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. 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.

Radial askew endodermal cell divisions reveal IRK functions in division orientation

“…There is increasing evidence, particularly from the stomatal development literature, that polarity domains with a cell can directly and/or indirectly position these structures via linkage with the cytoskeleton. For example, the BASL/BRX family polarity domain depletes cortical microtubules at particular positions to ensure the preprophase band forms outside the site marked by the polarity domain (Muroyama et al, 2022). Additionally, the trm6,7,8 triple mutant, which does not form preprophase bands, exhibits minor root cell division defects and fails to pattern stomata correctly as the links between cell polarity and division orientation are disrupted (Schaefer et al, 2017).…”

Spatially resolved proteomics of the stomatal lineage: polarity complexes for cell divisions and stomatal pores

“…The placement of the division plane and new wall is prefigured by the preprophase band of microtubules, and we hypothesized that the OPL2 patches could serve as guideposts to reorient the preprophase band along the long cell axis in GMCs. To enable high-resolution imaging of OPL2 and preprophase bands during the GMC division, we created lines co-expressing microtubule marker TMMp:mCherry-TUA5 [24] and OPL2 driven by strong and GMC/GC-specific FAMA promoter [25] (FAMAp:OPL2-VENUS). Indeed, OPL2-VENUS polar patch formation in GMCs coincided with preprophase band microtubule formation (Figure S1A-A').…”

“…The co-localization of OPL2 and microtubules is especially relevant because of the recent discovery that the oppositely polarized BASL/BRXL2 complex orients division planes during ACDs by creating a zone that excludes stable preprophase band and interphase cortical microtubules [24]. We tested whether OPL2 and BRXL2 maintained their opposite polar localization and relationship to microtubules during symmetric GMC divisions; indeed, they do (Figure 2A-G) with OPL2 occupying the ventral and BRXL2 the dorsal ("outer") domains of the newly divided cell pair (Figure 2C-C').…”

“…BASL, BRX family and POLAR are intrinsically disordered and each serves as a scaffold for a different intracellular signaling cascade [5,8] [6]. Nuclear migration and destabilization of microtubules within the BASL-BRX domain orients the division plane away from the polar domain to ensure asymmetry of the division [9,10]. After ACD, the larger SLGC daughter therefore inherits the BASL-POLAR-BRX polarity domain including the scaffolded effectors, whereas the smaller meristemoid daughter does not, leading to the two daughters acquiring different fates [5,6,8].…”

De NovoTANGLED1 Recruitment to Aberrant Cell Plate Fusion Sites in Maize

“…Genetic disruption of PPB formation often leads to significantly stunted growth and division plane positioning defects (Torres-Ruiz and Jürgens, 1994;Camilleri et al, 2002;Kawamura et al, 2006;Azimzadeh et al, 2008;Wright, Gallagher and Smith, 2009;Drevensek et al, 2012;Kirik, Ehrhardt and Kirik, 2012;Spinner et al, 2013;Kumari et al, 2021;Muroyama et al, 2023). Often, mutants with defects in PPB formation also have disrupted cortical microtubule organization, which may impede cell expansion (Torres-Ruiz and Jürgens, 1994;Whittington et al, 2001).…”