The Casparian strip—one ring to bring cell biology to lignification?

[Display omitted] •Endodermal Casparian strips are a model for spatially controlled lignification.•Scaffold proteins and enzymes ensure spatially precise ROS production and consumption.•Dirigent proteins are involved in Casparian strip formation.•Defects in Casparian strip lead to compensatory lignification.•Compensatory lignification differs from Casparian strip lignification. Lignin research has long been motivated by the outstanding importance of wood for human societies. The annual, non-woody Arabidopsis thaliana, has nevertheless contributed greatly to our understanding of lignification, due to its unrivalled genetic resources. Arabidopsis is also great for cell and developmental biology, allowing precise imaging and tracking of cell types. Root endodermis differentiation involves the precise lignification of the Casparian Strip, as an apoplastic barrier; while barrier damage triggers a less localized, compensatory lignification. Transcriptional reprogramming and peptide-induced signalling emerge as promising tools for the study of endodermal lignification. We argue that endodermis lignification is an attractive model complementary to equally powerful, cellular xylem differentiation systems, as it might better represent the restricted – often localized – lignification seen in non-vascular cells.