Dynamic patterns of the plant growth regulator auxin

• Applicant: Professorin Dr. Karen Alim
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 318879394

The most influential messenger during plant development is the tiny growth regulator auxin. The phytohormone controls basic processes like cell division and cell growth, and accumulates in patterns underlying the shoot architecture and the leaf vasculature. Thereby auxin controls the dynamic morphology of plants. The patterns of auxin and its carriers PIN and AUX/LAX are dynamic and reorganize throughout plant development. The long history of modelling auxin patterns has recently experienced a reset as the up to then mystical PIN polarity was uncovered to be likely coordinated by mechanical stresses arising within the developing tissue. This finding now suggests the following underexplored feedback cycle between auxin/PIN and tissue mechanics. High auxin concentration in a cell softens adjacent cell walls thereby generating mechanical stresses within the tissue. Mechanical stresses in return feed back on auxin flows as PIN binding is upregulated along stressed cell walls. As tissue mechanics plays a fundamental role in auxin patterning so does cell geometry and biomechanical variations across a tissue. How much cell geometry and biomechanical variation impact auxin patterning is an open question.To address this important question, we here propose to investigate the role of cell geometry and biomechanical variation on auxin patterning by predicting auxin patterning dynamics on segmented tissues from live imaging, and by comparing model predictions to experimental observations. In particular, we will use the natural variability in the auxin dynamics leading up to founder cell selection, marked by two adjacent cells with high auxin concentration, to identify the role of cell geometry in auxin patterning dynamics. Further, we will employ the pivotal and well-known mechanical changes of the overlaying endodermis during lateral root formation as a case study for the role of biomechanical variations across a tissue on auxin patterning. Both case studies will be performed in close feed back with experimental data from the Maizel lab (P6) and will further allow us to explore how cell divisions impact tissue mechanics and auxin patterning. Exploring the variation in cell geometry at the shoot apical meristem as investigated by the Lohmann lab (P5) will provide an independent tissue geometry to test for the impact on cell geometry on auxin patterning. The unprecedented close interaction of theoretical modelling and experimental observations will provide a new benchmark for auxin patterning dynamics and our understanding of how plant tissue mechanics and biochemical signalling are intertwined during plant development.

• DFG Programme: Research Units
• Subproject of: FOR 2581: Quantitative Morphodynamics of Plants