Figure 2.

Proteins that polarize relative to the major plant body axes. A, In a longitudinal section of the root, NIP5;1 and PEN3 localize to the outer domain, while BOR1 and BOR2 localize to the inner domain. In the endodermis, IRK and SGN1 localize to the outer domain, and SGN3 is found in the apical and basal domains. B, In a transverse section of the root, SGN3 localizes to the circumferential domain of endodermal cells where neighboring cells of the same tissue layer meet. SGN1 localizes to the outer domain. C, In root protophloem cells, OPS localizes to the apical domain, while BRX and PAX localize to the basal domain. D, SOK1 is natively expressed in vascular cells, where it localizes to the apical outer corner. SOK2 is natively expressed in the endodermis, where it localizes to the basal inner corner. When ectopically expressed, SOK2 maintains the same polar localization in all cell layers. In contrast, although SOK1 remains apical in all cell layers, its distribution along the inner–outer axis is oriented toward the cortex-endodermis junction. Root tissues in (A)–(D) are color-coded as indicated in Figure 1. E, Ectopically expressed BASL throughout the leaf localizes to a single lobe of pavement cells aligned with the proximal–distal axis. F, Polar distribution of NIP5;1 to the outer domain and BOR1 to the inner domain in the eight-cell stage embryo.