How do cells control the direction in which they grow? In addition to modifying cell wall properties at different faces of each cell, we identified geometric edges of cells (where two faces meet) as a crucial domain for growth directional control in lateral roots (Kirchhelle et al., 2016). Cells in these organs specify a trafficking pathway to the cell edges through the plant-specific small GTPase RAB-A5c. When function of RAB-A5c was inhibited though inducible expression of a dominant-negative protein variant RAB-A5cNI, cellular growth direction was severly perturbed, leading to defects in cell and organ morphology.
