Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 115, Issue 39, Pages 9785-9790Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1809611115
Keywords
ethanolamine; LuxR homolog; plant-microbe interactions; transcription activator; quorum sensing
Categories
Funding
- NIH [R01AT009708]
- Genomic Science Program, US Department of Energy, Office of Science, Biological and Environmental Research as part of the Plant Microbe Interfaces Scientific Focus Area
- US Department of Energy [DE-AC05-00OR227525]
- National Center for Complementary & Integrative Health [R01AT009708] Funding Source: NIH RePORTER
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Certain plant-associated Proteobacteria sense their host environment by detecting an unknown plant signal recognized by a member of a LuxR subfamily of transcription factors. This interkingdom communication is important for both mutualistic and pathogenic interactions. The Populus root endophyte Pseudomonas sp. GM79 possesses such a regulator, named PipR. In a previous study we reported that PipR activates an adjacent gene (pipA) coding for a proline iminopeptidase in response to Populus leaf macerates and peptides and that this activation is dependent on a putative ABCtype transporter [Schaefer AL, et al. (2016) mBio 7: e01101-16]. In this study we identify a chemical derived from ethanolamine that induces PipR activity at picomolar concentrations, and we present evidence that this is the active inducer present in plant leaf macerates. First, a screen of more than 750 compounds indicated ethanolamine was a potent inducer for the PipR-sensing system; however, ethanolamine failed to bind to the periplasmic-binding protein (PBP) required for the signal response. This led us to discover that a specific ethanolamine derivative, N-(2-hydroxyethyl)-2-(2-hydroxyethylamino) acetamide (HEHEAA), binds to the PBP and serves as a potent PipR-dependent inducer. We also show that a compound, which coelutes with HEHEAA in HPLC and induces pipA gene expression in a PipRdependent manner, can be found in Populus leaf macerates. This work sheds light on how plant-associated bacteria can sense their environment and on the nature of inducers for a family of plant-responsive LuxR-like transcription factors found in plant-associated bacteria.
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