Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session G10: Quantitative Cell Physiology II - Metabolism and Growth
11:30 AM–2:30 PM,
Tuesday, March 7, 2023
Room: Room 202
Sponsoring
Unit:
DBIO
Chair: Terence Hwa, University of California, San Diego
Abstract: G10.00013 : Dynamical States of Self-Organised Waves in a Giant Single-Celled Organism Feeding on Light*
1:54 PM–2:06 PM
Presenter:
Eldad Afik
(Division of Biology and Biological Engineering, California Institute of Technology; Howard Hughes Medical Institute)
Authors:
Eldad Afik
(Division of Biology and Biological Engineering, California Institute of Technology; Howard Hughes Medical Institute)
Tony J Liu
(Division of Biology and Biological Engineering, California Institute of Technology)
Elliot M Meyerowitz
(Division of Biology and Biological Engineering, California Institute of Technology; Howard Hughes Medical Institute)
Caulerpa consists of differentiated organs resembling leaves, stems and roots. While an individual can exceed a meter in size, it is a single multinucleated giant cell. Active transport has been hypothesized to play a key role in organismal development; it has been an open question whether the rhythmic transport is of autonomous circadian nature. Using Raspberry-Pi cameras, we track over weeks the morphogenesis of tens of samples concurrently, while tracing at resolution of tens of seconds the variation of the green coverage. The latter reveals waves propagating over centimetres within few hours, and is attributed to chloroplast redistribution at whole-organism scale. By coarse-graining in space we achieve a reduced description to a dynamic macroscopic observable.
Our observations of algal segments regenerating under 12-hours-light / 12-hours-dark cycles show that the initiation of the waves precedes the external light change. The temporal-spectrum of the green pulses contains a circadian period; the latter persists over days even under constant illumination. Furthermore, we identify distinct dynamical states subject to the applied illumination protocol, as well as an effect on morphogenesis.
Time-keeping and synchronization are recurring themes in the research of Living Systems as contributors to Homeostasis — biological self-stabilization far-from-thermal-equilibrium, as well as to Anticipatory Behaviour. Studying this seemingly primitive light-fed Homeostatic System offers an opportunity to explore relations among biological oscillators, metabolism and morphogenesis.
*Howard Hughes Medical Institute
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