Interactions between the N- and C- termini of mechanosensitive ion channel AtMSL10 are consistent with a three-step mechanism for activation

Abstract

Although a growing number of mechanosensitive ion channels are being identified in plant systems, the molecular mechanisms by which they function are still under investigation. Overexpression of the mechanosensitive ion channel MSL (MscS-Like)10 fused to GFP triggers a number of developmental and cellular phenotypes including the induction of cell death, and this function is influenced by seven phosphorylation sites in its soluble N-terminus. Here, we show that these and other phenotypes required neither overexpression nor a tag and could be also induced by a previously identified point mutation in the soluble C-terminus (S640L). The promotion of cell death and hyperaccumulation of H2O2 in 35S:MSL10S640L-GFP overexpression lines was suppressed by N-terminal phosphomimetic substitutions, and the soluble N- and C-terminal domains of MSL10 physically interacted. We propose a three-step model by which tension-induced conformational changes in the C-terminus are transmitted to the N-terminus, leading to its dephosphorylation and the induction of adaptive responses. Taken together, this work expands our understanding of the molecular mechanisms of mechanotransduction in plants. HIGHLIGHTCell death is triggered by mutations in either the cytoplasmic N- or C-terminus of AiMSLlu. Our proposed model explains how membrane tension may activate signaling through the interaction of these two domains.