Potassium deficiency reinforces the endodermal but not the exodermal suberized barrier in maize seminal roots

Potassium (K) deficiency imposes a constraint on maize production, and its impact on suberized apoplastic barriers, particularly in seminal roots, has been uncertain. To investigate this, researchers grew maize under K deficiency in soil and at varying K concentrations in hydroponic solutions, using ABA and fluridone treatments.

By analyzing seminal roots, they employed Fluorol Yellow 088 staining, tissue-resolved suberin chemistry, rubidium (Rb) flux, and RNA-sequencing with weighted gene co-expression network analysis (WGCNA).

The findings reveal that K deficiency selectively increases endodermal aliphatic suberin and eliminates endodermal passage cells in soil-grown roots, while exodermal suberin remains unchanged. Despite high K influx, root-to-shoot Rb translocation dropped significantly, indicating K retention. This suggests a connection between the suberin biosynthetic genes and several K transport genes, with the suberin program responding to exogenous ABA, demonstrating ABA-dependent co-regulation.

Both soil and hydroponic systems resulted in the same endodermis-specific anatomical response. The endodermal barrier, but not the exodermal barrier, was reinforced, limiting K leakage from the stele in maize roots. This tissue-specific plasticity points to the endodermal suberin biosynthesis program and its coordination with K uptake as a target for enhancing K use efficiency in maize.