Figure 9.

A possible model of the function of FAB1 and its product PtdIns(3,5)P₂ on late endosome maturation in young root cortical and stele cells in Arabidopsis. PIN proteins are recycled via the TGN/EE and FAB1/SNX1-positive endosomes to the basal PM in young root cortical and stele cells. Mature FAB1/SNX1-positive endosomes are partly attached and move along cortical microtubules with late endosomal effector proteins and microtubule-associated proteins. If the FAB1 function is compromised, the late endosomal effector proteins could not be accumulated due to the lack of the scaffold molecule, PtdIns(3,5)P₂; consequently, endosome maturation is inhibited at the early stage of the process.