Functional Analyses of a Putative Plasma Membrane Protein, OsMCA1, in Stress-Induced Ca²⁺ Influx in Rice

Abstract

Mechanosensing and response is speculated to involve sensory complexes containing a Ca²⁺-permeable, mechanosensitive channel. A recently-identified plasma membrane protein from Arabidopsis, MCA1, has been suggested to be involved in Ca²⁺ influx and touch sensing. We identified an MCA1 homolog, OsMCA1, in rice. In contrast to Arabidopsis in which two MCA family members are present, OsMCA1 has been shown to be the sole MCA family member in the rice genome. OsMCA1 functionally complemented a yeast mutant defective in the Mid1 gene encoding a putative Ca²⁺-permeable mechanosensitive channel component. To investigate its physiological functions, we developed transgenic plants as well as suspension-cultured cells in which its expression is enhanced or repressed. Ca²⁺ mobilization induced by various stress have also been characterized using apoaequorin-expressing lines. Possible roles of OsMCA1 in stress-induced Ca²⁺ influx will be discussed.