Cortical polarity ensures its own asymmetric inheritance in the stomatal lineage to pattern the leaf surface

Abstract

Asymmetric cell divisions (ACDs) specify differential cell fates across kingdoms. In metazoans, preferential inheritance of fate determinants into one daughter cell frequently depends on polarity-cytoskeleton interactions (1, 2). Despite the prevalence of ACDs during plant development, evidence for analogous mechanisms that segregate fate determinants during ACD remain elusive. Here, we describe a mechanism in the Arabidopsis thaliana leaf epidermis that ensures unequal inheritance of a fate-enforcing polarity domain during the creation of stomata, essential two-celled valves that mediate gas exchange between the plant and environment. Formation of a plasma membrane-associated polarity domain, defined by BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL), overrides default division patterns in stomatal precursors. The polarity domain exerts this control by constraining formation of the preprophase band of microtubules that mark the cortical division site and are a hallmark of plant mitosis. Experimentally uncoupling preprophase band establishment from the polarity domain results in aberrant polarity inheritance and subsequent fate errors. Mechanistically, our analyses of the interactions between microtubules and BASL in native and heterologous contexts revealed that the stomatal lineage polarity domain locally depletes cortical microtubules by altering microtubule stability. As the inherited cortical BASL crescent scaffolds a MAPK cascade to suppress progenitor identity in one daughter post-division, we propose that BASL-microtubule interactions represent a novel strategy to link cell identity to division orientation. Together, our data highlight how a common biological module, coupling the cytoskeleton to fate segregation via cell polarity, has been configured to accommodate the unique features of plant development.