AtMSL9 and AtMSL10: Sensors of plasma membrane tension in Arabidopsis roots

Abstract

Plant cells, like those of animals and bacteria, are able to sense physical deformation of the plasma membrane. Mechanosensitive (MS) channels are proteins that transduce mechanical force into ion flux, providing a mechanism for the perception of mechanical stimuli such as sound, touch and osmotic pressure. We recently identified AtMSL9 and AtMSL10, two mechanosensitive channels in Arabidopsis thaliana, as molecular candidates for mechanosensing in higher plants. AtMSL9 and AtMSL10 are members of a family of proteins in Arabidopsis that are related to the bacterial MS channel MscS, termed MscS-Like (or MSL). MscS (Mechanosensitive channel of Small conductance) is one of the best-characterized MS channels, first identified as an electrophysiological activity in the plasma membrane (PM) of giant E. coli spheroplasts. Activation of MscS is voltage-independent, but responds directly to tension applied to the membrane and does not require other cellular proteins for this regulation. MscS family members are widely distributed throughout bacterial and archaeal genomes, are present in all plant genomes yet examined, and are found in selected fungal genomes. MscS homolgues have not yet been identified in animals.We previously showed that in wild type protoplasts from the Arabidopsis root, AtMSL9 and AtMSL10 function cooperatively to provide a characteristic WT activity. In this paper, we further investigate the function of AtMSL9 and AtMSL10. We analyze individual protoplasts and argue that in WT cells AtMSL9 and AtMSL10 can function either in cooperation or independently. We also compare the electrophysiological properties of these two channels with that of their bacterial and algal counterparts, and discuss their possible function in planta.Addendum to: Haswell ES, Peyronnet R, Barbier-Brygoo H, Meyerowitz EM, Frachisse J-M. Two MscS homologs provide mechanosensitive channel activities in the Arabidopsis root. Curr Biol 2008; 18:730-4.