Figure 3.

Localization of BASL.

BASL acts as a molecular signal instructing stomatal lineage cells to divide away from it. BASL protein appears initially in the nuclei of meristemoid mother cells (MMC), which differentiate from protodermal cells. The protein then localizes in a second location at the cell periphery opposite the site of the future asymmetric division. Following that division, BASL remains at the cell periphery but fades away from the nucleus of the larger daughter cell (SLGC), which loses stomatal lineage identity; it remains in the nucleus of the meristemoid (M), which may further asymmetrically divide. BASL is not found in later stomatal lineage cells, such as (GMCs or GCs. However, when satellite meristemoids are formed by SLGCs that resume stomatal lineage fate, BASL appears at the SLGC periphery next to the stomatal lineage cell, providing a mechanism for maintenance of the one-cell spacing rule. (Based on data presented in Dong et al. [2009].)