% in an in vitro system. This study provides the structural basis for the substrate selectivity and catalytic activity of CsAlaDC and AtSerDC and provides a route to more efficient biosynthesis of theanine.

    1. Plant Biology
    Yuanyuan Bu, Xingye Dong ... Shenkui Liu
    Research Article Updated

    Urea is intensively utilized as a nitrogen fertilizer in agriculture, originating either from root uptake or from catabolism of arginine by arginase. Despite its extensive use, the underlying physiological mechanisms of urea, particularly its adverse effects on seed germination and seedling growth under salt stress, remain unclear. In this study, we demonstrate that salt stress induces excessive hydrolysis of arginine-derived urea, leading to an increase in cytoplasmic pH within seed radical cells, which, in turn, triggers salt-induced inhibition of seed germination (SISG) and hampers seedling growth. Our findings challenge the long-held belief that ammonium accumulation and toxicity are the primary causes of SISG, offering a novel perspective on the mechanism underlying these processes. This study provides significant insights into the physiological impact of urea hydrolysis under salt stress, contributing to a better understanding of SISG.