Diffusible repression of cytokinin signaling produces endodermal symmetry and passage cells (Nature)

Passage cells are a subset of interspersed root endodermal cells that are unsuberized, which is thought to aid in transport because suberin inhibits transcellular transport. In Arabidopsis, suberization follows a stereotypic pattern which responds to many stress conditions, partly mediated by abscisic acid (ABA). Anderson et al. investigate the mechanism behind this patterning and the role suberin plays in transport of nutrients into the root. Suberin-lacking cells associated with the xylem pole and two xylem patterning mutants, cytokinin-related, displayed reduced numbers of passage cells. Cytokinin was mostly absent in unsuberized cells, and exogenous cytokinin application decreased passage cell numbers, as did ABA. On the other hand, cytokinin inhibition resulted in mostly passage-like endodermal cells that lacked suberization and this was not rescued by addition of ABA. Lastly, they identified passage cell-specific expression of transporters involved in nutrient uptake. This work expands upon the role and regulation of suberin in the endodermis as well as adding to the current model of nutrient uptake in plants. (Summary by Alecia Biel) Nature. 10.1038/nature25976.