*MS Channels in the Plastid Envelope

Our studies on the plastid-localized Arabidopsis MscS homologs MSL2 and MSL3 has revealed how organelles use these proteins to respond to membrane stretch, how their activity is integrated into cellular signaling networks, and how plants adjust to their absence. These results suggest that plant MscS homologs are not merely safety valves but regulated channels with multiple roles at the organellar, cellular, and organismal level.

*Role of MS Channels in Pollen Development

MscS is a non-selective mechanosensitive ion channel that is gated directly through tension in the membrane, and serves as an osmotic release valve during hypoosmotic swelling. We have been asking the question: what physiological function do homologs of Ec-MscS homologs in play in the model flowering plant Arabidopsis thaliana? We discovered that MSL8 as been repurposed to regulate osmotic forces during pollen hydration and germination.

*Mechanosensitive Channels & Plant Gravity Perception

In the gravity-sensing cells of the root tip, mechanosensitive channels have been proposed to mediate gravity perception from the envelope of sedimenting amyloplasts (1), and from the ER onto which amyloplasts sediment (2). In all cells, mechanosensitive channels could mediate gravity perception from the plasma membrane (3). We aim to investigate the role played by MSL and other mechanosensitive channels in the perception of and response to gravity.

*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.

*Structural, Functional, and Regulatory Diversity in the MscS Family

MscS homologs are widely dispersed among bacterial and plant lineages, are found in some fungi, but have not been identified in plants. Our investigations are beginning to reveal much how MscS-Like proteins have diverged with respect to structure, function and mechanisms of regulation.We have recently discovered that plant-specific domains confer plant-specific functions and modes of regulation to MscS-Like proteins in Arabidopsis thaliana.