Expression of Arabidopsis TOL genes.

A strict control of abundance and localization of plasma membrane proteins is essential for plants to be able to respond quickly and accurately to a changing environment. The proteins responsible for the initial recognition and concentration of ubiquitinated plasma membrane proteins destined for degradation, are well characterized in mammals and yeast, (1) yet no clear orthologs were found in plants. (2) Recently, we have identified a family of proteins in higher plants, which function in vacuolar targeting and subsequent degradation of ubiquitinated plasma membrane proteins (3,4) termed TOM1-like (TOL) proteins.