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

Nakagawa, Yuko, Katagiri, Takeshi, Shinozaki, Kazuo, Qi, Zhi, Tatsumi, Hitoshi, Furuichi, Takuya, Kishigami, Akio, Sokabe, Masahiro, Kojima, Itaru, Sato, Shusei, Kato, Tomohiko, Tabata, Satoshi, Iida, Kazuko, Terashima, Asuka, Nakano, Masataka, Ikeda, Mitsunobu, Yamanaka, Takuya, Iida, Hidetoshi
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.9 pp. 3639-3644
Arabidopsis thaliana, roots, root growth, thigmotropism, membrane proteins, plasma membrane, calcium channels, calcium, physiological transport, complementary DNA, nucleotide sequences, gene expression, messenger RNA
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 Ca²⁺-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 Ca²⁺ influx with mechanosensing in Arabidopsis thaliana. MCA1 cDNA was cloned by the functional complementation of lethality of a yeast mid1 mutant lacking a putative Ca²⁺-permeable SA channel component. Mca1 was localized to the yeast plasma membrane as an integral membrane protein and mediated Ca²⁺ influx. Mca1 also increased [Ca²⁺]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 Ca²⁺-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.