Quantitative and dynamic cell polarity tracking in plant cells

Abstract

Quantitative information on the spatiotemporal distribution of polarized proteins is central for understanding cell-fate determination, yet collecting sufficient data for statistical analysis is difficult to accomplish with manual measurements. Here we present POME, a semi-automated pipeline for the quantification of cell polarity, and demonstrate its application to a variety of developmental contexts. POME analysis reveals that during asymmetric cell divisions in the Arabidopsis thaliana stomatal lineage, polarity proteins BASL and BRXL2 are more asynchronous and less mutually dependent than previously thought. While their interaction is important to maintain their polar localization and recruit other effectors to regulate asymmetric cell divisions, BRXL2 polarization precedes that of BASL and can be initiated in BASLs absence. Uncoupling of polarization from BASL activity is also seen in Brachypodium distachyon, where we find that the MAPKKK BdYDA1 is segregated and polarized following asymmetric division. Our results demonstrate that POME is a versatile tool, which by itself or combined with tissue-level studies and advanced microscopy techniques can help uncover new mechanisms of cell polarity.