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Abstract

Cell-cell adhesion is a fundamental requirement for multicellularity in plants, ensuring that cells remain connected despite the mechanical stress of turgor pressure and growth. Although adhesion has traditionally been attributed to the pectin-rich middle lamella (ML), growing evidence suggests that this view is overly simplistic. In this thesis, I investigated structural, molecular and developmental aspects of adhesion in Arabidopsis thaliana. In Paper I, finite element modelling and advanced microscopy demonstrated that outer epidermal edges are hotspots for cell-separating tensile stress, where we uncovered supracellular reinforcement points; the supracellular outer epidermal wall (SOEW) and the outer epidermal edge filling (OEEF) that function as load-bearing ultrastructural features that prevent separation, In Paper II, I showed that sucrose metabolism is one of the regulators of cell-cell adhesion maintenance. Exogenous sucrose intensified adhesion defects in multiple mutans and surprisingly induced “micro-cell adhesion defects” in wild type. These defects corelated with changes in tissue mechanics, radial expansion and cell shape anisotropy, in part likely linked to microtubules dynamics, identifying sugar metabolism as a regulator of cell adhesion. In Paper III, we investigated how cell wall integrity, particularly pectin biosynthesis, influences apical hook development. Mutants defective in homogalacturonan (qua2, gae1gae6, mur1), which display adhesion defects, failed to form a proper apical hook. In qua2, these defects correlated with loss of auxin asymmetry, reduced expression of HLS1 and PIF4 and altered GA metabolism, opening new avenues to explore how adhesion and wall integrity connect to hormonal signalling. Together, these studies open the door to new questions about how adhesion reinforcement points are established and maintained through regulatory and feedback mechanisms to ensure supracellular integrity in multicellular organisms.

Keywords

Adhesion; cell wall; ultrastructure; middle lamella; edges; cellulose; sucrose; cell wall integrity; apical hook

Published in

Acta Universitatis Agriculturae Sueciae
2025, number: 2025:67
Publisher: Swedish University of Agricultural Sciences

SLU Authors

UKÄ Subject classification

Botany
Cell Biology

Publication identifier

  • DOI: https://doi.org/10.54612/a.1f5ikdvchu
  • ISBN: 978-91-8124-051-1
  • eISBN: 978-91-8124-097-9

Permanent link to this page (URI)

https://res.slu.se/id/publ/142468