Functional characterization of Ca²⁺-permeable, stretch-activated ion channel candidates of Arabidopsis using yeast

Abstract

Arabidopsis MCA1 and MCA2 genes (formerly AtMID1A and AtMID1B, respectively) complement the lethality of the yeast mid1 mutant defective in a putative stretch-activated channel component (2004 JSPP meeting). By the two-phase agar method we developed, we have found that the root of an mca1-null mutant is incapable of sensing the hardness of agar (2006 JSPP meeting). Here, we performed the functional characterization of Mca1 and Mca2 in yeast. Mca1 was found to be localized in the plasma membrane as an integral membrane protein. Since yeast Mid1 must cooperate with yeast Cch1 to function as a high-affinity Ca²⁺ channel, Mid1 alone cannot complement the lethality of the mid1 cch1 double mutant. By contrast, Mca1 and Mca2 complemented individually the lethality of the double mutant and enhanced Ca²⁺ accumulation. The results suggest that Mca1 and Mca2 function as a Ca²⁺-permeable channel component whose action mechanism is different from that of Mid1.