Arabidopsisplasma membrane protein crucial for Ca2+influx and touch sensing in roots

Plants can sense and respond to mechanical stimuli, like animals. An early mechanism of mechanosensing and response is speculated to be governed by as-yet-unidentified sensory complexes containing a Ca 2+ -permeable, stretch-activated (SA) channel. However, the components or regulators of such complexes are poorly understood at the molecular level in plants. Here, we report the molecular identification of a plasma membrane protein (designated Mca1) that correlates Ca 2+ influx with mechanosensing in Arabidopsis thaliana . MCA1 cDNA was cloned by the functional complementation of lethality of a yeast mid1 mutant lacking a putative Ca 2+ -permeable SA channel component. Mca1 was localized to the yeast plasma membrane as an integral membrane protein and mediated Ca 2+ influx. Mca1 also increased [Ca 2+ ] cyt upon plasma membrane distortion in Arabidopsis . The growth of MCA1 -overexpressing plants was impaired in a high-calcium but not a low-calcium medium. The primary roots of mca1 -null plants failed to penetrate a harder agar medium from a softer one. These observations demonstrate that Mca1 plays a crucial role in a Ca 2+ -permeable SA channel system that leads to mechanosensing in Arabidopsis . We anticipate our findings to be a starting point for a deeper understanding of the molecular mechanisms of mechanotransduction in plants.