Maternal cues, parthenogenesis and life cycle control in Undaria pinnatifida

Author: K_enny A. Bogaert_

Affiliation: Marine Biological Station Carolinensiel, Institute for Integrative Cell Biology and Physiology, University of Münster, Münster, Germany

Kelps are ecologically and economically important brown seaweeds, cultivated for food, feed, biostimulants, bioactive compounds, alginate and biomaterials. Their heteromorphic life cycle, alternating microscopic gametophytes with macroscopic sporophytes, underpins hatchery practice and remains a central bottleneck for breeding: reliable seedstock and strain development are preconditions for the cultivated European algae supply.

We use the Alaricean kelp Undaria pinnatifida (wakame) to dissect and manipulate life cycle transitions. Kelp zygotes develop largely outside the maternal gametophyte, yet stay physically connected to the oogonial wall during early development. Detaching fertilised and unfertilised eggs from this wall disrupts embryonic polarity and, for eggs, strongly increases parthenogenetic development, while retaining even a fragment of maternal wall restores normal apical-basal patterning. Maternal extracellular cues therefore direct basal cell fate and act as a checkpoint on parthenogenesis. We also show that the traits routinely used to score parthenotes, round morphology and a tendency to detach, correlate with detachment itself rather than developmental origin. Building on this, we are extending the work from embryogenesis to the complete life cycle and it’s transitions, including the conditions under which the life cycle can be closed in controlled laboratory conditions.