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Zygnematophyceae, the closest living algal relatives of land plants come in a variety of forms, including familiar-looking filamentous algae such as the star alga Zygnema, as well as many that just consist of single cells.
Photo Credit: modified from Bierenbroodspot MJ et al. 2026 with permission -
PLOS Biology, DOI: 10.1371/journal.pbio.3004005
Scientific Frontline: Extended "At a Glance" Summary: Deep Evolutionary History of Land Plants' Closest Algal Relatives
The Core Concept: A study analyzing a dataset of over 100 species and 2,000 genes reveals the complex, hidden evolutionary diversity and ancient spread of Zygnematophyceae, the closest living algal relatives of land plants.
Key Distinction/Mechanism: Researchers generated 43 new transcriptomes and combined them with public data to demonstrate that the common ancestor of all Zygnematophyceae was likely a single-celled alga, with filamentous growth evolving multiple times independently rather than through a single transition.
Origin/History: Published in November 2026 by an international research team led by the University of Göttingen, alongside the universities of Maastricht, Innsbruck, and the Museo Nacional de Ciencias Naturales.
Major Frameworks/Components:
- Analysis of transcriptomes representing broad zygnematophyte diversity across more than 100 species and 2,000 genes.
- Discovery that molecular components associated with important plant functions ("land plant heritage") possess much deeper evolutionary origins than land plants themselves.
- Demonstration that evolutionary progression from single-celled algae to complex plants involved diverse lineages experimenting with different body plans and molecular toolkits over hundreds of millions of years.
Branches of Science: Evolutionary Biology, Phycology, Plant Systematics, Molecular Genetics, Bioinformatics.
Future Application: Enhanced phylogenetic mapping and genomic frameworks to precisely reconstruct the ancestral biology and terrestrial transition of early land plants.
Why It Matters: Understanding the complex evolutionary landscape of zygnematophytes sheds light on how ancestral algal lineages developed the genetic and structural innovations that enabled the colonization of land by plants.
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| Spirogyra, named for its spiral arrangement of chloroplasts, is a green alga belonging to the family Zygnematophyceae - making it closely related to living land plants. Photo Credit: Cäcilia F Kunz, Tatyana Darienko, and Jan de Vries. |
What did the algae that gave rise to the first land plants look like? A research team led by the University of Göttingen and including the universities of Maastricht, Innsbruck, and the Museo Nacional de Ciencias Naturales has now taken a detailed look at one of the most important groups for answering these questions: the Zygnematophyceae, the closest living algal relatives of land plants. These include familiar-looking filamentous algae such as Spirogyra, as well as many that consist of just single cells. Despite their relatively simple appearance, they are particularly important for understanding plant evolution due to their close relationship with land plants. Researchers analyzed a dataset covering more than 100 species and 2,000 genes to shed light on the evolution of multicellularity. Their results were published in PLOS Biology.
Previous studies have established that the Zygnematophyceae algae are the closest living algal relatives of land plants, but the evolutionary connections remained difficult to resolve because genomic data were available for only a small number of species. To address this, the researchers generated 43 new transcriptomes—collections of the genes that are active in cells—from strains representing a broad range of zygnematophyte diversity. These data were combined with publicly available sequences to produce a dataset covering more than 100 species and 2,000 genes. The researchers' analysis indicates that the common ancestor of all Zygnematophyceae was probably a single-celled alga. Filamentous growth subsequently evolved several times independently. This suggests that multicellular growth in these algae did not arise through a single evolutionary transition, but emerged repeatedly from simpler ancestral forms.
“Many zygnematophytes look deceptively simple, but their genomes reveal a remarkably deep and complex evolutionary history and diversity. We can begin to see evolutionary events that remain invisible when we study only a handful of model species,” says Dr. Maaike Bierenbroodspot, who carried out this research for her Ph.D. at Göttingen University and is now a postdoctoral researcher at the University of Maastricht.
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| A confocal laser scanning micrograph of the alga Bambusina brebissonii. The chloroplasts autofluoresce in orange, the cell wall is stained blue-green. Photo Credit: Cäcilia F. Kunz, Tatyana Darienko, Jan de Vries |
“These algae have genes that are part of what we call the ‘land plant heritage,’” explains Cäcilia Kunz of the University of Göttingen. “They show that some of the molecular components associated with important plant functions have much deeper evolutionary histories than the land plants themselves. At the same time, their distribution across algal lineages shows that this evolutionary toolkit was dynamic.”
The findings demonstrate why evolutionary studies of the closest algal relatives of land plants require broad sampling. Although the study provides a substantially expanded framework, it still represents only a fraction of the more than 4,000 described zygnematophyte species. “Our study gives us a much better map of the evolutionary landscape surrounding the origin of land plants,” says Professor Jan de Vries of the University of Göttingen. “The more diversity we include, the more we see that evolution was not a simple progression from single-celled algae to increasingly complex plants. Instead, different lineages experimented with different body plans and molecular solutions over hundreds of millions of years. Understanding this diversity is crucial if we want to reconstruct the biology of the algal ancestors from which land plants emerged.”
Published in journal: PLOS Biology
Title: A deep genetic structure phylogenomically frames the closest algal relatives of land plants
Authors: Maaike J. Bierenbroodspot, Cäcilia F. Kunz, Elisa S. Goldbecker, Maike Lorenz,Iker Irisarri, Thomas Pröschold, Tatyana Darienko, and Jan de Vries
Source/Credit: Georg-August-Universität Göttingen
Edited by: Scientific Frontline
Reference Number: ebio110426_01
