ABSTRACT
Although a growing number of mechanosensitive ion channels are being identified in plant systems, the molecular mechanisms by which they function remain to be established. 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 regulated 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 point mutation in the soluble C-terminus (S640L). In all cases, these gain-of-function phenotypes were suppressed by growth at elevated temperatures. 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. Finally, transcriptomic analysis revealed that the complex network of genes induced by these gain-of-function MSL10 alleles overlap with established biotic and abiotic stress-responsive pathways. We propose a three-step model by which tension-activated conformational changes in the C-terminus activate 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.
