The Arabidopsis SUBERMAN is a Component of the Regulatory Network Establishing Root Endodermis Suberization

Root endodermis, the innermost cortical layer surrounding the root vasculature, serves as the foremost barrier to water, solutes, and nutrients taken up from soil. Endodermis barrier functionality is achieved via its hydrophobic coating of lignified Casparian strips and the suberin lamellae; nonetheless the regulatory mechanisms underlying endodermis suberization are still elusive. Here, we discovered that the Arabidopsis SUBERMAN (SUB) transcription factor controls establishment of the root suberin lamellae. We show that SUB activates suberin gene promoters. In Arabidopsis, SUB is expressed in root endodermis cells, and thus roots with higher or lower expression of SUB display altered suberin polymer deposition patterns and modified composition. While these changes did not interfere with Casparian strip formation they had a substantial effect on root uptake capacity resulting in varied root and leaf ionomic phenotypes. Gene expression profiling revealed that SUB function impacts suberin, phenylpropanoids, lignin and cuticular lipids biosynthesis as well as root transport activities, hormone signaling and cell wall modification. We moreover revealed that SUB acts downstream of the SHORTROOT-SCARECROW-MYB36 regulatory network that promotes endodermis differentiation albeit not being controlled directly by these factors. Overall, our findings highlight SUB as a novel regulator of developmental endodermis suberization in the Arabidopsis root.