In one of the first applications of atomic force microscopy to the study of tissue and cell mechanics in development, a team of scientists from France and Switzerland linked the changes in cell wall mechanics and chemical modifications of the cell wall structure to organ emergence and patterning.

This research was the outcome of an integrative approach involving biologists and physicists. The study results were published online on Oct 6 in the professional journal Current Biology.

Rigidity map of a living Arabidopsis shoot apical meristem. Image provided to ScienceDebate.com by Dr. Alexis Peaucelle.

The shoot apical meristem comprises a group of stem cells at the plant apex, where all aerial organs are formed- every leaf and flower is made during the life of the plant from the apical meristem. The organs are not randomly placed about the stem, but instead are patterned in their placement. This process is patterned by the differential distribution of the phytohormone auxin. The emergence of a new organ requires highly localized and coordinated cell expansion. In plant cells, cell expansion is majorly controlled by the cell wall which acts as a physical barrier to limit or permit expansion; for an organ to form it is expected that the cell walls of involved cells must become 'permissive' and this should involve changes in the physical/mechanical properties of the cell walls.

The authors of this study used atomic force microscopy to probe the mechanical properties of cell wall material at the apical meristem. Their results led to the development of a combined mechanical and biochemical model of organ formation in plants: the chemical modification of cell wall pectins leads to localized softening of the tissue, occurring first in subepidermal layers. Wall softening in subepidermal tissues would allow these tissues to expand causing the surface to bulge- initiating a new organ.

This technique, in one of the first applications of atomic force microscopy to the study of tissue and cell mechanics in development, has allowed the examination and reformulation of two major concepts regarding organ formation; it also highlights the importance of direct mechanical observations in understanding the mechanisms of development. “Given our findings, we believe that this technique will soon become the standard approach for studying the mechanics of development,” said the authors.