Skip to main content
Doctoral thesis, 2018

Role of the cell wall in cell shape acquisition

Majda, Mateusz

Abstract

The growth and development of an organism depend on the coordinated expansion and shape acquisition of individual cells. The epidermis, primarily controls morphogenesis as well as acts as an essential component at the interface with the environment. In plants, the cell wall, a polysaccharide network located outside the plasma membrane, ensures tight junctions between cells and determines the expansion rate and direction of each neighbouring cell, thereby determining cell shape and tissue morphology. Interestingly, plant cells are characterized by a great diversity of shapes, which vary from simple isodiametric forms to more complex structures such as in the puzzle-shaped pavement cells (PCs), displaying alternating lobes and necks, which are observed in the leaf epidermis. In our studies, we investigated the role of wall composition and mechanical properties in cell shape acquisition. We found that in Arabidopsis thaliana, cell wall integrity is essential for proper PC shape formation and that the mechanical properties of the cell wall between two mature PCs are heterogeneous. Further detailed examinations revealed the existence of a stiffness gradient across the curved cell wall at the lobes. We then showed that locally softer regions display an increased accumulation of specific pectic components such as galactans and arabinans, demonstrating their role in the regulation of wall mechanical properties. Furthermore, the appearance of these local heterogeneities precedes the cell morphological changes, indicating that the wall modifications are needed to initiate the lobing process. The cell wall composition was also studied in another species, Cinnamomum camphora (camphor tree), revealing a polarization of some cell wall components in PCs, and, uniquely, the presence of wall lignification in both epidermal and mesophyll cells. We also demonstrated that PC division pattern and development are correlated with an auxin gradient generated by directional transport, making a direct link with what is known on auxin stimulated acid growth and transcriptional response of genes controlling cell wall biosynthesis and remodelling. Altogether, our results support a major role for plant cell walls in cell shape acquisition. Our data reveal a striking dynamicity of PC cell walls, displaying the polarly distributed mechano-chemical properties required for lobing, which change according to the cell developmental stage. Furthermore, our work tightly links the master growth regulator auxin to the regulation of cell shape via a complex and dynamic control of cell wall remodelling.

Keywords

epidermis, pavement cells, cell walls, mechanics, auxin, polarity, pectins, galactan, arabinan, xylan, lignin, arabidopsis, camphor tree

Published in

Acta Universitatis Agriculturae Sueciae
2018, number: 2018:10
ISBN: 978-91-7760-160-9, eISBN: 978-91-7760-161-6
Publisher: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences.

Authors' information

Majda, Mateusz
Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology

UKÄ Subject classification

Biochemistry and Molecular Biology
Biophysics
Cell Biology

URI (permanent link to this page)

https://res.slu.se/id/publ/104171