OzTracs: Optical Osmolality Reporters Engineered from Mechanosensitive Ion Channels

Thomas J. Kleist, I. Winnie Lin, Sophia Xu, Grigory Maksaev, Mayuri Sadoine, Elizabeth S. Haswell, Wolf B. Frommer, Michael M. Wudick

Research output: Contribution to journalArticlepeer-review


Interactions between physical forces and membrane proteins underpin many forms of environmental sensation and acclimation. Microbes survive osmotic stresses with the help of mechanically gated ion channels and osmolyte transporters. Plant mechanosensitive ion channels have been shown to function in defense signaling. Here, we engineered genetically encoded osmolality sensors (OzTracs) by fusing fluorescent protein spectral variants to the mechanosensitive ion channels MscL from E. coli or MSL10 from A. thaliana. When expressed in yeast cells, the OzTrac sensors reported osmolality changes as a proportional change in the emission ratio of the two fluorescent protein domains. Live-cell imaging revealed an accumulation of fluorescent sensors in internal aggregates, presumably derived from the endomembrane system. Thus, OzTrac sensors serve as osmolalitydependent reporters through an indirect mechanism, such as effects on molecular crowding or fluorophore solvation.

Original languageEnglish
Article number787
Issue number6
StatePublished - Jun 2022


  • mechanosensitive protein
  • osmolality
  • sensor
  • yeast


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