How Seaweed Became Multicellular

 Seagriculture EU 2024
Multicellular Seaweed

We now know more about how macroalgae became multicellular.

by Alexandra Mystikou,

Recent research into macroalgae genetics has uncovered the genetic underpinnings that enabled macroalgae to evolve and become multicellular, reports

Three lineages of macroalgae developed multicellularity independently, and during very different time periods, by acquiring genes that enable cell adhesion, extracellular matrix formation, and cell differentiation, as published April 12, 2024, in the journal Molecular Plant.

Surprisingly, many of these multicellular-enabling genes had viral origins. The study, which increased the total number of sequenced macroalgal genomes from 14 to 124, is the first to investigate macroalgal evolution through the lens of genomics.

“This is a big genomic resource that will open the door for many more studies,” says co-first author and algal biologist Alexandra Mystikou of New York University Abu Dhabi and the Technology Innovation Institute, United Arab Emirates. “Macroalgae play an important role in global climate regulation and ecosystems, and they have numerous commercial and ecoengineering applications, but until now, there wasn’t a lot of information about their genomes.”

Macroalgae are multicellular, aquatic autotrophs that play vital roles in global climate maintenance and have diverse applications in biotechnology and eco-engineering, which are directly linked to their multicellularity phenotypes. However, their genomic diversity and the evolutionary mechanisms underlying multicellularity in these organisms remain uncharacterized.

To investigate the evolution of macroalgal multicellularity, the researchers sequenced 110 new macroalgal genomes from 105 different species originating from fresh and saltwater habitats in diverse geographies and climates. “We sequenced genomes from diverse climates and phyla, and identified key genomic features that distinguish them from their microalgal relatives,” said Mystikou.

Genes for cell adhesion, extracellular matrix formation, cell polarity, transport, and cell differentiation distinguish macroalgae from microalgae across all three major phyla, constituting conserved and unique gene sets supporting multicellular processes. Adhesome genes show phylum- and climate-specific expansions that may facilitate niche adaptation.

Collectively, their study reveals genetic determinants of convergent and divergent evolutionary trajectories that have shaped morphological diversity in macroalgae and provides genome-wide frameworks to understand photosynthetic multicellular evolution in aquatic environments.

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