A Plant-Responsive Bacterial Signaling System Senses an Ethanolamine Derivative

Summary

Objective

Advance the understanding of non–acyl-HSL–responsive LuxR homologs and how these transcription factors might be responding to their plant host environments.

Approach

• To identify a more active PipR coinducer of pipA expression using Pseudomonas GM79 with ΔpipA ΔaapA mutations containing pPpipA-gfp.

Results/Impact

• Identified N-(2-hydroxyethyl)-2-(2-hydroxyethylamino) acetamide (HEHEAA) as the compound that binds to the ABC transporter and serves as a potent (pM) PipR-dependent inducer.
• Bioassay-active material in Populus leaf macerates co-elutes with HEHEAA by HPLC fractionation, suggesting HEHEAA is present in plant macerates.
• HEHEAA forms spontaneously from ethanolamine (EA), a component of plant phospholipids.
• Identification of a GM79 PipR activator sets the stage for understanding interkingdom signaling and for identifying plant-derived signals for other PipR receptors, which are present in dozens of bacterial species associated with economically important plants.

References

Coutinho, B.G. et al. “A plant-responsive bacterial-signaling system senses an ethanolamine derivative.” Proceedings of the National Academy of Sciences USA 115(39), 9785–9790. (2018). [DOI:10.1073/pnas.1809611115]