Unraveling Caulerpa’s Growth Mysteries: Insights into a Single-Cell Algae’s Development

Caulerpa, a unique type of marine algae, is a single extended cell but can expand to a meter in size. Unlike typical plants made of multiple cells with defined tasks, Caulerpa lacks cell membranes dividing it into individual cells. This results in an interconnected cytoplasm, raising questions for biologists about how it functions without separate cells.

Most multicellular organisms grow through cell differentiation, where distinct cells assume specific functions. However, Caulerpa’s growth challenges this norm. While specialized human organs develop from embryonic cell groups, Caulerpa’s single-celled structure raises queries about how it grows without cell specialization guiding it.

Eldad Afik, a postdoctoral scholar at Caltech, shares, “In Caulerpa, there’s nothing separating the nuclei. How does it create differentiated environments like organs in multicellular plants?” Their study, led by Afik under Elliot Meyerowitz at Caltech, reveals that Caulerpa follows an internal clock governed by the light cycle.

The research suggests that light triggers Caulerpa to release chloroplast waves throughout its body, aiding photosynthesis and growth. Caulerpa adapts to varying day and night durations, adjusting its behavior accordingly. The study lacks a clear understanding of the molecular processes behind this phenomenon.

The team theorizes that chloroplasts conduct photosynthesis in light, generating energy, while respiration occurs in darkness, using the stored energy. These distinct states potentially serve as symmetry breakers in Caulerpa’s development.

Different light conditions influence the plant’s appearance, as observed in plants exposed to 12 hours of bright light and dark versus those under constant light. These cycles appear pivotal in signaling growth or “rest” periods for Caulerpa.

The scientists aim to explore the connection between chloroplast waves, metabolism, and how they affect the plant’s shape and synchronization among its parts.

The study titled “Macroscopic waves, biological clocks and morphogenesis driven by light in a giant unicellular green alga” is published in Nature Communications. The research involved contributions from Afik, Meyerowitz, and co-author Toni Liu, funded by various institutions, including the Howard Hughes Medical Institute and Caltech programs.

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