​Solveig Plomer from the statistics group of Gaby Schneider (Goethe University) defended her thesis in the end of 2024. Within the LOEWE Schwerpunkt CMMS - Multiscale Modelling in Life Sciences she researched the movement of cell organelles in cooperation with Theresa Ernst and Philipp Gebhart from the group of Molecular Cell Biology of Plants and defined a new model for the description of cell organelle movement as well as a test and change point detection algorithm for changes in the model parameters.

The description of movement patterns can be important for the understanding of various biological processes on multiple scales. One of the primary goals is to understand the causes of change between movement patterns. On the micro scale, movement patterns of cell organelles and swimming microorganisms such as cells are investigated. To gain more insight into the different movement types of cell organelles, as well as the changes between these types, Plomer analyzed the movement of two specific types of cell organelles in the root of the plant Arabidopsis thaliana, plastids and peroxisomes.
In this data set of organelle movement visually prominent, linear movement structures with seemingly piecewise constant movement direction and speed are observed. Since the different sections of the movement could be associated with different movement mechanisms such as movement through cytoplasmic streaming or transport along intracellular filaments, it is of interest to detect change points in the direction and speed of the movement. In her thesis Solveig Plomer discusses Random walk (RW) models in the context of the organelle movement data set, suggesting that modeling absolute movement direction within a biased RW can be advantageous as compared to relative direction as assumed in the widely used correlated RWs. She proposes a new stochastic model called linear walk that describes movement along linear structures with piecewise constant movement direction and speed. In addition, maximum likelihood estimators and proof of their strong consistency are provided. In order to test for and estimate change points in the linear walk model on multiple time scales a moving kernel estimator is proposed as well as a graphical technique to distinguish between change points in movement direction and speed.
Solveig Plomer will work in specialized consulting starting April 2025.

Publications:
Solveig Plomer, 2024. Bivariate change point detection in direction and speed of cell organelle movement. Universitätsbibliothek Johann Christian Senckenberg, Frankfurt am Main. https://doi.org/10.21248/gups.88209 

Solveig Plomer, Theresa Ernst, Philipp Gebhardt, Enrico Schleiff, Ralph Neininger and Gaby Schneider, 2024. Bivariate change point detection in movement direction and speed. arXiv preprint arXiv:2402.02489. Submitted for publication.

Solveig Plomer, Annika Meyer, Philipp Gebhardt, Theresa Ernst, Enrico Schleiff and Gaby Schneider, 2024. Absolute direction in organelle movement. Ecology and Evolution, 14(8)

Solveig Plomer, Theresa Ernst, Philipp Gebhardt, Enrico Schleiff and Gaby Schneider, 2024. Plastid and peroxisome movement tracks in the root cells of arabidopsis thaliana [Dataset]. https://doi.org/10.5061/dryad.5hqbzkhfd