MYB68 regulates suberin patterning and radially distinct endodermal differentiation

Abstract

Roots are composed of concentric tissue layers that enable selective uptake of nutrients, attributed to the vascular-embracing endodermis. In mature root regions, endodermal cells coat their cell surface in a hydrophobic polymer termed suberin, which blocks solute transport across the plasma membrane. Intriguingly, specific cells adjacent to the water-conducting xylem remain unsuberized. These are termed passage cells based on the assumption that they create a passage for nutrient influx into vasculature in the otherwise sealed-off root regions. The identity and function of passage cells remain unknown, but their presence proposes the existence of individual identities within the endodermis. In this study, we probe this by performing an in-depth investigation of passage cells and endodermal suberization in the model plant Arabidopsis thaliana. Our work identifies the transcription factor MYB68 as a key regulator of suberization and endodermal lineage-specification related to passage cell formation. Through transcriptional profiling of myb68 mutants, we unravel genes with passage cell-associated expression that suggest a function in cation homeostasis. Collectively, our findings create a framework for a deeper understanding of radial cell identities within the endodermis and highlight that dynamic spatiotemporal patterning is an important physiological feature of root ground tissues.