Dynamics of Self-Organized Organelle Transport in a Developing Macroscopic Single-Celled Organism*

Caulerpa is a marine green alga exhibiting differentiated organs resembling leaves, stems and roots; while individuals can exceed a meter in size, each one is comprised of a single multinucleated giant cell. Thus, according to current understanding, the distinction between the cellular and organismal levels in Caulerpa does not exist. In turn, this challenges our intuition that morphogenesis on large scales necessitates division into cells.
It has been hypothesized that active transport plays a key role in the development of the alga. Yet, the most recent reports studying organelle transport in Caulerpa are over three decades old.
We have designed an imaging system based on the affordable Raspberry-Pi and its camera module. The system allows us to track over weeks the morphogenesis of tens of samples in parallel, each one in a separate well. Our observations of chloroplasts redistribution on whole-organism scales over hours reveal a pulse-like behavior. We further explore this macroscopic manifestation of the self-organized transport through perturbations, such as alternating illumination protocols and application of an external electric field. In this work we seek to establish a framework to study the dynamics of homeostasis and its stability.