The physical properties that shape plant cells

Madeline Seale explains her groups interdiciplinary approach to plant cell research for the Trinity Term 2021 Alumni Newsletter.

As scientific research becomes ever more specialised, it can be easy to forget that our disciplinary distinctions are somewhat artificial. This is nothing new of course: 71 years ago Agnes Arber, the first female botanist elected to the Royal Society, wrote:

‘The aims which [the different branches of biology] pursue, and the highly technical methods by which these aims are achieved, differ so widely that one reminds oneself, with something of a shock, that all the branches are concerned with the same living world’ Agnes Arber (1950) The Natural Philosophy of Plant Form.

So once again, it pays to remind ourselves that biological organisms live in a world that is simultaneously influenced by rules of chemistry, mathematics, physics and other disciplines. My research concerns the shape, structure and function of plant cells and tissues, or as Arber would say more holistically ‘form’. Mathematics can help us describe cell shape that arises from the biological genes that influence growth and development, the chemical composition of the carbohydrates and proteins in the cell wall, and the physical forces conferred by water that inflates and pressurizes plant cells to provide turgor.

We are interested in how the water content of plant cells influences physical and material properties of plant cell walls. In their healthy hydrated state, plant cells experience internal turgor pressure comparable to a car tyre meaning that the cell wall is not only strong enough to withstand this, but is also under considerable tension. During drought, the tensile forces reduce as water is lost and compressive forces can cause collapse and damage to cell walls.

The cell wall itself is thought to contain around 40% of the cell’s water, to maintain spacing between fibres within the wall and keep the gel-like components elastic and compliant. Beyond this, the hydration of the cell wall has not been well studied and it is unclear how it’s water status impacts on cell wall integrity and broader processes of growth and stress responses. We aim to understand how plants respond to changing physical forces and how they adapt their cell walls to maintain their structure.

Together with David Vaux in the Dunn School of Pathology, we have been using newly-developed viscosity probes that localise to the plant cell wall to understand more about the physical properties of cell walls. These fluorescent dyes contain a molecular rotor that rotates more or less depending on the viscosity or molecular crowding of the environment, which then alters their ability to fluoresce.

Using these probes, we have been able to visualise, for the first time, large differences in viscosity of the cell wall during dehydration of moss cells. We are investigating how these physical changes in the cell wall impact on signalling and communication within the cell to respond to stress. This will help us to understand how plants use genetic mechanisms to process and integrate information about their physical surroundings.