In plants, coordination of cell division and differentiation is critical for tissue patterning and organdevelopment. Directional cell signaling and cell polarity have been proposed to participate in
coordination of these developmental processes. For instance, a leucine-rich repeat receptor-like
kinase (LRR-RLK) named INFLORESCENCE AND ROOT APICES KINASE (IRK) functions to
restrict stele area and inhibit longitudinal anticlinal divisions (LADs) in the endodermis where it is
polarly localized. The LRR-RLK most closely related to IRK is PXY/TDR CORRELATED 2
(PXC2) and we find that PXC2 shows similar polarized accumulation as IRK in root cell types.
To further understand how these proteins operate in directional cell-cell signaling and root
development we explored PXC2 function. pxc2 roots have an increase in stele area, indicating
that PXC2 also functions to restrict stele size. Additionally, compared to either single mutant, irk
pxc2 roots have an enhanced phenotype with further increases in endodermal LADs and stele
area indicating redundant activities of these receptors. The double mutant also exhibits
abnormal root growth, suggesting broader functions of PXC2 and IRK in the root. However,
PXC2 is not functionally equivalent to IRK, as endodermal misexpression of PXC2 did not fully
rescue irk. We propose that PXC2 is at least partially redundant to IRK with a more predominant
role for IRK in repression of endodermal LADs. Our results are consistent with the hypothesis
that repression of specific endodermal cell divisions and stele area through a PXC2/IRKmediated
directional signaling pathway is required for coordinated root growth and
development.