Molecular characterization of Arabidopsis Ca²⁺-permeable mechanosensitive channel candidates using yeast

Abstract

To investigate the mechanism of mechanosensing in plants, we have isolated genes of Ca²⁺-permeable mechanosensitive channel candidates from Arabidopsis thaliana, MCA1 and MCA2 (Nakagawa et al. , PNAS 104:3639-3644, 2007). Mca1 and Mca2 have 73 % identity in amino acid sequence and can complement the lethality of the yeast mid1 mutant, although sequence similarity between Mca1/Mca2 and Mid1 is low. Mca1 and Mca2 possess a regulatory domain of rice putative protein kinases, an EF-hand-like motif, and a coiled-coil motif in the N-half and transmembrane segments and a Cys-rich domain in the C-half. We have found that Mca1 is involved in Ca²⁺ influx and touch sensing in roots. Here, we performed molecular characterization of Mca1/Mca2 using yeast. We found that Mca1/Mca2 could form a dimer and a tetramer and that the C-half of Mca1 expressed in yeast did not retain Ca²⁺ uptake activity and the N-half was lethal to yeast.