The importance of being edgy: cell geometric edges as an emerging polar domain in plant cells

Abstract

Summary Polarity is an essential feature of multicellular organisms and underpins growth and development as well as physiological functions. In polyhedral plant cells, polar domains at different faces have been studied in detail. In recent years, cell edges (where two faces meet) have emerged as discrete spatial domains with distinct biochemical identities. Here, we review and discuss recent advances in our understanding of cell edges as functional polar domains in plant cells and other organisms, highlighting conceptual parallels and open questions regarding edge polarity.

A coupled mechano-biochemical model for cell polarity guided anisotropic root growth

“…PIN sensitivity of each membrane varies between 0 and 1 and the total PIN sensitivity of all membranes sections sum up to 1. PIN sensitivity is the linear combination of auxin flow (defined either by auxin flux or auxin concentrations), growth anisotropy (defined by AF), and lesser extent the cell geometry ( Elliott and Kirchhelle, 2020 ). Columella cells are the only exception to this rule; in the columella, PINs are always trafficked uniformly among membrane sections to reflect the observed PIN3 distribution ( Friml et al, 2002 ).…”

Cytoskeletal regulation of primary plant cell wall assembly

“…Examples are the formation of Hechtian strands -where the plasma membrane stays attached to the cell wall at certain locations but easily detaches in other regions -and the highly polar distribution of cell wall assembly in tip-growing cells 26 . Precise spatial domain identity is also required to control cell behavior at cell edges 35 or selected cell faces 36 . Targeted delivery ensures the local enrichment of a given molecular player, but what controls and confines the spatial distribution and lateral movement of plasma-membranelocated proteins once inserted at the target site at the cell surface?…”

Spatio-temporal control of post-Golgi exocytic trafficking in plants

“…Subcellular localisation can also be associated with physiological responses; for example, in stomatal guard cells, the endoplasmic reticulum (ER) is predominantly located in the connecting region where two guard cells meet when stomata are closed, but relocalises to the dorsal cell side when stomata opena pattern not observed for other endomembrane organelles (Higaki et al, 2012). Polarised trafficking is particularly prevalent during growth, where different regions of cells grow at vastly different rates and cells display elaborate biochemical polarisation (reviewed by Elliott and Kirchhelle, 2019;Nakamura and Grebe, 2018). Polarised trafficking is also a prominent feature during pathogen infection and subsequent immune responses, which involve trafficking to and from discretely localised infection sites (reviewed by Rivero et al, 2019).…”