Movement and functions of signaling molecules in the apoplast(<Feature Articles>The plant cell wall as an information processing system)

Abstract

The apoplast is the space outside the plasma membrane, consisting of the cell wall and its outer space. The apoplastic solution contains a wide variety of small molecules, some of which are taken up from soil with water. In addition, some chemicals biosynthesized in the cell are secreted into the apoplastic region through the plasma membrane. Xylem sap contains many of these small chemicals including signaling molecules, thus the apoplastic region has an important role in the translocation of these small signaling molecules. In this review, we describe recent topics on the movement and functions of selected hormonal molecules that are transported over a long distance through the xylem. In a broad sense, the long distance translocation of signaling molecules through the apoplast can be considered as a part of "the information processing system of the plant cell wall".