Apoplastic Signalling Communicates Emergency Responses

In order to survive, organisms must interpret diverse signals across all scales of biological organisation - from individual cells to tissues and the whole organism. Only by doing so can they withstand environmental heterogeneity and stress.

In multicellular organisms, a key component of stress responses is the exchange of information between cells and tissues to co-ordinate responses across the whole organism. This is common in multicellular life, but different kingdoms display diversity in mechanisms for signal transmission.

For example, while animals have a central nervous system for rapid signal transmission, plants also transmit information rapidly through the body despite lacking a brain and nerve cells.

How plants transmit signals so rapidly has been a focus of significant debate over the last century, with increasingly complex and conflicting models proposed to explain this phenomenon in plants.

We recently discovered that rapid, systemic calcium waves travel through plants via flow and diffusion of amino acids through the extracellular domain of the plant body.

This discovery aligns with models of long-distance signalling in plants proposed a century ago, but conflicts with present day models, and leads us to ask whether diffusion and flow, and other passive mechanisms, can explain signal transmission in a variety of responses.

Thus, I hypothesise that a wide array of small molecules and peptides are released from cells during stress and travel through the extracellular apoplast, transmitting information to surrounding naïve cells and tissues.

In this project I propose that these molecules travel via passive mechanisms and therefore that the nature of a chemical messenger, its mechanism of transmission, and the route it travels, define the spatial and temporal profile of an overall response.

We will test this hypothesis to establish a simple framework for using measurable parameters of a system to predict signal transmission and complex response profiles.