Identity is Everything : MYB68 regulates endodermal differentiation and suberin patterning

Root cells are organized into concentric layers that facilitate the movement of water and nutrients. Among these, the endodermis overlays the root vasculature, allowing it to play a major role in selective uptake. To perform this function, endodermal cells undergo two distinct stages of differentiation. The first stage involves the formation of the Casparian strip barrier that prevents extracellular diffusion, while the second leads to the deposition of suberin, a hydrophobic polymer that seals off the vasculature. However, some endodermal cells are not suberized, forming patchy zones in the barrier known as passage cells, which are hypothesized to provide low-resistance routes for selective uptake. In Arabidopsis, the central vasculature is arranged in opposing poles of xylem and phloem, and to function effectively, endodermal cells align with one of three positional identities: xylem pole-associated (XPE), phloem pole-associated (PPE), or non-pole-associated (NPE). In this study, Kraska et al. identified a MYB-class transcription factor, MYB68, as a regulator of suberin patterning in XPE and NPE cell files. MYB68 knockout lines showed reduced suberization frequency in both XPE and NPE files, alongside expanded patchy zones in XPE files. Despite these spatial disruptions, the onset of suberization and the overall patterning rate remained comparable to wild type, suggesting that MYB68 functions within an age-dependent regulatory network rather than initiating suberization. To further investigate MYB68’s role in suberin patterning, the authors used a transcriptional marker for a gene typically expressed in passage cells and observed a significant increase in expression in the mutants, indicating that MYB68 represses passage cell identity. This work lays the foundation for decoding the genetic network that patterns endodermal cell identity and suberization. (Summary by Irene I. Ikiriko @ireneikiriko) Cell Reports 10.1016/j.celrep.2025.115794