A gateway with a guard: How the endodermis regulates growth through hormone signaling

• I provide an overview of areas of plant–environment response that we have a poor understanding of.
• I describe recent work on the function of the casparian strip.
• The role of the endodermis in Gibberellic Acid, Abscisic Acid and Strigalactone signaling is detailed in full.
• A discussion of polar auxin transport and PIN3 function in the endodermis is described.

The endodermis is a defining feature of plant roots and is most widely studied as a differentially permeable barrier limiting solute uptake from the soil into the vascular stream. Recent work has revealed that this inner cell layer is also an important signaling center for hormone-mediated control of growth. Auxin, gibberellic acid, abscisic acid and strigalactones all appear to depend on the endodermis to regulate root biology and point to this cell type as having important inter-cell layer regulatory activity, as well. In this review I discuss recent work detailing the importance of the endodermis in growth control and how this function is affected during responses to the environment.