Endodermis-specific Receptor-like Kinase (ERK1) is required for the deposition of lignin in the Casparian strip in the root

The Casparian strip constitutes a physical diffusion barrier formed by the polar deposition of lignin in the root endodermis. The polar deposition of lignin is thought to be mediated by the scaffolding activity of membrane bound Casparian Strip domain proteins (CASPs) and the dirigent domain-containing protein Enhanced Suberin1 (ESB1). Here, we show that the endodermis-specific receptor-like kinase (ERK1), is part of this machinery, playing an essential role in the localization of CASP proteins and in the deposition of lignin, which ultimately are required for the formation of afunctional Casparian strip. ERK1 is localized to the cytoplasm and nucleus of the endodermis, and is part of a signalling pathway that implicates the circadian clock regulator Time for Coffee (TIC). In addition, we found that loss of ERK1 and TIC disrupts the Casparian strip organisation and alters composition of the root microbiome.