Abstract
The root tip senses the hardness of the soil to decide the direction of root elongation. The Ca2+-permeable mechanosensitive channel is postulated to be a key element of touch sensing at the root tip. Recently, we have reported candidates for such channels, named MCA1 and MCA2, both of which share 73% amino acid sequence identity (Nakagawa et al., PNAS 104:3639-3644, 2007). In this report, we have shown that the primary root of mca1 plants cannot enter the lower, harder agar medium from the upper, softer agar medium. Here, we show that the primary root of mca2 plants can enter the lower, harder agar medium, like that of wild-type plants. Interestingly, this phenotypic difference between the two mutant plants may be explained by the results of GUS staining. Namely, MCA1p::GUS was found to be expressed in the root apical meristem, while MCA2p::GUS was not.
