Agent Based Modelling of Auxin Transport Canalisation

The transport of the plant hormone auxin is central to many aspects of plant development. This thesis describes work developing agent-based simulations of auxin transport canalisation. Auxin transport canalisation is the dominant
theory describing how auxin promotes its own transport through a tissue from a site of auxin biosynthesis to an auxin sink. Directional transport of auxin through plant tissues is mediated by the PIN family of membrane transporters. The exact mechanisms of PIN localisation that facilitate this directional transport are not known. Part of the aim of this work is to test theories of PIN localisation.

The development of the agent-based simulations has been assisted by the CoSMoS process. Using the CoSMoS modelling process, a series of models are produced that assist in the development of simulations of PIN localisation hypotheses. The CoSMoS process describes a systematic method for the
development of simulations of complex systems. The process helps to ensure that the assumptions made during the modelling process are understood, and known.

Two generations of simulator have been developed. The first has successfully tested two hypotheses of PIN localisation in rectangular cells. One, the Diligent Worker Hypothesis is able to produce auxin transport canals in tissues. These canals are an emergent property of the hypothesis and form in a variety of situations. The CoSMoS process was then used to enhance the existing model to test the Diligent Worker Hypothesis in irregular cells of a more natural shape, and to lay the foundation for a well constructed 3D model. The enhanced simulator is flexible and could be used in the future for the testing of additional localisation hypotheses, or auxin homoeostasis in cells.