*Electrophysiology of Plant and Bacterial MS Channels

We have used single channel patch-clamp electrophysiology to characterize E. coli MscS and Arabidopsis MSL8 and MSL10 expressed in Xenopus laevis oocytes. These studies establish that MSLs are bonafide mechanosensitive ion channels, and their behavior in oocytes closely resembles MSL-dependent activities in Arabidopsis root and pollen protoplasts. Differences in the behavior of MSL10, MSL8 and MscS may have implications for their respective roles in plant and bacterial physiology. Expression in oocytes has a number of advantages, including ease of use, large patch size, access to a variety of expression levels, and the potential for use in high-throughput systems.

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana.

MSL10 provides a MS activity in a heterologous system with characteristics that correlate well with a MSL10-dependent channel activity previously studied in Arabidopsis protoplasts (Haswell, Peyronnet, et al., 2008). This discovery establishes that MscS homologs from multicellular eukaryotes are indeed MS channels. In addition, this analysis shows that similar mechanosensitive characteristics can be achieved without conservation of many of the residues previously shown to be critical for bacterial MscS function. Finally, some of the channel characteristics of MSL10 that differ significantly from those of MscS expressed in the same system—a 3-fold smaller conductance, a distinct preference for anions, and unusually slow closing kinetics—have implications for MSL10 function. They suggest that MSL10 may be involved in cellular signaling as well as osmotic stress relief and that it remains open until membrane tension is completely relieved.

  • G. Maksaev & E. S. Haswell. (2012). MscS-Like10 is a Stretch-activated Ion Channel from Arabidopsis thaliana with a Preference for Anions. PNAS 109:19015-19020.
  • G. Maksaev & E. S. Haswell. (2013). Recent Characterizations of MscS and its Homologs Provide Insights into the Basis of Ion Selectivity.  Channels 7(3): 215-220.
  • E. S. Haswell & G. E. Monschausen. (2013). A Force of Nature: Molecular Mechanisms of Mechanoperception in Plants. J. Experimental Botany 64(15):4663-80.
  • E. S. Hamilton, G. S. Jensen, G. Maksaev, Andrew Katims, Ashley Sherp and E. S. Haswell. (2015). Mechanosensitive Ion Channel MSL8 Regulates Osmotic Forces During Pollen Hydration and Germination. Science, in press.

A system for the electrophysiological analysis of both prokaryotic and eukaryotic MS channels.

MscS can be expressed in Xenopus oocytes and that it exhibits the same single-channel conductance and voltage dependence as the channel in its native environment. MscS is now one of only a few prokaryotic channels to be successfully expressed in Xenopus ooctyes. Several parameters of MscS activity in ooctyes are largely indistinguishable from that of MscS in its native membrane. In addition, MscS can now serve to calibrate the mechanosensitivity of any other channel expressed in the same oocyte and we now can use a single system for the electrophysiological characterization of both prokaryotic and eukaryotic MS channels.

  • G. Maksaev & E. S. Haswell. (2011). Expression and Characterization of the Bacterial Mechanosensitive Channel MscS in Xenopus laevis Ooctyes. Journal of General Physiology138:641-9.
  • G. Maksaev and E. S. Haswell. (2015). Expression and Characterization of Mechanosensitive Ion Channels in Xenopus Oocytes. Plant Gravitropism: Methods and Protocols. 1309:151-69.