1.A.23.4.7
Mechanosensitive ion channel protein 8 (Mechanosensitive channel of small conductance-like 8) (MscS-like protein 8, Msl8) is a pollen-specific, membrane tension-gated ion channel required for pollen to survive the hypoosmotic shock of rehydration and for full male fertility. It negatively regulates pollen germination but is required for cellular integrity during germination and tube growth. MSL8 thus senses and responds to changes in membrane tension associated with pollen hydration and germination (Hamilton et al. 2015).  Mechanosensitive ion channels, MSL8, MSL9, and MSL10, have environmentally sensitive intrinsically disordered regions with distinct biophysical characteristics (Flynn et al. 2023).  Intrinsically disordered protein regions (IDRs) are highly dynamic sequences that rapidly sample a collection of conformations over time. In the past several decades, IDRs have emerged as major components of many proteomes, comprising ~30% of all eukaryotic protein sequences. Proteins with IDRs function in a wide range of biological pathways and are notably enriched in signaling cascades that respond to environmental stresses. Flynn et al. 2023 identified and characterized intrinsic disorder in the soluble cytoplasmic N-terminal domains of MSL8, MSL9, and MSL10, three members of the MscS-like (MSL) family of mechanosensitive ion channels. In plants, MSL channels are proposed to mediate cell and organelle osmotic homeostasis. See TC# 1.A.23.4.14 for details of MSL10.