Functional Characterization of a Ca²⁺-permeable, Stretch-activated Channel Candidate In Arabidopsis

Abstract

The Ca²⁺-permeable, stretch-activated (SA) channel is regarded as a mechanosensor. We have isolated Arabidopsis genes encoding SA channel candidates designated AtMID1A and AtMID1B that can complement the yeast mid1 mutant (2004 JSPP meeting). We examined whether AtMid1A and AtMid1B are involved in touch perception in roots. A significant population of atmid1a and atmida atmid1b roots could not enter the harder medium from the softer medium of the two-phase agar medium, whereas wild-type and atmid1b roots were able to do so. The Ca²⁺ uptake activity of the roots of the AtMID1A-overexpressor was higher than that of wild-type roots. In addition, this activity was inhibited by the SA channel blocker Gd³⁺-, but not by the voltage-gated Ca²⁺ channel blocker verapamil. These results suggest that AtMid1A is an SA channel component required for touch sensing and Ca²⁺ uptake in roots.